fault finding Drive chain

[flyer295]

I've at last got the engine running and all appears to be well until I reversed it out of the garage.

 

Symptoms :-

 

With engine running and reverse gear engaged the car moving backward slowly down a slight slope if I disengage the clutch the car rocks to a stop just as if the engine had been switched off with the car in gear. I tried in forward gear and it has the same affect. With the car stopped and the engine running and the clutch disengaged it is extremely hard to get it out of gear.

 

I have jacked it up and repeated the process ( both wheels off the ground) and all appears normal. If I engage 2nd or 3rd the whole back end of the car shakes violently in what appears to be a vertical plane, probably against the rubber mountings.

 

With the wheels in the air both wheels can be turned freely by hand.

 

Some time ago I tried a static test with the rear axle disconnected and at the time it appeared to be ok.

 

My thoughts are that it could be :-

 

a) The prop shaft severely out of balance although nothing is obvious

The rear axle has a problem internally, a replacement unit fitted of unknown history. Sold as good !

c) A problem inside the gearbox/overdrive. I re-built it and everything appeared to work prior to fitting.

d) A clutch problem. All new. Doesn't grind when engaging and drive to the engine stops when disengaged. As it all should

e) A u/j problem, if so which one.

f) Something else

 

Has anyone ever had this problem and CAN ANYBODY HELP ?

 

Bob

[Peter Cobbold]

Bob,

Could it be the overdrive actuated/engaged? Can do lots of damage driving it backward when engaged.

Check or disconnect the o'd loom?

 

The difficulty in getting it out of gear with engine running and clutch pedal depressed sounds like typical 'spinning plate' - the clutch driven plate is not releasing from the flywheel. Either because not enough motion applied to the fingers, or it has rusted on. But not sure how you could do that with the car stopped, it would have to move if the engine runs and its in gear.

 

Wait for more replies before restarting it. Another possibility is two gears engaged at once?

 

Peter

[flyer295]

Peter,

 

I don't see how 2 gears can be engaged at the same time. After rebuilding the box all seemed to be ok when it was turned by hand. There doesn't seem to be any problem while up on jacks, at least not in 1st or reverse but the shaking at higher speeds in 2nd and 3rd is tremendous. I'm not so sure about the o/d. I did put new bearings in it and the clutches in the o/d were freed.

 

1st & reverse, are the only gears I've tried. This jamming or locking up appears to only happen under load (with wheels on the road), which makes me think it could be something to do with the diff. If there was would that cause the shaking? I suppose it could if head bearing in the diff was worn and out of line. No play was detected before fitting the diff but I've assumed that it was all ok and I didn't strip it at all.

 

Bob

[Peter Cobbold]

Peter,

 

I don't see how 2 gears can be engaged at the same time. After rebuilding the box all seemed to be ok when it was turned by hand. There doesn't seem to be any problem while up on jacks, at least not in 1st or reverse but the shaking at higher speeds in 2nd and 3rd is tremendous. I'm not so sure about the o/d. I did put new bearings in it and the clutches in the o/d were freed.

 

1st & reverse, are the only gears I've tried. This jamming or locking up appears to only happen under load (with wheels on the road), which makes me think it could be something to do with the diff. If there was would that cause the shaking? I suppose it could if head bearing in the diff was worn and out of line. No play was detected before fitting the diff but I've assumed that it was all ok and I didn't strip it at all.

 

Bob

Bob,

Not two gears on the same fore-aft gate, but it is possible to have say 2 and 3 engaged together. I nearly did that when replacing a broken gear lever. The box was still in 3rd and I set the new lever up in neutral and nearly selected first...then remembered I'd read about getting two at once. But you rebuilt it all in neutral so forget this suggestion.

Did you pull the prop shaft apart - if so are the yokes correctly assembled not 90deg out?

Peter

[john.r.davies]

I suspect the hand brake.

As usual, forgive me for limited TR experience, but in small chassis Triumphs, if you jack up the rear axle, the suspension goes into full dropp and loosens on the hand brake cable. Put it back on its 'feet' and the cable tightens, so that 'correct' is then 'too tight'. TRs are different, I know.

 

Try putting it up with axle stands under the rear uprights, so that the suspension is in the normal position. Set the hand brake cable and it should still be correct when you put the wheels back on the ground.

 

John

[flyer295]

I've changed the prop shaft as I thought it might be that I had a 2nd one that I hadn't touched. Slightly better, no heavy vibration.

 

I've disconnected the handbrake lever ( had to do that to remove the gearbox cover) so the brake cables are slack - Still the same.

 

I've disconnected the wiring to the overdrive unit. - Still the same.

 

I've run the engine in gear without the prop shaft disconnected. Appears ok.

 

I've put the axle stands under the swinging arms to simulate cars weight on suspension and turned the wheels singly, together and in opposite directions. They run free as they should

 

I've put power through the drive train while the rear end is jacked up -- Appears to be ok.

 

ONLY WHEN I PUT DRIVE THROUGH THE WHEELS AND THEY ARE ON THE GROUND DO I GET THIS PROBLEM

 

If it's the diff, why does it work with no weight on the wheels?

 

I've run out of ideas. CAN ANYONE SUGGEST A SOLUTION ?

 

Bob

[Peter Cobbold]

Has the osf pressed steel diff hanger fractured? it leaves the diff supported on only three pins. Had that happen- loud clunks on taking up the drive.

Diff probably would not move unless torque applied through the wheels. Check also osf pin has nto pulled out of chassis.

Peter

Edited May 26, 2014 by Peter Cobbold

[flyer295]

Peter.

 

I haven't checked these recently but they should be ok as one was cracked when I had the chassis separate from the body and I put a new pin in and strengthened them. The car has not moved since then, at least not under power. This is the first time at trying to drive it after a complete rebuild.

 

When I ease the clutch up in gear there are no adverse noises. It's just that it will move a couple of feet then if the clutch is pushed down to ease the amount of drive so it will roll back or forward it will rock to a stop. I'm a bit reluctant to try and force it by keeping the power on.

The best description is it's just like stopping the car rolling by turning off the ignition with the car in gear.

 

Bob

[AlanT]

The classic fault-finding technique is to divide the area of uncertainty in half.

 

Remove the propshaft. Run the engine and use all gears, reverse, OD etc.

Push or tow the car about with the engine off.

 

Now you will know which has to be moving to make the vibration come.

[Peter Cobbold]

I think it is the diff, since Its OK running the engine and changing gear with the prop shaft removed. (#6).

The 2 feet of motion before locking up is a clue.

The circumference of a 15" tyre is about 1.7m = 5.5feet. So 2 feet is 'about' one third of that. Diff ratio is about 3.4 Theres the clue.

So measure that '2feet' accurately and see if the lock up occurs with one whole turn of the diff, or nearly so.

When you tested the diff with wheels off the ground did you try three to four turns of each road wheel?

Peter

[AlanT]

Does the diff still have the spilt-pin type thing in the vent-hole.

I've often wondered if these ever finish up inside.

 

Perhaps a 6 does not have a vent-hole?

[flyer295]

Peter,

 

My thoughts are the diff. I have not turned the wheels a whole revolution. I will do this in the morning.

 

It still worries me that there seems to be no problem with both wheels in the air. I suppose that if there was only a slight misalignment somewhere inside if not under load this might not be noticed, but whatever is causing should be noticeable only there is a lot of resistance required to stop a car.

 

What fault in a diff could cause this, worn bearings? I've never taken one apart before.

 

Bob

[AlanT]

With both wheels off the planets spin but the crown wheel does not move.

 

This is why spinning one wheel drives the other in the opposite direction.

[Graze]

With both wheels off the planets spin but the crown wheel does not move.

 

This is why spinning one wheel drives the other in the opposite direction.

Thanks Alan, I had noticed that but didn't understand why

 

Graze

[Peter Cobbold]

Bob,

Diagram: http://web.mit.edu/2.972/www/reports/differential/differential-1.gif

As Alan says wheels off the ground allows the wheels to turn the sun and planets, and the other shaft. but not the crown wheel. Unless the other wheel is on the ground, or braked stationary, the crown wheel doesnt turn. There's your test: lock one wheel to see how far you can turn the other

With wheels on the road the crown wheel can turn until something jams it - maybe a loose foreign object.

Peter

[stuart]

Probably a tooth off the crown wheel or pinion or both.

Stuart.

[flyer295]

Peter,

 

I've jacked up each side in turn and the raising one wheel at a time then rotated the wheel 4 or 5 turns in both directions. No problem !!!!

 

This is exasperating !!!!!!!!!!!!!!!!!!!

 

Could it be inside the gearbox or o/d unit. I did have a problem with the o/d. When I got the box the clutches were seized on the cone, I eventually freed them and re newed the bearings. As far as I know it all went back correctly. I am having a problem with the solenoid working, needs a new one I think. If solenoid not working would this create this problem? I wouldn't have thought so.

 

Bob

[littlejim]

"With engine running and reverse gear engaged the car moving backward slowly down a slight slope if I disengage the clutch the car rocks to a stop just as if the engine had been switched off with the car in gear. I tried in forward gear and it has the same affect. With the car stopped and the engine running and the clutch disengaged it is extremely hard to get it out of gear."

 

Does the first part of this make the experts reckon a good look at the brake shoe set up a la John R. suggestion? Sounds like something is not springing back into place when the brakes are released?

 

Part two would make me have another go at adjusting the clutch rod. After I fitted a new clutch plate (Moss) I had to wind the actuating rod way past the normal spot, and fit it to the top of the three holes in the actuating lever, before I could got it to stop dragging. (Adjustment of the clutch done with it up on axle stands with handbrake fully on.) I put it down to Moss providing more meat on the new clutch plate.

Edited May 27, 2014 by littlejim

[Peter Cobbold]

Bob,

The clutch, all gears and o'd work OK with prop shaft removed. And you've rebuilt them too. So I'd still focus on the diff. Its an unknown, and the bouncy motion came from the rear.

Your test means the crown wheel and pinion is turning fine - when the crown wheel turns the pinion. Normally its the other way round. It may be that the pinion is so worn, or its bearing, that when you apply drive from the prop shaft it rides forwards across the crown wheel and jams after a short while. You should - I imagine - see the flange move forward measurably when the propshaft powers the pinion.

Whats the end float on the pinion?

Peter

Edited May 27, 2014 by Peter Cobbold

[flyer295]

One of my next tests is the brakes. I intend winding them right off. Just put a wooden bar in the drive to act as a stop. Then try it. They do drag a bit at the moment, but you need that to maintain a 3 or 4 notch handbrake.

 

Are the gearboxes notorious stiff and difficult to select? this one is.

 

Bob

[flyer295]

Peter,

 

End float on the pinion. I understand what you mean but I'm not sure how to measure it. I have a DTI. can it be measured in situ. and how much should there be. There's no obvious visual lateral movement. What you say makes sense as when I try to drive and it hits resistance, if I disengage the clutch and try to repeat the maneuver it doesn't start with a stiffness, it just repeats the the problem. I measured the distance of travel before the resistance and it's 18" which is approx 1/4 of a turn of the wheel. and approx 1 complete rev of prop shaft.

 

Any of that make sense?

 

Bob

[Peter Cobbold]

Bob

A stiff or impossible gear change can be caused by a spinning plate clutch eg clutch hydraulics not disengaging fully, or driven plate rusted to flywheel. But you said with prop shaft off the clutch and gearbox works fine?? Is that with engine running and for all gears including reverse? a siezed on o/d wont like reverse, be careful.

If that all works OK then:

Look for something that changes when the prop shaft is engaged , the wheels on the road and the drive chain exerting torque. Maybe torque makes the bell housing move on the block causing the clutch issue? But it has to be something that allows 2 feet of motion then locks up. I dont see rear brakes doing that. If you can turn the wheels four times by hand with brakes loosened they are not going to affect the drive chain one jot.

The locking up occurs both forwards and backwards. That might eliminate the diff pinion too as I'd expect torque on that to pull it into mesh ( good) or out of mesh ( bad), depending upon direction.

So you are looking for something that is fine unloaded but locks up in response to torque applied in either direction, and allows 2 feet of travel between the two. Right? - does that fit the symptoms?

Peter

[Peter Cobbold]

Peter,

 

End float on the pinion. I understand what you mean but I'm not sure how to measure it. I have a DTI. can it be measured in situ. and how much should there be. There's no obvious visual lateral movement. What you say makes sense as when I try to drive and it hits resistance, if I disengage the clutch and try to repeat the maneuver it doesn't start with a stiffness, it just repeats the the problem. I measured the distance of travel before the resistance and it's 18" which is approx 1/4 of a turn of the wheel. and approx 1 complete rev of prop shaft.

 

Any of that make sense?

 

Bob

I think the end float will be obvious to the eye if you lever the flange against the housing nose, forwards and backwards with a long screwdriver.

Or measure flange to housing with a rule after 'locking' the drive, first forwards then backwards. Compare the two. I'm thinking quarter inch - really bad movement, nothing subtle. But you will have to apply drive torque to see it.

 

Can you clarify. Locking it up, then depressing the clutch frees the lock up and the car can be moved 18" again? Does that happen both forwards and backwards?

 

If the 18" distance doesn't change with the gear you're in, then its after the gearbox.

If the pinion is tight on the diff and the choise of gear makes no difference I think its pointing towards overdrive.

When you press the clutch to free the locking up do you hear any noise from the o/d ? (stethoscope or screwdriver to ear).

 

Maybe the od clutch mechansim is allowing 18" of motion before it locks? It doesn't lock when the prop shaft is off because there's no torque on the output shaft. But if you connect the prop shaft and apply torque by having wheels on the road, the od locks up. ????

 

Peter

Edited May 27, 2014 by Peter Cobbold

[AlanT]

When you were working on the OD did you remove the roller uni-clutch?

[flyer295]

Peter,

 

The 18" was only in 1st. I haven't measured it in reverse or any other gear.

 

Depressing the clutch does seem to free the lock up because I can repeat the process.

 

One thing I did notice this morning, only I didn't have time to pursue it, is with just very gentle engagement it appeared not to seize. I'll have to investigate this more tomorrow.

 

No end float obvious.

 

I am wondering about the gearbox as the selection of gears is very hard and I'm pretty sure it shouldn't be like that. With regard to the o/d unit. I overhauled it but never having seen the inside of one before it may be possible that I've assembled it wrong in someway.

 

It's a brand new clutch, flywheel skimmed. There is about 1.5 to 2" of travel on the clutch pedal after it goes past the point of activation so I would of thought it has plenty of travel to operate.

 

Is it possible that I could of put the top cover on the gearbox wrongly and somehow got the selectors out of kilter. When I had it out of the car I can't remember it being so stiff and I did temporarily remove the top while it was in the situ.

 

Bob