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Noise from drivetrain

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TRnorwegian

TRnorwegian

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I have aired this noise problem previously under different headings, since suspecting it could be coming from specific sources. I'm now not really sure.

It started 50 miles back, when accellerating hard in 1st. gear. A scraping, whining metallic noise seemingly from somewhere near the transmission (but not grinding like marbles in a coffee jar). Lately it occurs in every gear whenever the drivetrain is under load.

It does not occur when shifting. Shifting is no problem, and also as long as I keep the clutch pedal to the bottom the noise is not present.
To make the noise appear only aquires pressing the throttle a tiny bit more when peddling along on a flat road, whatever gear I'm in. When I let off the accellerator the noise stops.

So far, it has been suggested to derive from:

The transmission, caused by defect thrust washer, lock plate or other internals.
The differentiental, caused by one or two teeth missing in the crown and pinion assembly.
The engine moving and rocking into radiator hoses or other parts, transmitting the noise further back.

I plan to drain the oil in the transmission on thursday, hoping this may supply further clues. I also have an british vintage expert take it for a spin, and harvest his reactions.

If the transmission is the culprit, has anyone published a tread describing some step by step repair? Which kit is recommendable when splitting the transmission? Other part I should exchange when the transmission is pulled out anyway?

Thanks, Anders
 
Try to drain the trans fluid through a filter. A paper towel can work if needed. The idea is to trap any metal particles that you can. The type of metal can lead to a better diagnosis of what is happening inside the trans.
 
This symptom: noise under acceleration, quiet under deceleration, is suggestive of a differential problem. This symptom can happen when the pinion shaft has become able to move back and forth. Acceleration forces the pinion out into the diff. grinding against the rotating diff. carrier. Deceleration forces the pinion back into its bearing -- no noise.

I had this problem in a non-British vehicle, but all differentials have these parts in common. You should, at least, look for metal shreds in the diff oil too.
 
If it also happens in 4th gear, I think that makes it less likely to be a transmission problem. In 4th, the input shaft is coupled directly to the output shaft; no power is transmitted through the countershaft (meaning almost no force is applied to it).

Personally, I would proceed directly to draining oil and looking for sparklies. If something inside is screeching like that, it is destroying not only itself but likely the housing it lives in. Continuing to drive it like that may make the difference between rebuildable core, and scrap metal. Of course it may already be at that point, but I wouldn't risk it. Having the drivetrain lock up suddenly while you're at speed can be an unpleasant experience, too.
 
Aloha Anders,
I bought a bad overdrive trans to get a J-mainshaft. On dismantling, it was apparent the rear countershaft bearing had failed dramatically, allowing the back of the laygear/countershaft to move around. Under load, the back of the laygear was torquing to the right (viewed from the rear). The countershaft itself was worn where the hardened laygear had rubbed against it after the rear C-S needle bearing had come apart.

If that's your problem, look for metal shavings - hopefully you won't find any needles from the rear bearing! Like Randall said, in 4th gear the input & output are coupled, so the laygear is not under a load. That should help you diagnose, but sounds like you'll be pulling the trans.

Jeff
3xTR6
 
Have you checked the differential mounts? It could be coming from a broken mount, and the diff is twisting under torque.
 
TR3driver said:
If it also happens in 4th gear, I think that makes it less likely to be a transmission problem. In 4th, the input shaft is coupled directly to the output shaft; no power is transmitted through the countershaft (meaning almost no force is applied to it).
Click to expand...

I drove it this afternoon just to test the 4th. gear, and as far as I can tell, the noise is not there in the 4th. Does this suggest the problem is the transmission rather than the differentiental?
This being said (no noise in 4th.), the problem started in 1st. gear, and has moved it's way through 2nd. and 3rd. as it has increased. Perhaps it just hasn't hit the 4th. yet? And I cannot be 100% sure it's not there in 4th, since wind/ road noise in 4th. gear would mask the noise I was listening for. On the other side, I suspect I would detect the noise even in high speed and 4th. gear.

How unfortunate is it moving the car in this condition?
 
Anders,

Pull the trans. cover so that you can hear the transmisson better. Take a friend equipted with a length of garden hose. Have him focus one end of the hose at various places along the length of the trans. while listening at the other end of the hose. This will help locate where the noise is the loudest. If nothing stands out (there will be noises that you've never heard but are normal), look to the differential.

Differential: You might try putting the car on jack stands or just jacking the rear end high enough to get the rear tires off the floor. BLOCK the front wheels. BE CAREFUL, THIS IS DANGERIOUS! Start the engine and run through the gears, or just the one which is the loudest, while loading the differential by applying the brakes. Use the hose to listen to the differential (tie it to a stick so it can be held to the diff without getting under the car.

This may tell you where the problem lies. Hope so anyway.

Jim
 
bgbassplyr said:
Anders,

Pull the trans. cover so that you can hear the transmisson better. Take a friend equipted with a length of garden hose. Have him focus one end of the hose at various places along the length of the trans. while listening at the other end of the hose. This will help locate where the noise is the loudest. If nothing stands out (there will be noises that you've never heard but are normal), look to the differential.

Differential: You might try putting the car on jack stands or just jacking the rear end high enough to get the rear tires off the floor. BLOCK the front wheels. BE CAREFUL, THIS IS DANGERIOUS! Start the engine and run through the gears, or just the one which is the loudest, while loading the differential by applying the brakes. Use the hose to listen to the differential (tie it to a stick so it can be held to the diff without getting under the car.

This may tell you where the problem lies. Hope so anyway.

Jim
Click to expand...

It seems you have some experience to build on in problemsearching, Jim. I agree also with regards to being dangerous. Next would be having my friend lying under the car on my garage trolley, listening while road testing the car in high speeds :smile:

According to Pete Cox in UK (expert and Moss employee) the symptoms points very much in the direction of a problem with the layshaft or its bearing .

I've located a solid workshop with expertise on british vintage drivetrains. Sadly, it's abroad, in Sweden, but at least he's willing to make it happen in a month or so.
Since I'm not too pleased with my clutch, perhaps I should prepare for adjustments there since the tranny is out anyway? I find the clutch too hard for pleasant driving (even though I'm 90 kg and reasonably fit) and somewhat sticky. The pedal does not return/ follow the foot back smoothly, but in small hesitating steps. Probably too much resistance somewhere.

I've been told that Nelson or someone else at Buckeye has described a clutch set-up which was found to be almost too soft, but I'd rather go for that than the opposite. Not able to find the article however.

Anders
from Oslo, where good help is hard to find.
 
Driving down to Gothenburg this week, to have the transmission overhauled by the acclaimed best TR-transmission man in Scandinavia. Update follows when he split the trans.

Anders
 
Good luck with transmission overhaul, make sure all the alignment pins are in place before you install the transmission. The pedal not returning smoothly sounds like binding on the shaft.
 
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