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MG MGB GT V8 Factory Originals Technical - Rear axle
|My car has a stock 3.9 MGB rear and I want to lower the revs at highway speeds, even if I lose some acceleration. I also want to keep the car as much "MG" as I can. Has anyone installed the 3.07 ring and pinions that are available in England. Is it a do it yourself job, or does it require special equipment? |
Does anyone have a complete MG axle lower than 3.5 available for sale?
Thanks for your help.
|I heard from one guy who tried the 3.07 ring and pinion and says that it is very noisy. Anyone else have any thoughts.|
|I'm using 3.31:1 out of an MGC|
|I use a C axle that's geared at 3.07. It's very quiet. I would say that people seem to have had better luck using an actual MGC unit than changing out their CW&P to 3.07 ... something must be ever so slightly wrong with the tooling or something on those, because it seems like most people have had really noisy gears when they swap out and it's very hard if not impossible to correct. The MGC rear ends do surface from time to time though they are a tad costly -- but they're wire wheel units which is just what you'd likely want on your V8 conversion, since you can get some reasonable tires under there. Personally I think 3.07 gives you a nice rpm at highway cruise.|
|My car has the 3.07 gears and overdrive on 3rd and 4th. This makes highway cruising a treat, and allows me to bite unsuspecting Camaros and mustangs. Love it.|
|3.07 was standard V8 and there are conversion specialists in the UK, at least, that put these ratios into standard 4-cylinder axles. There is no reason why a 3.07 should be, by definition, noisier than any other ratio if installed correctly, one swallow doesn't make a summer. The factory very soon changed to overdrive on 4th only as the torque reversals in 3rd can be too much for the standard gearbox.|
|The Ford 8" rear end can be geared to a wide range of ratio's. Glenn Towery sell a Ford 8" narrowed axle that has MGB ends that allow you to use MGB brakes. Have not seen his axles, just a thought.|
|The Ford 8" is a great choice. You can get gears of 2.79 3.00 3.55 3.73 4.11 and I am sure even more.. The nice thing is that after measureing my stock rostyle rear end I got a measurment of 52". MOST 60's era Fords with an 8" are that same size!!! All that leave is redrilling the correct lug pattern which any machine shop can perform!!|
Check my site, I just put up a Ford 8 & 9" summary page I found elsewere..
The KEY is to keep you eye open around your area, look in fields, behind garages while you drive down roads, I have been amazed how many cars I see rusting away. Sometimes the people even want to get rid of them but can't afford or don't have the motivation to tow it away!!
|Larry this is great news! I run a 5 lug on 4.5" BC which is the small Ford pattern, meaning that if the spring perches were correctly located one of these axles would be a bolt in swap!! And since the 8" center section is such an easy setup it'd be a cinch to swap in a posi or a carrier with a different gearset. Looks like it's time to go shopping!|
|check those 8" Ford axles- I believe the pinion is not centered. If you use it in unaltered condition, you may have to widen the driveshaft tunnel, move the battery box, mabe more, mabe less. The later 8" have 1 axle the correct length, 1 to shorten to get the pinion centered. At least that is what several people have told be. |
I have 2 8" Ford axles, 1 with way over 100,000 miles that Glen Tower did with MG ends, 1 with Ford ends that Jack @ MG Guys did for me. Both are excelllent, but all I did was order them, not sure of all the construction details.
|Due to the design of the Ford Rear, the carrier mounting is offset so the axle on one side is longer than the other.|
Pricing can vary greatly as well. One trick to due is to look around at TOW yards, not wrecking yards, Tow yards will auction off abandoned vehicles, and I have seen Ford vehicles go for $25..
|Now you guys are confusing me. Is the pinion still centered in the axle assembly and axle shaft lengths different, I hope?|
My 1969 or 1970 Maverick/Comet six cylinder 8 inch rear end has the pinion centered. Just because axles are a different length doesn't necessarily mean the pinion is off-set. The beauty of the Six cylinder rear is that they already have the MGB 4 on 4 1/2 PCD.
|Well you could just get the big 72" long 8.8" axle from a lincoln mark 8 and cut it down to size.... no more offset problems... If you do that, disc brake kits are easy to come, and redrilling for a 4 x 4.5" bolt pattern shouldn't be too hard either.|
Am I really far off base here?
What I was trying to say is that there is no off-set problem on the 8 inch Ford rear end that I used, I didn't have to narrow it and it is standard with the MGB PCD, so the axles are totally stock if they ever need replacement. Why go to a bunch of trouble and expense to narrow the differential if it is unnecessary to do so?
If you're looking for disc brakes, why not look for a late '70s - early '80s rear axle from the Lincoln Versailles. They came equipped with factory disc brakes - with 10 1/2" rotors I seem to remember. The axle would have to be narrowed though. I'm sure it is more than 52".
|Would it really be that hard to swap to disc brakes on the early axle? I mean, all you've got there is a 4 bolt flange on the tube end and the axle flange, 4 or 5 on a 4-1/2" BC right? Wouldn't there be plenty of parts around that would just bolt right up? How hard could it be?|
|You can pick up a brand new ford 8.8" rear axle with full disc brakes, 3.72:1 ratio with positraction off ebay for about $500.00 Even if you have to have it shortened, how can you go wrong there?|
George: I'm definitely in favor of the KISS method of building these cars, but the idea of buying a rear axle from a vintage 60's or 70's car kind of scares me. Parts availability? Quality? A 35 year old axle is either a) going to have a lot of miles on it or B)have sat around for a long time in mud, rain, or other unfavorable conditions, and that can't do anything for the quality of what's inside. Especially if a few rubber seals deteriorate, your oil leaks out, and it's downhill from there. Someone is probably going to find a good one for a cheap price, but man, what a risk. Ford 8.8's are cheap and plentiful, just do a search on ebay, there's every gear ratio you could ever want available!
I hate having to make choices between parts on this car. Why can't there just be 1 part that works?
|George B. I see you're in CA, I'm doing a conversion and would like to have a local to trade ideas. E-mail me please. Morgan (Fullerton CA)|
I thought I'd put my 2 cents worth in. I tend to agree with you Justin, however, it all comes down to what you can afford. I went for a low mile for axle but still had the diff checked and the bearings replaced.
What you can do with an offset type diff (as I mentioned in another thread) is only shorten the long side of the axle which cuts the machining work in half. I am not familiar with your 8 inch and 8.8 inch axles, but reckon you might go close to the correct width doing this method. In fact what they do in Adelaide here is throw away the axle from the longer side and get another axle shaft from the shorter side and just shorten the housing.....no resplining at all which can again reduce cost.HTH
|Hold on now guys!! :-P|
In terms of durability and part, here in the US the Ford 8 and 9" rears are about the most widely used, sought and coveted rears you can get. Parts are available in place you would not even imagine.
I was originally going to go 8.8" like is being spoken of and yes it comes to $$$ $500 is allot of $$. I hope to have my 8" ford bought and narrowed for under $200 if not 150. Finding a local guy to narrow and redrill is key, though I will be looking for that commet rear end..
So is your commet rear the same width as a stock B rear?? 52" drum to drum?!?? I am unsure if maybe you are using different wheels which could take a different offset. so please let us know
The Comet/Maverick is about 56 inches, and as you guessed, I handled it in the wheel off-set, as I was having wider rims installed on my center sections anyway.
The people I've seen using the short axle and shortening the long side to match did it for cosmetic purposes so the pumpkin was centered; this will put the pinion off-center on most rear ends. I did this on one swap when I wanted the engine off-set to the right for steering clearance. The engine off-set helped to balance the car when there was no passenger aboard.
That is what I was afraid of. I have a doc on my site that says a whole bunch of axleas are 52" but I have a bad feeling that is to the backplate, not the wheel mounting surface. I have also been told by a few people that many of the numbers are incorrect, so I may just pull it off the site. I know from my 2hr junkyard stroll last weekend that most of the axles (even on small cars like pintos) were 56-60". I think I will probably just go grab that capri axle I saw and be on my way, maybe after I experiment with my MGB rear a bit more though..
I think this whole offset pinion is a bit misleading to some people. If you look at a Ford 8 or 9" just at the carrier, the pinion is set off to one side of the big dome housing, also the diff sits off to one side, thus you have one short and one long shaft. However if you measure from the spring perches, flanges, or drums to the pinion you will see that it is centered.
What offset is your rims then?? Isn't 2 inches per side a whole lot to take in??
|Offset: I'd guess that mucks with any chance of rotating tires.|
What's the deal with the Capri axle?
I'm asking a correspondent to measure his spare Mustang axle.
|You can't rotate the tires with different sizes front and rear with radial tires, so to me it was a non-issue. With rims two inches wider than stock, the added offset can't be seen.|
|I too was looking at other axles (just dreaming of completing a V8 conversion). Another axle option to those of us in the US is the chevette axle. It already has the panhard setup and I think that they are narrow enough. I know that I have seen numerous ads for complete chevettes for only a couple hundred bucks. With all the mods that I have heard people talk about on this list I would imagine that it would not be difficult to adapt the chevette rearend to work with the MGB.|
|The Mustang 8" measured out around 51-1/2 between the backing plates. Too big.|
|Well, any Ford 8" or 9" axle you get will have to be shortened, there is just other way..|
Chevette? I would not touch one of those, all Chevettes were 4cyl, not built to handle serious power, just not worth the effort to modify to fit a MGB.. might as well as stick with the B axle..
I have a big question, what is to say the MGB axle is not strong enough?? I have mine apart to fix a problem (PO skipped a thrust washer, and a bad bearing.) Holding the axle shaft it looks every bit as thick and strong as a 8" ford axle shaft. Are there any specs on torque ratings it can take?
I am just going to fix this one and run it till it blows, it has held up to some HARD 1/4mi runs.
What about gearing?I am toying with maybe getting one of the 3.07 gearsets. Anyone have any info beside how much of a pain to set-up they are?
|Larry - I agree - the strength of the stock MGB tube axle has not been seriously questioned - the gearbox and propshaft (UJs) were the weak links - and then only if you are messing around with more than about 150BHP.|
It's disappointing if the replacement CW&P set is noisy - but then one wants to be sure that the problem is not in the setting up - that's one of those jobs that easy to do badly.
As a footnote for those putting V8 power through the 1800 drivetrain - remember the factory upgraded the UK gearbox and (possibly) the diff oils to cope with the effects of the extra power.
|To repeat: Little Joe Huffaker claimed the stock MGB axle was good for 175 hp in a race car. I pretty well abused one behind a Buick 215 with the hot Competition Cams stick, Holley 600 double pumper and those big tube headers with glass pack header mufflers running through both a wide ratio T-50 and later a close ratio T-50, and 265/50-14 BFG TA's. The only damage it has suffered is wear of the thrust washers. I think the key here is that the car does not hook up like a 1/4 mile machine. Which is not to say it isn't fast, just not set up for maximum weight transfer. Between the hot Buick, the turbocharged Olds 215, and now the blown and injected Olds 215 I think that's a pretty fair test of durability and I'm waiting for one of you Ford or 300 Buick guys to take testing to the next level. Will the gears hold up as well as an 8"? Is the carrier as durable? Of course then the cost of a posi is so high that axle replacement becomes a viable option. In the meantime, I have two spares, should I break one.|
On the subject of gearing: I'm not quite sure what you fellas are trying to accomplish with those 3.07 gearsets. I run the stock 3.9's, a close ratio T-50 which has about a .8 overdrive 5th and 24" diameter tires, and the car is still capable of speeds in the neighborhood of 150 mph. True, at 70-80 it'll be ticking over about 3 grand but that's nothing for such a short stroke engine, is dead smack in the middle of the powerband, is well up the torque curve, gives absolutely instant response and great power for passing and hills, and being reasonably close to the torque peak should give good economy. Plus it launches exceptionally well, and the shift points are reasonable. If I was to go to a 3.07 all that would go to hades in a handbasket. Acceleration would plummet, shift points would be stretched out to the point of yawning, economy would likely suffer, overtaking would require a downshift, and the top speed would as likely as not drop. Is this just for the sake of dropping engine speed at highway cruise to the 2200rpm range? Think a little bit about the engine you are abusing by doing this. It's stroke is shorter than the stock 4. It's a small displacement (potentially) high reving motor, and unlike the SBC it will be happier at 3 grand than at 2 cruising. Sorry guys, I just can't see it. When I was a boy my dad got the bright idea to order a pickup with the lowest gearset available. What a mistake. That miserable beast was excruciating to drive. Right now I have a gearset in my tow vehicle which is only one step below optimum, and it's OK, but moving back up only one step would make such a world of difference in the fun factor that I'm going to have to do it at some point, even though it's got 2 diffs, used original 4.56 gearsets aren't readily available, and they are Dana axles. If you've got to play with the low gearsets this way, then I do highly recommend the 8" axle. At least that way you can set up another 3rd member on the bench and swap it out in a couple hours time.
|Some of the early Bronco 8" rears are 46 inches flange-to-flange (see http://www.ridgenet.net/~biesiade/Fordrears.html if you can believe everything you read).|
To try to answer your original question, if you want to keep the MG rear axle, try to find a 3:31 cwp set out of an MGC rather than the 3.07. I too have felt that 3.07 was too low. The 3.31 can be tough to find, but try John at Autogear in the UK; if anyone can locate what you need, it's him. As to a DIY job, no. The gears have to mesh at exactly the right place and this takes experience, or you've just wasted a bunch of money. Finding an expert to do the job is not that hard or expensive; just about any metro area has somebody, although you may have to ask around a little.
|I checked with my local machine shop, they say it's no cheaper to cut and respline an axle then it is to buy new ones from mosier. I questioned them about tube length at that point, and they didn't have a good answer. That's a pretty good question. You have to cut and weld that tube DEAD ON or you're gonna have a bearing nightmare in the future. What are people doing about getting tubes shortened and actually having them be straight?|
Jim raised a good point about the rear axle ratios, and while I LOVE my 1-4 gear acceleration, I wouldn't mind 5th being a little lower on the highway. 3200 rpm's at 70 mph does seem a little high to me, but then again, I'm not used to V8's and what makes them tick. Between all this axle crap, and the IRS thread going on right now, there's a lot to chew on. Both methods seem to offer some benefits, but have equally as many drawbacks.
|Allan, one other thing that needs to be mentioned if you do locate and decide to use the 3.31 gears from an MGC in an MGB rear axle, is that there is some additional machining that needs to be done to the gear carrier. John knows the particulars of this. And if you go this route, you'll probably spend 50% or so more than if you use a Ford or some other kind of axle, which may already have limited slip installed.|
|Hmmm, personally I think 3.07 (w/the .83 overdrive of a Rover 5-speed box) is just fantastic. Nice loping feel on the highway. The main consideration has to be your cam -- which one you select and how much you advance/retard it has a huge amount to do with appropriate gearing. Remember, the Rover V8 even with a stock cam hits its torque peak below 3K rpm. You can advance your cam by, say, 4 degrees and get the power to come on at 1500. What's not to like?|
(Also: guys, let's get our terminology straight, just so we know what each other are talking about. A 3.07 rear gives you a HIGHER gear than a 3.9, not a lower gear! Lower final drive ratio --> higher gear.)
|I hate it when someone picks nits this late on a Friday afternoon. 'Taller' gears, or physically larger ring gears, make for a higher ratio between the cwp set, comparatively, making it a 'lower' gear. Go figure. TGIF.|
|My latest road trip of 1100 miles to the V8 convention was in a 215 roadster with a 3.70 MGC rear axle. Road speed of around 70 mph was very pleasant with .63 5th gear around 3000 rpms, 15" wheels. Good (a relative term) gas milage, plenty of power for passing without down shifting. |
The MGB/MGC rear axle is very strong, a Dana unit, with big shafts & bearings. I will be changing to an 8" Ford for gear selection when I change to the 4.2L engine, as this engine will perform better with a 3.55 rear, not because the MG axle is a week link. I believe that for a typical conversion, driven as most of us drive, the MG axle will deal with well over 200 HP.
|3.07's are for 3 reasons. |
1. to be able to use 1st gear again.
2. to bring down cruising rpm to the sub 2K range for better economly.
3. Allow me to keep out of 5th gear on my drag runs which will further improve me 1/4 ET..
Now on durability. I talked to my local shop guy, he said after many years of hard racing use the only weak point on the MGB axle is the roll pin that holds in the pis with the diff spider gears.. There was a guy in the UK making some special durable roll pins. If you really look at it, to use a MG rear requires using a small rear UJ THAT is the weak link.. I have a 12-20 which is a Ford Ranger truck UJ, but not a 13-30 which is a stock mustang one.. On my 1/4 mile runs I was slamming it into gear and breaking loose all the way through 4th gear, so I think that is a pretty strong test..
V8 are not spin motors like the stock 4cyl motor.. The stock motor loves to run 4K, but V8's while they go up to 6K do not "like" running that high for long periods. It will make lots of heat and you have allot of wieght spinning fast.. My car runs under 3K $ 70mph as it is, with 3.55 or 3.0 she will be in the 2K range..
|Just wanted to thank everyone who responded to my question. What an incredible wealth of information!|
The consensus (less one) seems to be that the B V8 is just a better car all around with something like a 3.3 or 3.07 rear. The only question is what is the best way to get it done.
Thanks again, guys.
|Allan, if you can find/make friend that are into cars especially ford, would recommend the 8". Guys will have carries and gears sitting around and it is not uncommon to trade the entire carrier assembly which means not hassling with setting lash etc..|
They are still fairly readily available in yards too, I walked a local wreck last weekend and found a good 4-5 units $100 each..
|I know I'll never convince most people, that's OK. It gives me an edge when the pedal hits the floor, and makes a goodly difference in the fun factor. Never over (or is it under?) gear a performance car.|
How low is your gearing?
My Fi is vitesse based, 3.08:1 axle and 195x65x15 tyres.
55Mph is 2000revs, after some experimenting with tyres and axles, I find this the best compromise for me, it will just run at 30mph (about 1100rpm) around town, and cruising on motorways gives me 30(imperial) miles per gallon, and our UK speed limit is just over 2500 rpm, so the engine should last forever.
I have a Chrysler 8 3/4" with 3.23 gears and posi. Since it was out of a full size car, it was narrowed 10". The machinist that norrowed it, chucked the whole housing (minus third member and axles)up in a large lathe. At the point where the cuts on the tubes were to be made, he built up that area with bead welds and then machinced the built up area down to true it up with the true center line of the axles. Then the tubes were cut and flanges welded back on at the new "trued" location. He had to do it this way, because the axle housing is a stamped steel unit and the outer dia. is not true to the actual center line. He did cut and respline my axles, but it would be easier/cheaper to by axles from Mosier.
I had all this done back in 1983 and have absolutely zero problems with the rear end the past 19 years! While the diff is probably a little stronger than required, I find the 3.23 ratio just right.70 mph w/.73 5th is at 2350 rpm and first gear is very usable. I ended up going with the chrysler 8 3/4" because of a wide choice of gear ratios, lots of them came with posi, and the axles are not retained with "c" clips.
|Well all. It is finally time. The MGB axle is done for!! I rebuilt it last weekend and used an old timers trick of putting a extra thrust washer in to stiffen up the action. It worked for about a day and a half, and man was it a fun day!!! If anyone remembers the old Magnum PI TV show, I did a couple of takeoffs like he did from the grass in the openeing credits, only I was on dry pavement!! YEHAA!! But after 150miles it had lossened back to normal action.|
It was a valiant attempt, but alas the spider gears in the diff could not take the onslaught of 300ft/lbs of torque and good traction. Shifting into 3rd on a spritied run and BANG! I had no power to the wheels!!
SO, now I am on the lookout for a donor vehicle/Axle, so I though I would bump this thread up to the top and see if anyone else has made a decision. I am actually leaning toward 8.8 a little due to that most are Trac-loc. I can get either a 8 or 8.8" for $100 complete drum to drum, what do you gus think??
|I would. Get the disc brakes, posi, and in my case, stick with the 3.9 ratio, as I like it a lot. If I thought I might be changing ratios though I'd lean towards the 8".|
|I always suspected the spiders might be the weak link. Thanks for confirming it. Easier to swap in new spiders than another B axle.|
|All this talk enticed me to the salvage yard....|
Volvo 240 diesel rear end...has 3.31:1 gears, disc brakes, & is almost the correct width...whack off all the Volvo brackets, weld on MG ones, change out the emergency brake setup with one from a series-7 Volvo & I may be onto something!!!
|Jim, MGB Spiders get $$$ fast.. I would much rather take the $$ and swap to a 8 or I am leaning toward a 8.8 as they come with Trac-loc in mustangs.. Those 2 days of running semi locker were very informative on just how strong my motor really pulls..|
Then a set of 205/60r14 tires and I am off and running with the stallions..
OHH, just a word of caution, Our cars may be fast and all, but watch ouf the the late model LS1 Firebirds and Camaro's, they are REALLY fast.. heh
Sounds like you had fun. I think you're on the right track with the 8 or 8.8, although I'm not familiar with the differences. If you're gonna blast off like that, I don't think I'd invest in any more spider gears by themselves.
|Nah.. That rear end is destined for my MG trailer, so breaking the spiders actually save me the work of having to remover them!! HEH!!|
I am leaning to the 8.8 because in stangs they come with trac-loc (Fords version of posi) I will let you guys know how it goes.
Okay, you broke a semi-worn out MG rearend, but I'm not convinced that the 8 inch Ford is going to be much stronger, if any.
The 8.8 inch is definitely stronger. It should be, I believe Ford "borrowed" the design from the 12 bolt Chevy. The down side is that it looks to be much heavier than the MG or 8 inch Ford.
The 8 3/4 Chrysler that Bill runs is a good choice. I don't know the weight, but I have a friend that has used one in a '57 Chevy for a long time.
|If you are still looking for the type of rear you want, have you considered a Dana out of a postal jeep? I know I am still looking for one. I found 5 postal jeeps in a jy, but all have the smaller rear.|
|No, I have pretty much decided on the 8.8" just waiting for the "right deal" to drop in my lap. The 8" is a bit tougher in that is has an extra bearing in the pinion assembly which helps strength and the spiders are made to take V8 punishement. Other than that though I will say a MGB is just as strong in the other areas, the axles are the same diam if the MGB is not actualy thicker..|
|Today I weighed my stock 1979 MGB rear axle with drum brakes, brake tubes,tee and hose (to body),spring seats, and one pickup strap. WEIGHT: 164 Lbs. |
I also weighed my narrowed 1995 Ford Mustang 8.8 inch rear axle narrowed to 52.00 inch wheel mounting surface to wheel mounting surface, 4 stud, with stock Mustang brake disks and calipers,MGB style spring pads, and as much casting material removed as possible without sacrificing strength including the two top locator bosses for the short rods to the Mustang body and the carrier flanges which had come with a heavy damper attached which has been removed also. This rear axle has limited slip and a 3.55 Motorcraft gear set. WEIGHT: 168 Lbs.
Note: These were weighed on the same scale.
Thnks for the info. I was going to do the same thing once I got my 8.8!! 4lbs is not bad at al for a axle that will not ever break under your car.. These new 8.8' are even stronger than the old ford 8" and I think I heard very close if not equal to a normal 9". The built in trac-loc found on most mustang units is a great deal too!!
What did you have to do to get it shortened, did you do it your-self or farm it out? Let me know I am going to shorten mine to the same size, and have the spring perches mounted to get the wheels recentered ion the wheel wells as my chassis is off by 1/8" to the passenger side. Then I go buy that set of 205's and live happily ever after..
|I think I'll do that too. The posi and disc brakes would be good, and I can use the Mustang 5 lug pattern as is. Time to visit the Ford yard. What's the closest ratio to 3.90?|
I would recommend going with a lower gearing than the stock, unless you have driven it allot and like not using 1st?? Though I am not sure how your car is set-up, that is the biggest complaint about the stock axle, the lame ratio when paired with a T5. I liked mine at 1st, but soon realised it's limitations and poor gearing combo when used with my T5.
You can get all the following for a ford.. 2.73, 3.08, 3.27, 3.55, 3.73, 4.11 I would think there is a gear between the 3.73 and 4.11 but I don't know what it would be..
Download the excel sheet off my website and you can play with different gearing and tire sizes to get a good idea how it will lay out..
|Thanks Larry, but I don't need to. I've run this combo for over 15 years now and like it right well. T-50 close ratio, 3.90 gearing, 265/50-14 tires. I hit 2nd on the other side of the intersection and 5th keeps me in the powerband. I just think a stronger axle might be a good idea with the blower. Of course, it did turn out that I had broken the wide ratio T-50 years ago about the time I switched to the CR, so maybe I should have a look at the gearing again. Might want to think about a stronger gearbox someday. But for now it's a good combo. Got the gears I need when I want to run hard, and if not I can just pretend it's a 4 speed and have one less gear to worry about. With the road race shift pattern 1st is only ever used for launch anyway.|
|heh it must bee the tires making the diference, with mine I barely get the front tires acrost the line before I have to go to 2nd, I mean it is THAT bad.. I WISH I could haqve gotten out there and seen you car in person..|
I got a couple tweks I hope to do this winter that I am keeping under wraps for now, but hopefully it should be a brave new workd come spring..
|HI, Larry and all, When I put this info on the BBS,|
I was more concerned with the weight reference only.
Itís been about a year since I was working on this
area. The actual width of my rear axle is 51.75 inchs.
I had it narrowed at Moser Engineering in Portland,
(sorry) Indiana. They narrowed the tubes and recut
the existing axle shafts. They did not do spring pads
or traction bar mounts,etc at the time I dealt with them. Their web site is:
By careful with your rear axle width. I still do not
have my axle on the MGB. I know my disk brake
parking brake return spring overlaps the rear spring
by .75 inch- just above it. I had Moser revolve the
rear rotor mounting holes down to miss the MGB
sheetmetal but I had to keep that return spring above
the spring top surface. Right now I am a little close
and may have to put a shim between the axle spring
pad and the spring. My pinion is located .25 inch off
center toward the driver side. I have no driveshaft yet so Iím not too sure how that will work out either. I donít have my traction bar parts yet either. Iím planning on using tube shocks. I suggest you get the axle and try to simulate all the onditions you will run into as best you can before you have it machined.
|Good suggestion. I should have plenty of time to sort it out, as I have up to 3 sets of spare spider gears I can use if I need to, and 2 entire spare axles. (I narrowed the 3rd one, which is a banjo style, for a lawn tractor I never built.)|
Larry, the difference is in the gear ratios of the T-50 CR. I've packed away my back issues of the V8 newsletter for the move so I don't have the charts for comparison, but to give you the feel for it, the wide ratio was like what you are describing. Good for a h*ll of a hole shot if you had a high winding engine but almost like double clutching going through the first two gears. Lots of wheelspin too, good for impressing yer school buddies but not the fastest way to launch. The CR is quite different. I did a ratio comparison some time back in the newsletter in support of the T-50 as a good candidate for a V8 swap, but they seem to be getting scarce. There was even a T-50 with a 1:1 5th gear and the ratios are superb when combined with about a 3.31 or 3.08 axle ratio, but I've never seen one, and I wonder about the strength of the 1st gearset now that I have learned that I had broken the WR. (behind a heavily built Buick 215) The 1st gear ratios would have been very similar.
But don't keep us in suspense Larry, how about a hint on those mods?
|reat info guys!! I am shooting for 52" mount to mount. I will also probably do it to move my pinion .25 or more toward the driver's side fron were it is now.. As it sits I had to get a smaller tube DS as it was hitting the parking brake. This is due to the MGB axle being offset 1/8" to the passenger side. |
Sorry Jim Some things are better appreciated with a bit of suspense!! I don't have everything lined up for the big change, but aside from that she will see modifications to the front & rear suspension from what I had and changes to cooling system. As it sits the motor is torn down to just the long block already for the work this winter.
No worries though I am keeping a chronicle on the big change like my other pages, but it will not be published until it is all done..
Please pardon my ramblings as I quickly throw in my two cents worth...
It's been several years since I put the axle from a '92 Mustang under my MG. It's an 8.8 Traction-lok with 3.27 gears and drum brakes. I had Moser make new shafts and a local drag-race shop narrowed it for me. (They already had the fixtures to do it right.) My local Spicer shop made and balanced a new driveshaft for me during lunch hour one day - for less than a hundred bucks! They also sold me wedge-shaped aluminum spacers I needed to fine tune the angle of the input shaft. Of course it needed new U-bolts. I had a friend in the business who got me some good ones. (I think they were heat treated after being bent.) I like the 3.27 gear ratio incredibly better than the previous 3.909 (which was awful and which I put up with for way too long.) The 8.8 axle works great, but I still haven't got the parking brake dialed-in right. The cable routing was tricky. I think I have too much friction in it at some point, so it takes too much muscle to engage. In my opinion, fitting the parking brake cable was definitely the hardest part of the installation... Cutting and grinding dead weight off the axle was the fun part.
Thanks for the input!! how do you findt hat trac-loc behaves?? corners smoothly etc??? not trying to lock and skip around?? I have 3.27's and 3.08 gears here waiting to do my axle swap..
|One diff you guys should look at is Jaguar MK11,its made by Salibury so looks same as MGB, It has LSD ,4 ratios i think -3.31, 3.54,3.77,[& 4.2 but without LSD] someone can confirm.Axles are thicker & stronger than MGBGTV8. Tailshaft flange same as MGBGTV8 & MGC[ larger dia' than MGB], has mga twin cam disc brakes & for MGC boys -bolt on hubs are to same bolt PCD pattern as C. Axles & tubes need to be narrowed,Jag suspension mounts removed & rewelded with MGB ones, & MGB hubs put on instead of JAG/MGC pattern hubs. Works TR8s used this diff,; I be using this diff in my Historic racer MGCGT as i heard too many stories of Ford diffs blowing up with 250bhp+,Regards STEVE|
What ford diff are you talking about blowing up wuith 250bhp?? 8" and 9" are rated WELL over tht amount.. I know guys getting 500hp in big fat cars with 8" units.. and the 8.8 and 9" are almost indestructable.. we have guys with 600hp 9second mustangs running stock 8.8's with C-clip eliminators..
|NASCAR runs 9" Ford axles (these guys get a bit over 250 HP, I believe)|
|Stephen, is that Jag Mk2 or Mk11?.|
Are you saying stock axle has LSD fitted?.
What type? Clutch or gear?
Looks interesting to me and my MGC!.
I looked at this as a possibility when I built my V8, but couldn't get my hands on a MK11 Jaguar axle.(I was told to go for the XK150 version) They must be quite rare now , and therefore expensive. I settled for a cut-down Rover SD1 vitesse axle, it's proved OK to date, but the half shaft splines are starting to twist, and I had to alter the diff from 2.9 to 3.07 as it was too high around town in 5th.
|CHRIS. Jag MK 11 /2 /two is around 1962-64 model like crooks used on U.K movies, looks similar to Jag mk 1 before it. It has clutch type LSD & MADE by Salibury like MGC diff i'm sure. Larry ,Ford diffs having problems were 8-8 3/4?, i think it was way it was modiflied & put in B diffs , plus lot were second hand & may have been on last legs;if new units were added maybe they last, but most people try to modify on the cheap & suffer for it later,power costs money so how much power can you afford ; i like to do something right first time as i'm sure most people would, but i like Jag diff as close to M.G diff in originality as you can get compared to Ford diff. STEVE|
|Well, I went for a Ford 8.8. If it works for 600hp Mustang guys I think it will be more than sufficient for my little MG with half the power. Plus by going with the "new" unit aftermarket parts are readily available, like gears, posi, stiffer axles, bigger brakes..|
Plus I got it for FREE, just need lots of clean up and to be shortened and redrilled, which I can do in house.
Quite honestly it comes down to what is available in your area. Ford stuff is easy to find here in the US, not sure how easy they are to find over in Europe..
Just so I understand: it sounds like you're saying the Achilles heel on an MGB axle isn't the assembly itself, which is plenty strong; it's rather the flange setup on the front of the pumpkin. Is an MGC axle similarly configured, and would it face the same problem? My personal overwhelming preference would be just to use an MGC 3.07 axle and rebuild it. It's going behind a rather serious Rover 4.2. Is this just a waste of time and money? Is a C axle stronger than a B unit, or are they exactly the same?
And what the heck is this roll pin thing everybody keeps talking about??
not sure who your ?? is aimed at but I will give you what I know, from a MGB shop guy I talked to and my own experience.
The MGB housing and axles look to be every bit as stout at a Ford 8" Similar bearings and layout, axle shafts are the same diam or very close. This is from my personal observation of the units. Based on what I see in my 8.8" the diff carrier bearings are actually the same units! The MG unit made in England and the Ford from Japan. They have the same bearing number listed on them! This attests that the bearings in the MGB axle are up to the task.
My MG mechanic said in the old racers they had problems with a "roll pin" If you have had a MGB rear end apart to replace the thrust washers you have dealt with this pin, it is the small hollow steel pin that holds the shaft with the 2 small spider gears. The mechanic said on the top race cars these pin were prone to breaking, then the shaft would flty out hitting the housing KABOOM in a big nasty way. So leyland or the race team had special one made to combat this.
When I broke mine I did not twist a shaft as I have heard happens, nor did I break that roll pin. I quite simply shattered the 2 small spider gears. Now that said I was running her very hard. I know many V8 convertors baby thier carts, and that is fine, I built this car to have fun with and run hard otherwise I would have stuck with the 4cyl. I want to take her to the track whne I can and just flat out romp on it. This is my hot-rod, muscle car. When she broke I was shifting to 3rd gear down track and probably dumped the clutch between 1000 and 2000rpm, which means she saw probably in the nieghborhood of 300+ft/lbs of torque, not something leyland ever though the rear end would see.
The flange you mention is also a possible issue. It does not have to do with the flange itself being weak, but that that flange limits the size of the U-joint that can be used in the driveshaft. I was able to find a special flange through Spicer that matches the MGB rear end flange, but it is limited to a 12-20 size ujoint. That is bigger than a stock MGB thankfully, but not as big as what comes on stock V8 vehicles which is usually a 13-30 or larger. That Ujoint could be another potenital weak point.
Anyway that just my $0.02 hope it helps..
|I wonder just how strong the 8" axle is. I would think that in a car the size and weight of the MGB it would be adequate, and the great advantage of that axle is the ease with which the third member can be swapped out. This leaves the door open to experimenting with different gear ratios and positrac units. That is of some importance to me as I am beginning to think that a more up to date transmission than the T-50 might be in my future. I would like an easy shifting transmission, which the T-50 with a shortened shifter is not.|
My understanding of the weaknesses of the 8 and 9" Ford axles is that the housing lacks stiffness, resulting in more rapid ring/pinion wear under hard use, but that the racers counter this by welding gussets into the inside of the housing between the mounting flange and the rear of the housing. Probably every axle ratio and every posi unit ever made .
can be had for the 9" and maybe the 8" too, and parts still seem to be pretty cheap at the swap meets.
I have used MGC axles in 2 of my V8 conversions without problems. The MGC flange is larger than the MGB piece, & uses larger U-joints. With 14" wheels, I used both a 3.07 & 3.307 ratio rear, with 15" wheels, I am using a 3.70 C rear behind a T-5 with .63 5th gear.
The only problems with the C rear are availability & the fact that virtually all are wire wheel units. Using the wire wheel rear with steel wheel hubs is actually a plus, as it allows for wider tires & wheels.
Finding a 3.07 or 3.307 rear is blind, very good luck.
Any C axle you find will probably have over 100,000 miles on it, & a shop rebuild will cost around $700-800.00, so economically, a narrowed 8" Ford may make more sense.
|What you guys need is a Mack truck axle. Perhaps it will be strong enough for you 250 hp V8's|
This thread was discussed between 13/08/2002 and 12/10/2002
This thread is from the archive. The Live MG MGB GT V8 Factory Originals Technical BBS is active now.