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Throw Out Bearing Noise (?)

I am restoring a 1942 Chevrolet truck. The original engine was replaced with a direct swap 261 – a 1962. When the engine was rebuilt, I put the old clutch, pressure plate and throw out bearing behind it. The whole unit dropped into place without a hitch.

The engine was a bit noisy until I got the lifters set up now it runs well.

The problem I have now is when the clutch is depressed it sounds like a bad bearing.

I have replaced the throw out bearing twice in the past 3 days. The first one made no difference, so I asked a mechanic friend about this. His reply was that it was not uncommon to get a bad one – so I swapped it again. The same noise when the clutch is depressed.

I have the transmission out now – the shafts all feel OK, little wear on the input shaft. The clutch fingers are all flat, and everything seems bolted up how it is supposed to be. The bushing in the back of the crankshaft is OK. But it still growls when the clutch is depressed.

Does anybody have any idea what the problem is, and how to fix it?

Thanks,


Stewart

Stewart,

Interesting. I sure don't know what is going on. If your clutch is adjusted properly, and fully breaks the connection between engine and transmission, then it sure sounds like it IS the throwout bearing making the noise.

I'm not a believer in the 'bad off the shelf' philosophy. I haven't replaced gobs of throwout bearings, but have never found a new one that was bad.

You have replaced two, and still have the same problem. The only other thing that comes to mind would be clutch fork rubbing on something, but that's a stretch.

If for some reason it is a throwout bearing, you should be able to depress the clutch pedal only enough to take the free play out, and the bearing should start to growl. Keep us posted on the head scratcher.

Stuart

It,s possible you have a miss-matched TO. brg. There are 2 different diapram clutches Chev used. The old style had the fingers near parralel to the flywheel & set back in the pressure plate. It used a long TO. brg.It has about an in. collor. The newer style the fingers protrude forward almost out of the pressure plate. This used a short TO. brg. The groove for the fork is right behind the brg. If these are missmatched it could cause the problem. I take it your pilot brg. or bush. is good.

Gents,

Thanks for your replies.

I am not a fan of the 'bad from the box' excuse either. The bearing makers put lots of time and effort into making sure that the parts are right the first time. The second new bearing did not seem to make a difference, so I took the oldest one ( came with the the transmission in the truck ) to the transmission shop, and the fellow there said that it was fine.

I have seen the 2 styles of clutch fingers. I have the earlier style that is just about flat. The TO bearing is the standard part from 1938-1966. the pressure plate fingers appear undamaged, the pilot bushing is new also.

How much out of alignment can the engine to the transmission tolerate? I am not sure how this dimension would be upset - can it be a factor when a 1942 transmission is mated to a newer engine?

I was hoping to go for a drive, but this is starting to bug me.

Thanks again.


Stewart

Stewart,

Everything screams throwout bearing, but your math says otherwise. If the engine is relatively new, and so is the throwout bearing, one would be inclined to look at the '42 transmission as the noisy culprit. This might be true, but it would certainly make noise when the clutch was engaged and the guts and bearings of the transmission were spinning...not when it 'wasn't' spinning, as in clutch released.

As creepy as it sounds, I would be inclined to stick the truck up on jack stands, pull the gravel pan and watch and listen (a hose or stethoscope) while the truck ran, and someone did the clutch drill.

The problem is the reverse of what would be expected in a normal failure. Maybe someone will pop in with a "been there, done that" solution.

Could any clutch linkage be hitting a tailpipe or something else when depressed that gives you the false impression it's the bearing.

Stuart

Stuart,

The truck requires a lot of taking apart to get it drivebale again. I have taken it apart so that I can verify the issue that may have overlooked the engine rebuilder and assembler.

The manual shows a check of alignment between engine and transmission. I will need to tear off the pressure plate to access the pilot bushing to get a dial gauge into the opening to check this out.

Has anyone else ever had to fiddle with a old clutch cover/motor mount when swapping a newer 6 into an older truck? I read the Patrick's recommendations and can't recall this being an issue. ( I am really afraid that it might be, and that I will have to pull the engine out to nake it right!).

The clutch linkage and muffler are well away from the problem. the vehicle is right hand drive so the fork sticks in from the right side. the exhaust is where is 'should be' on the left.

I think that the transmission is OK - as you suggest it would be howling when driven - and my problem is when disengaged.

Best regards,


Stewart

I had a similar problem with my clutch assembly on my 1949 with a 261 over a 3 speed. As mentioned, two different throwout bearings but also differing clutch discs and the height of the disc hub. Gave me a ****load of problems until I got the right disc from NAPA. I documented some details on webshots in the album about the clutch. Never got the growl you mentioned but did find that the disc I got from a rebuilder was marked wrong between what was really the flywheel side as there was a distinct difference in the disc hub height. At least for my application.

http://community.webshots.com/user/geezer

Check your crankshaft endplay. If it's a fresh rebuild, it may be too loose.
Scott

Scott,

A couple of folks have suggested that the crankshaft endplay might be excessive. As the clutch disc and pressure plate look Ok, and the transmission seem to be all right, I am going to screw everything back together and address the endplay issue.

How does one verify crankshaft whilst the 261 is in the truck? If excessive, how does this get corrected?

Thanks,


Stewart

You can pry between the engine & flywheel & engine & damper. About 3-5 thousands is normal.

Alignment between engine & trans. are critical but it would cause a chatter problem on engaugment not likely what you are talking about. I,m thinking like the old Geezer. Something hitting the center of the clutch disc.

Boy! It would have to make a ton of noise before I would go to all this trouble. I would be tempted to just carry an extra TO bearing and wear a set of ear muffs. Then if and when something around the clutch came unglued I would know where to target my repair. That's, of course assuming the trouble is with the clutch etc.

Gents,

Thanks for the input - I appreciate your thoughts.

I have pried away at teh crank and seen 3/1000" free play maximum. No scrapping noise when running either. The clutch disc has no shiney bolt heads to indictae that parts are hitting other parts.

A couple of other smart guys have said to screw it all back together and let it work itself out. "It will wear itself in, or wear itself out."

And you are quite correct - I will know where to look when something bad happens, heck, I nearly have my apprenticeship done in swapping TO bearings now!

When I have a few more miles on the truck I will report back to let you folks know if it got better, or if it got worse.

Best regards,


Stewart

I've got a similar problem on my "new build." I just posted the following in an old thread but will follow-up here as this thread is fairly current:

If the source of the noise in Stewart's drive train has been rectified I would be very interested to know what was found.

Thanks,

Don

Don, and other Stovebolters,

I have been off the web for a while - I guess my motherboard was bored and ready for retirement. I think I am mostly back on line now.

I took the whole drive assembly apart and gave it a good visual inspection. Everthing looked good, so I cleaned everything again. I applied antiseize to the input shaft splines, and a bit of sealer to the thru holes in the gear case.

I bolted everthing up where it was supposed to, filled up the crashbox with oil, lubed the shifter and put all of the floorboards back in place. Then I started the new 261 up and now hear a bit of a reduction in noise - but not much.

The throw out bearing rattles more that grinds - and only when it is spinning ( sort of like when it hurts only when you breath ...), but it drives the truck OK. I have few miles on the old truck and hope to get in a few more prior to the snow.

I know that it will get better - I will report back when I get some more miles on the clock and see if it wears in, or wears out.

Best regards, and good luck with your TO bearing.


Stewart

Stewart -- Inspected mine this morning on a lift. We removed the gravel pan started the engine, depressed clutch, inspect, depress, bs, depress, listen, depress and look closer. Everything actually seems in place as it should be. We think, just maybe think, that there is something going on between the pressure plate fingers and throwout bearing. After adjusting the linkage freeplay as much as possible the noise has abated about 50% or so.

At this point I'm going to drive it some more and will then put it up on jack stands in my garage and remove the clutch assembly for inspection. I've going to keep in mind that the last time I put Viejo, my truck, up on jack stands it set there for 12 years!

Will keep you advised of any new developments.

Don

Bump to top of "Active List"

Also, see my recent post concerning this on-going problem. HELP!
Rattle rattle rattle - it's embarassing to drive

Don

I didn't see any mention of the pilot bushing/bearing. When you had the transmission out, did you look for the pilot bushing? Rebuilt engines often don't include that bushing. If it is missing, the clutch shaft doesn't have proper support on the crankshaft end and can wobble as it rotates. That can upset the throwout bearing and cause noise even though there is nothing wrong with the bearing itself. Try putting the transmission in gear when you hear this noise, but hold the clutch- if the sound changes, I would suspect the pilot bushing is worn or missing. Some Chevrolet and GMC engines used a ball bearing in place of the oilite bushing, but they are interchangable, and the bushing was standard for decades.

As for transmission and engine alignment, typically you had to disassemble the transmission and bolt the case to the bell housing. I don't remember the procedure, but factory shop manuals describe it. Generally that alignment was not a problem unless there was severe wear on the bell housing or the transmission case. Case misalignment also will cause the transmission to jump out of gear when driving.

Harvester

I think I spoke incorrectly about pilot bushings and bearings being interchangable. I don't think they are, after having thought about it.

Harvester

Here is a thought. When you have the clutch in and it is in meutral, there are shafts turning in the transmission. If you have it in gear with the clutch in, there are no transmission shafts turning. Are there any sound differences between these two cases?

The noise is essentially the same regardless of whether or not the transmission is engaged or in neutral.

The engine is in the shop right now but I will definitely be checking the pilot bushing situation when I pick it up next week.

Thanks for the input.

Don

im having the same problem my clutch is only a year old only i never adjusted the free play so the clutch was tight no free play so the bearing started clnging and rattling i ajusted it but to late damage had been done as soon as it warms up i will put a new bearing in learned a lesson if you have a clutch make sure you keep some free play in the linkage or the bearing will be spining all the time instead of just when depressed

Hello,

After a long vacation I am happy to report that after 35 miles the throw out bearing nosie is just a tiny rattle when the clutch pedal gets pushed in.

The truck runs along the road OK (at the top speed of 40 MPH)and you have to listen for the rattle to hear it. The little noise it does make is not dependant on temperature, so I hoping that it will go away completly after a few more miles.

Thanks,


Stewart