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Triumph TR6 - Differential diagnosis

Greetings,

After all the discussion about lurkers who don't have 'real' Triumphs I hesitate to pop up here ... no I don't.

I have a 73 GT6. Its saving grace is that it has a TR6 short block. Since I installed a 1/8 inch head gasket and got the compression ratio out of rocket fuel range it's been running pretty well. But, the diff is scaring me. It's not too bad going forward. But it seems a little crunchy in reverse. I realize that some of the noise is just normal idler gear rumble tranmitted though the drive train, but the audible clank when I shift to first is making me drive too slowly - sometimes.

Is there a simple test I can do to determine whether wear is excessive without opening the pumpkin? If I jack up one rear wheel I seem to have about a third of a wheel rotation of backlash. Oil level and universals are good.

thanks
Don
Don Gardner

Hi Don

Know nothing about GT6 rear. But in general the greater noise in reverse and clunk might be.

1:Wheel bearings shifting on torque? If they are very worn or damaged. Cheapest best check first if you haven't. Put her up on stands and spin wheels fore and back and listen. Put a bar under wheel and lift at angle for play. Jack up just enough to get bar under. This is more of a feel thing. Your looking for more in and out play. In the diff it could be the pinion bearings, axle etc. Gritty noise combined with clunk says a very worn bearing to me.

2: If you can drain the oil on that diff without opening. Drive till warm then drain and check oil for small metal bits. Half inch hole use a retrieve magnet and fish a bit. If theres a lot sorry. Various bearings make up the pinion and carrier so open it up and look.

Good luck
Bill
B Brayford

The bearings are new and seem to be ok. The major concern now is the clank when moving form coast to drive. Any body know a reliable way to check proper gear backlash from outside the differential?

Don
Don Gardner

Don,
'Clonks' from the transmission are more usually the universal joints than diff problems. Wave you a worn U/j? Lever the spider wth the wheels up.
John
JohnD

Good point John. Since were close to the axle a bad U/J will sound gritty as well.

I don't know of anyway to check play outside scientificaly. You may be able to isolate it by backing up on ramps and reefing back and forth on drive shaft in neutral. Block it real well and listen for clunk. A good pair of channel locks can move the car easy. Or jack up and set parking brake would work but splines etc. will not be in running angle. I will be at shop tomorrow and give mine a test since its sitting on the floor. Maybe I can give you a reference point.

How is that diff mounted anyway never been under one. Could the diff or rear suspension be moving around or shifting.

Bill
B Brayford

Hi Don

With both axle drives held my driveshaft input has an almost zero movement possible 1/16 fore and aft. Each axle side seems the same.

Good Luck
Bill
B Brayford

Don
I have a clunk in the rear end when starting from stop either forwards or backwards or slightly rolling and clutch let out. I climbed under her and held the inner yoke and shaft while friend turned the tyre back and forth. I had a lot of play and noise on driver side and less on passenger. There is no way it is the outer yoke splines so the only thing left is the u/j at both axle shafts. So guess what one of my projects is this winter?
Rick C
P.S. Bill B. and all other newbees to the TR lifestyle (the poor house:) Do you have: The Roadster Factory spare parts Catalogues..Volume one and two. Beleive me..you will find them very helpfull in a body off restore ( and you will have answered your question). 2 ways to get them: Go to TRF web site and request them to mail you a set..or ( In Canada) call Fred at British Auto Sport (1-888-485-2277) and tell him you are doing a body off and could he send you a set of them...his prices are not to bad for parts.
Rick C
Rick Crawford

Hey Rick C.

When I got my first TRF catalogue early 90s volume 2 had not been published. Mr. Runyan and crew sent Vol. 2 to me without asking hot off the press in 93. I agree they are the best for standard assembly.
Now unless yours are updated I can't find info in them for other than the standard re-inforcement of frame and body aka Kastner. Those I have done over the years on mine and for others. Plus a few I have deamed up on my own.
I have found a lot of sights though Dan Masters and chatted with many others who are going the extreme route. Everything from building there own custom frames the way I will likely go to cutting the whole works up the center and adding 11 inches to the width body and all. All are nice cars. Currently designing a frame jig.

Thanks
Bill



B Brayford

Ha Bill
Sorry but by your question (How is that diff mounted anyway never been under one), thought maybe the books might be helpfull...obviously u are way ahead of me:) Nope books have not changed.
Rick C
Rick Crawford

Hey Rick

Don Gs car is a 73 GT6 and I have never been under one. Lots of TR6 and too few 250s no GT6. Since Don has not reposted I still don't know.

Hey Don

Again I have never been under a GT6. Due to my own curiosity and Rick Cs comments:). I made a couple of calls and it came up the same as I asked originally. What rear end configuration do you have. At the end of the era GT6 Nov. 73 the car may have come with a number of rear end setups? Don't laugh a 91 VW Jetta has 3 possible brake setups alone, none are close to the other. Dodge 1/2 tons have three possible clutches take out measure and we will order.

Double wishbone is a hope as earlier etc. Bl was trying to get it right. All agree though a sharp audible clunk is likely diff and suspension mounting broken or worn out U/Js dry and worn, loose parts brakes etc. rather than internal diff parts. The gritty sound is another story apart from u/js. You've got to have a lot of internal movement for that EP oil at proper level to allow an internal clunk you can hear I would think. Can't advise further unless I know what you've got.

Steven and I agree TR250/5 mix if they spent the money getting that fuel injected TR5 certified in America we would all be out looking for C5 Vettes and picking up our performance parts from the BL dealer. 1968 TR250 owner 73-78. 1972 Tr6 owner 85 till death do us part?

Don if you are still there and interested let me know don't need #s just a description.

Bill
B Brayford

Thanks guys,

Lots of good stuff. I apologize, I was distracted by 'work'. I'll try not to let it happen again.

I have the first of the last GT6's KF20068U. The rear end is a diff case solidly mounted to the frame, a transverse spring bolted to the top of the case (just swapped this out a couple of weeks ago for butt dragging problems, all was/is tight), half shafts w/universals, and a forward link to the body. The half shafts run though bearings mounted in uprights that hang from each end of the spring. The forward links attach to the uprights near the bearings. If that's clear as mud, I think Spitbits.com has a pretty good diagram in the GT6 portion of their catalog.

I bought a basket case with a suspension like a shopping cart. The only time I drove it before I tore it apart, other drivers actually backed away from me when I pulled away from stop lights - scary. By the time it was back together this summer, all bolts, bearings, universals, rubber diff-mounting pads, assorted bushings, and brake parts were new. I couldn't tell that the spring was weak before I set the body back down - but, now that's new, too. The forward link mount points on the body were repaired and reinforced during body repair.

Initially all I knew was that I had a symphony of noises in the back end that I've been gradually eliminating. The old spring was missing a rubber interleave between a couple of layers and I rehung the exhaust from rubber so that the tub doesn't resonate at sympathetic frequencies. I still have the occasional clank from coast to drive and pronounced vibration over 50mph.

Based on you suggestions I will look at my bearings and
the points where drive train parts bolt together. If I can find a place that can do it, I'll have my new Minilites and Michelins rebalanced on the car. The drive shaft had a balancing plate welded on. I stripped the old paint during rebuild and tried to be careful to give it an even coat of new. I might have to have that rebalanced. But, first I think i'll look at the end flanges for a loose bolt or off center location.

Mostly, I think that the car just needed to be driven after years of idle neglect. Either it's getting better every week or I'm getting used to the chaos.

Don
Don Gardner

Hi Don

If the car sat in one spot not driven for years you can bet it will get better as you drive it. The diff gears will be rusty were they sat out of the oil. Oil runs off top of gears condensation takes over now you have rough surface clean surface for awhile.That would give that crunchy sound that will get better as the gears turn against each other. You have been driving it for awhile cleaning off that rusty grit and its floating around as the diff turns getting into open bearings and between gears. Change that oil.

If you don't want to take it apart. I have had success this way. Most Diffs. do not have a bottom drain. A Rodder trick is drill and tap one when its open. All I have seen have a side filler plug set at the full level halfway up. Take the diff out ONLY turn on side and drain probably 30 year old orange rusty mollasses. Wear rubber gloves it stinks and is acidic. Do about 3 washes with varsol. Couple of gallons Use an oil suction gun cheap 10 bucks if you don't have one. DO NOT TURN IT TOTALLY UPSIDE DOWN. Just wash back and forth most crap on bottom and you want it there or out the drain. I use an old shop vac to make sure I get the last of the varsol and crap at the end. Turn the shafts a few times and feel and listen you will have a better chance of hearing and feeling wear and damage backlash etc. without the oil. Refill with recomended oil.

The clunk from coast to power.
Just from pictures on the mounting setup.
While the diff is out check what looks to be front pins for diff on chassis. I don't know how they are in there but reef on them passenger side especialy were the torque exerts. It looks a lot stronger than TR6 but check. Make sure the rear rubber bushings are in good shape and the bolt holes in frame aren't oval.

Check those funny little brake drum screws if missing will cause clunk. Brake hardware shifting etc.

Vibration
I doubt cleaning and repainting your drive shaft would throw it out of balance. Unless you were playing baseball with it. Sounds more like phasing to me. But get a good alignment and wheel balance first. If any of you other guys know a better way please post this is real time consuming.

When you replaced the u/js did you mark everything drive shaft u/j and collar to keep them in relevant phase. Some have a factory mark some don't. Look for factory marks tranny collar. Drive shaft collar and drive shaft. On an irs car that applies to halfshafts as well. Is your half shaft spline keyed. I thought they all were but I have been told different. Unfortunately if no factory marks and the the last guy who changed them didn't pay attention your marks won't matter.
Mark shaft and yoke Take U/J out at tranny turn 180 deg. and road test. If no better or worse leave it. Worse change back hopfully perfect your done otherwise go on to halfshafts. Driveshaft turns at higher speed and would be most likely. Those words going through your head about now would make Mother wash your mouth with soap :). Been there didn't dun that then dun dun dun that know the words.

Don writing this I keep coming back to a bad U/J bearing. Maybe new but those little rollers can be tricky. One screwed up one will give all your symptoms gritty and clunk and vibration. I would double check them first.

Thats about all I can think of. Don't know what all applies in your case. Would change that oil though diffs aren't cheap.

Let us know how it works out.
Bill
B Brayford

Thanks Bill,

This all might take a couple weeks as I hate to be without the beast now that it's starting to like me. Drove it in the first really cool weather we've had here today - never run better. Better'n sex (don't tell my wife).

Don
Don Gardner

Bill,
All done from the diagrams; I'm impressed!
GT6 prop shaft (aka Transmission shaft?) end flange bolt holes are symmtrical in only one plane, so they can go together two ways. With both front and back, that's four possible permutations. If no marks made (never seen a factory mark) then try the rear flange the other way, then reverse the front flange. And make sure the whole shaft is not back to front!

If all else fails, two jubilee clips around the shaft, with the nuts on opposite sides to balance, then move one clip around the shaft and test drive. If vibration worse, move it the other way, but only slightly each time, until the vibration lessens. When minimum, try moving the other clip in the same way.

Time consuming, but at least you get to drive your car a lot!
John
JohnD

Hi John D.
Thank you so very much. First three sentences I bow to a pro.

Don G.
Print and follow this JohnD post. Gentleman probably has a couple of gigabytes of knowledge on the subject.

Bill
B Brayford

To all who've helped, thank you.

I think I found the problem.

Being kind of a 'direct approach' kind of guy and not too mindful of my safety, I jacked up one wheel, put it in second gear, hauled back the choke, fired it up and crawled underneath to see what was going on. The whole back end was gyrating like a hula dancer and it didn't take me long to see why: the back end of the prop shaft appeared to be bent at about 5 degrees - swinging in a circle about 1/2 an inch too wide.

I crawled back out from under, put out the tailpipe fire on my shirt front and consulted the manual. There in tiny print as big as a billboard were the words "Note: Do not disassemble the sliding joint for any reason". Reflecting first on all the other inexplicable things the DPO had done to this car - and secondly on the high state of engineering accuracy for which these cars are so famous, I deduced the following:

The male splined portion of the sliding joint was welded to the end of the prop shaft pipe by hand. I'm sure they used a jig of some sort. But, welding is hot work and after a Guinness or two it was all kind of theoretical. The borehole in the female casting was likewise approximate. But, they had a solution. You just pick random male and female bits from the bins and try them out together until you find two that when fitted together 'just so' form a straight line. Hence, the injunction against ever taking them apart again: such serendipity is seldom repeatable.

Knowing my DPO as well as I do by now, I indexed the tailpiece around 180 degrees and miracle! the vibration disappeared. I'll try fine tuning, a spline at a time, until I find perfect. But, the drive to work today was a revelation. It seems that the forces exerted by the out-of-line shaft were setting up all kinds of other harmonic vibrations and lateral stresses on the differential mounts that made it feel as though the diff was going to explode. The input bearing on the diff seems to be OK - I can't detect any side play and it's not leaking any more than all the other joints in the drive train.

Thanks again and, yeah it stands for D*mned.

Don
Don Gardner

I read once that no-one was able to resolve a similar problem either at home, or at the expert garage he went to. Eventually he found the solution. The inside of the drive shaft had developed rust during a long period of non-use and when he drove the beast, the d/shaft was out of balance where metal was missing and all this scaly rust moving around inside was making it even worse.

You have to get to know the gremlins in your car better than you think - if you ever hope to defeat them.

Don Elliott, 1958 TR3A
Don Elliott

This thread was discussed between 24/09/2002 and 07/10/2002

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