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MG Midget and Sprite Technical - gearbox replacment advice....

Ok, my gearbox is making bad noises and is on it's way out (again)
I need a better unit as my 1430 Mk3 puts out over 100bhp.

Maybe a 5 speed is in order, I don't know.
I dont do much motorway driving but the car is used everyday.
I know there are various conversions out there, whats your feeling guys?




Mallorcaben

nothing beats a cleen crisp ribcase gearbox
and a proper rebuild sould be able to take the power

I hate the 5 speeds for they never have the right gearing and have strange places for the gearleaver (shifting with your elbow isn't all that)
o Könemann

Nice tidy car.

The Ford 5 speed is available with a diverse range of ratios such that you CAN have the right gearing. It's also possible to have the gearlever moved forward so that you can still strike your knuckles on the bottom of the dash/radio console/aux instrument housing.

You can also have a co-axial hydraulic clutch slave fitted to the Ford box.

Daniel Thirteen-Twelve

"You can also have a co-axial hydraulic clutch slave fitted to the Ford box."

Like this one

The best ever mod to my car with the five speed, which for me has ideal ratios and a gearstick that sits just far back enough to allow the radio or tape to be used easily.

And now I have the 5 speed I can hear the engine, the back axle, the radio and the missus.

Even other cars...


Bill

Frontline kit works for me, completely changed the car for me, and made motorway driving very easy, and the one mod that should be done to all midgets but wish I had known about the hydraulic slave unit.
Alex Sturgeon

That is a modifed Burton Engineering adapter redrilled to suit a very cheap "pattern" Saab 900 concentric unit

Solved a lot of issues I was having with pedal "tramping" as the pedal swung the fork in place across the fingers on the diaphragm clutch when taking up drive

I broke two clutch pressure plates due to excentric operations before I realised the problem
Bill

Hi Bill,

Now you tell me! I partially ruined a clutch pressure plate before fitting the co-axial slave - just over 600 miles. The problem for me co-incided with the first time I had run a bearing direct on the clutch fingers.

I'm using the Burton slave with a spacer and modified hoses (45 swivel fitting on the bleed line on a male/male to the slave).

Daniel Thirteen-Twelve

Bill, do you have the detail on the Allen caps you used on your bellhousing - they look a lot neater than what I have on my car.
Daniel Thirteen-Twelve

Daniel, those cap heads were supllied by MMC when I bought the bellhousing. But they are standard Metric cap heads I understand.

MMC specifically warned me that the hex headed bolts would foul as they tightened up.

The capheads protrude slightly inside the front face of the box and so I have added thread lock to prevent oil leaks

I am considering writing up a definitive "this CAN go wrong, so do this" article to help others when contemplating the change over. There is little said about the diapgragm versus BMC clutch fork in a Ford box interface and the trouble one CAN get into is there?
Bill

Bill,

AFAIK they are not standard metric socket head cap screws (SHCS) as the thread in question on the Ford box is M12x1.5 whereas the standard metric coarse which is easy to get in SHCS is M12x1.75. The Caterham fasteners I got were hex head but were tight in the bellhousing and required I turn down a socket to get clearance to do the bolts up.

Regardind your tramping and overthrow of the clutch I would consider that poor development of the conversion.
David Billington

That is interesting David

I will look into caphead availability on Monday

I agree the development was a "little" undeveloped too, but as I was doing it "on the cheap" I wonder if having all of the MMC kit would have precluded the faulty bits I suffered...

I think a real write up is called for, pros and cons to be listed and fixes for whatever occurred to be listed.

For instance Arie seems to have had some problems with the Frontline equipped type9 / K series interfacing as well as some of us A series-ers, Guy too has come along the same concentric route for similar reasons. Guy has used different "source components" in his adaptation. Listing all the known methods could be of great use for those contemplating the change.
Bill

I've written up my experiences with the Burton co-ax kit and 5 speed including the detail of the weight saving.

I'd not had any clutch problems using the Ford 5-speed until switching to the latest design of 7.5" cover which is the first time I've had a cover that does not have a central release plate and thus the bearing runs directly on the fingers.

Remember MMC invented the Ford 5 speed conversion and cast the bellhousing. Frontline uses MMC parts for the most part. Frontline use a different fork or bearing and retain the whole sleeve while the MMC is pure Spridget.

Until Bill's post my informed knowledge was that I was the only person to have problems of this nature - cover failure

Bill, I'd be interested to see photos of your failed covers to see if they failed in the same way as mine. My own damaged cover was most definitely not overstroked (if this is what you mean by overthrown).

The Burton co-ax cannot overstroke the plate, at least not with the later clutch master as it produces nearly exactly maximum travel for a single pedal depression. It's possible to measure this before the gearbox goes in the car.

Daniel Thirteen-Twelve

Hmm, the cover on mine is a 6 and a half inch unit, but without a centre pad, so it doesn't seem the problem is restricted to larger clutches.

And I have the twin master cylinder (1966 vintage)
in Lara which does worry me a little on the over throw issue but the clutch operates with about a half inch of pedal movement between "on" and "off"

The picture shows the spring finger distortion I found at the second time of failing as well as the gap in the diaphragm spring plate that ensued

(about "ten/eleven-o-clock" on the knackered clutch plate circumference)


Bill

I hope this hijack is helping Mallorcaben with his problem, seems to deserve its own thread really.

I would point out that unlike many I DO enjoy a high speed motorway dash, but the five speed equally comes into its own when used on the sort of roads we would call Spridgety roads with many a "downshift and rushaway" twist and turn.

My type 9 is fully at home in both kinds of driving, I'd hate to have to go back to the noisy ribcase box.
Bill

First time I have looked in on this thread as for some reason I thought it was about choice of gearbox!

My initial problem was clutch cover damage. Distortion of the diapragm fingers caused by overthrow. Exactly like Bill's. This was on a 6 1/2" cover and with a MMC Type 9 bellhousing and their simple fixed fulcrum lever operating a PM type roller release. At first I just replaced the clutch cover.

Shortly after this I began to get a lot of chatter from the release bearing thrashing around and bouncing off the splines of the input shaft. This was again due to the design of the fixed length operating arm which causes the release bearing to move off centre as it is operated and the pivot points, as they wear, also allow it to drop down onto the input shaft. I have a idea that MMC have changed this design since I got mine though, so others may work better.

I then copied Bill's use of a concentric slave, using a Ford unit (in place of his SAAB one) and a home made alloy mount rather than the Burton Power ones. The biggest difficulty I had was getting an angled connection to the bleeding orifice on the slave. It sounds like Daniel has found a solution to that one though?

This system has worked well for me. It gives a nice positive feel clutch, not too fierce. And bleeding is just so simple....!

However I will admit to a problem with a notchy feel to 2nd gear which I haven't pinned down yet. It could be clutch not disengaging enough, but I don't think so. I think it is a gearbox problem despite having fully rebuilt this recently.

Guy
Guy Weller

Guy The slave you used was it of a fiesta.also have you still got the mesurment of the mounting or any photos. I am still using the old fork setup and is working ok but over winter will change to the concentric setup. thanks bas.
Barry

Yes Barry, it was a fiesta one, but the same unit is also sold for Puma and for Mondeos. Bought it off e-bay for £29. I think Ford list price is about £65

I machined a mount from a solid block of ally. 105mm diameter and 68mm thick. I cut the "nose" off the front gearbox cover and recessed the rear of my spacer so that it will seat securely over the front cover plate (which holds the input shaft oil seal) I used long bolts through the mount and front cover plate.

The thickness of the mount may depend on which cover plate you are using. The concentric release bearing "rides" the clutch continuously, but it is designed to do so. The travel on mine is about 12mm which seems OK. This is a dependant on the amount of fluid moved at the standard Spridget MC by a single pedal stroke, and the design of the slave. I couldn't find any data on either of these so I just put it together to see. I rigged up a temp line to the gearbox when out of the car and measured the actual movement on the bench.

Guy
Guy Weller

Most AP clutches have a recommended max travel of 9mm. The Burton co-ax (AKA concentric) slave sees 10mm of travel on my car for a full clutch stroke. I'm deducting 1mm for push back on release so aren't over stroking the cover, just.

I was prepared to make an adjustble master push rod to reduce the stroke if it was too much and may do this one day anyway (and one for the brake master too but to extend it).

An alternative method to prevent overstroking is to fit a clutch pedal stop on the floor or simply weld a blob to the back of the clutch pedal at the point it contacts the floor - 12mm becomes 11 or 10 or 9.

It's Ok for the bearing to ride the fingers continously.
Daniel Thirteen-Twelve

Guy Daniel. Thanks for the reply. I will collect the parts then do it later ,unless i have problems with the setup ive got. But it seems to work fine so far. ps best mod ive done would not go back to 4 speed .
Barry

This is my modified to fit the SAAB concentric Burton adapter (it cost me a fiver to get the alloy welding put on to allow drilling and tapping) which cost me a fiver on evilbay

The next shot will show the distance piece I made from Alloy billet (£8.00 at the metal stockholders) to adjust the fitment location.

There is a groove cut into it to allow the ridge around the back of the slave which secures its location securely and matches the groove on the front of Burton's fitment.


Bill

When I fitted this to the engine gearbox compination I found the clutch was squeezed "in" and I needed to reduce the block dimension several times until I had a "neutral pedal" setting

The finished block dims were approximately 0.650" in depth and when I do actually take it all apart there is a little more going to come off the block to get me a slightyly easier pedal.

mine is not quite as well equipped as Guy's I feel as the clutch is a little bit "on - off" and needs some pedal sensitivity adding in


Bill

Right now i see said the blind man. The so called burton adapter is to replace the front cover on the gearbox or you go guys way and machine your own to fit with an adapter to make the correct travel of the slave.I once had a master cilinder set up to pump the hydrolastic on the 1100 this would have been a good way to test the slave with the gearbox on the bench.
Barry

Burton sell adapter blocks so that one can adjust the set position of whchever slave set up you choose to use, all sorts of various thicknesses available

see here!

http://tinyurl.com/6g4od3

Me? I'm just too mean/cheap/poor to pay for something I can make

Add up a few of the prices to see what I mean!

And I love the "working in the workshop" aspect of this stuff, takes me back a few years.
Bill

and the part number of the hyd clutch unit please. Can see my engine coming out next weekend!


Alex Sturgeon

What type 9 is the best to get i.e from what car, Sierra 1800/2000 etc and any difference in years etc.

Think its about time i started to get the bits sorted.

Richard.
richard boobier

I get my bits for SAABs here

http://www.partsforsaabs.com/default.php?cPath=86_89

But if its for a K series I'd check with Arie De Best first, he started to do this then went back to cable for his K having issues with bearing movement IIRC

That IS a K isnt it Alex

My SAAB bits cost £35.70 for the slave and £13.99 for the bearing at present prices £50s-ish!

I didnt use genuine SAAB stuff, pattern was good enough for me

Part numbers: PFS901723 & PFS901767

But remember Burton kit needs modding to fit the SAAB bits but Ford stuff can be cheaper on eBay, and it bolts straight in!

Ask Guy!
Bill

I turn to Guy for type 9 advice sorry Richard.
Bill

If for an A series yes a 1800/2000 box is the one.

Yes Bill have a K fitted, must ask Arie how his is going
Alex Sturgeon

hmmm, what happened to my thread!!!!
I was asking about recommendation's for a new gearbox for my Midget!
Mallorcaben

Mallorca,

Is it by any chance only your first gear that it going out. The first gear in the original box does not take kindly to high speed and hard work. In my opinion, it was only intended to get the car moving enough to get into second gear.

The other thing they don't like is a fast shift from first to second with no pause in neutral. This tends to knock out the second gear syncro cluster. The same is true for all other gears for that matter, but to a lesser extent.

So, if your failures have been first gear, or the second gear syncro cluster, you may be okay repairing your stock box if you give it some velvet glove treatment.

I've never none a 5-speed conversion, but the two I have heard most about are the Datsun 210 (not B210) and the Ford Sierra. I think the Sierra is also known as the Ford 9, but others will know better.

If the advice is useless, at least it may help get your thread back.

Charley
C R Huff

Ben,

If you can get your hands on a Datsun tranny buy it. They are rare but even the Ford option is reasonable. They are found in large quantity and the only downside is you have to cut your crossmember as opposed to the Datsun tranny.

Bas
Bas Timmermans

Ive lost 2nd gear as well as 3rd now so I really need to do something quick!
Ive been told that the torque of my engine is probably too much for a standard box, but the 5 speed is around a grand, plus sending it to me in Mallorca, plus fitting here in a garage is 600€
help!
Mallorcaben

as always it's about cost I suppose; the Ford or Datsun conversions are available as kits, other boxes are possible if you engineer it yourself (Celica?). An A series SCCR will set you back a grand fitted too so the only cheap option is to stick with the standard box. The Midget Challenge racers in class B also have around 100bhp and they have to use the standard box and get a couple of seasons out of them so it's not out of the question.
David Smith

Have the gears stripped, or is it possible that you have shift fork trouble that is not allowing the gears to be selected?

I think that unless you run up on a special deal, David is right that the least expensive option is to rebuild your box or get a used one.

Charley
C R Huff

This thread was discussed between 05/07/2008 and 09/07/2008

MG Midget and Sprite Technical index

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