Strange Noise

[Stewart Loy]

Throw Out Bearing Noise

I am restoring a 1942 Chevrolet CMP GS 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

[charlie fitton]

pilot bearing?

[Phil Waterman]

Hi Stewart

Charlie Fitton may have hit the problem right on the nose with the pilot bearing several different types used from roller to bronze bushings which can and do make noise. What condition is the bearing surface on the transmission piloted shaft?

From your posting it is unclear if the noise goes away when the truck is in gear and moving?
Also when the clutch is pushed in is it trying to spin the transmission?
Is the sound the same with the truck transmission in gear with the clutch disengaged as it is when the truck transmission is in neutral? Reason for these questions is to rule out a miss alignment of the transmission to the engine. When you did the engine swap did you check the centering of the crankshaft to the mounting hole for the transmission (see manual for details). I had to replace a broken bell housing and was surprised how much out of alignment the new bell housing was.

Also does the noise change between the point where the clutch has just released and all the down on the peddle? If so check peddle adjustment to see if the clutch is being pushed two far in.

Is there any indication of clutch slippage?

[Alex Blair (RIP)]

Originally posted by Stewart Loy
Throw Out Bearing Noise

I am restoring a 1942 Chevrolet CMP GS 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

Stew....

The pressure plate actuation fingers of a friction clutch are provided with means for noise attenuation by the application of acoustical materials, alteration of the mass of vibrating parts, or surface treatment of slipping parts either individually or collectively to prevent the generation of objectionable noise due to resonance and sympathetic vibrations that are initiated by the stick-slip phenomenon as the non-rotating clutch release bearing contacts the relatively rotating actuation fingers.


Those "Clutch fingers " as you call them are actually Pressure plate fingers and it sounds like "rust'..take a real close look for broken springs in the clutch disc and that the fiber is not separating from the plate..
Then give your pressure plate a good bath in the parts washer and blow it clean with air hose and clean dry it with a shot of brake cleaner..(Not the clutch disc)..but a shot of brake cleaner on it would dry out any oil on it and not damage it.

make sure there are no burrs or dings where your throw out bearing slides and it is travelling the full length..
Sounds like a throw out bearing still..but a spare throw out bearing wouldn't be out of order.
If you hear the noise when you push on the clutch pedal, it could be a faulty release bearing. This problem needs to be repaired before more serious damage occurs.
If you hear the noise when your foot is off the clutch and pushing the clutch in makes the noise stop, this probably a problem with the input shaft bearing in the transmission

Keep us informed.

[peter simundson]

.........It might be the driver........Tee hee.

[Lynn Eades]

Not trying to insult you Stewart, and not being familiar with what your working on, Here are a few basics
Is the clutch plate installed around the right way?
Is any part of the clutch hub fouling the fly wheel?
Have you a problem with engine thrust bearings/ crank endfloat?
Is the back of your flywheel rubbing on something when the crank is pushed foward(A too long bolt, or a dent in the clutch cover)
This may be irrelevent, just trying to help.

[Stewart Loy]

Gents,

Thanks for the replies.

The new engine had an automatic transmission - so a new bushing was installed. The input shaft of the transmission fits snug and rotates freely.

The noise is gone when the clutch pedal is all the way up, with the transmission in or out of gear. I took a little drive down the driveway this morning and it does not make any noise when the vehicle moves. When the vehicel is moving, and the clutch pedal is pushed in - it growls.

I did not check the alignment of the engine to the transmission. It all fell together when I got it back from the machine shop. The clutch does not seem to slip - it certainly does not smell like it is.

The splines are OK on the input shaft and the TO bearings fit well. The release fork does not contact the bearing - it just pushes it - there should be lots of clearance (right?). The pressure plate fingers are all unbent. I assume that the machine shop cleaned them when they put it on the back of the engine with the clutch housing.

I believe that the clutch disc is in the correct way around.

Thanks for you thoughts on this. I shall get the manual out and see if the transmission is centred on the crankshaft.


Stewart

[Rhett Fisher]

Just a thought Stewart, is the crankshaft endfloat within limits? If so, it sounds like a case of clutch overthrow to me. Does the noise only occur when the pedal is pushed right down?
Rhett.

[Phil Waterman]

Hi Stewart

You mention that the engine just came back from the machine shop and that you are using the original 216 flywheel. Couple of thoughts any indication of movement fore and aft as the clutch is pushed in. Is the growl more of a rumble or a scraping and does it change note as the RPMs change? I'm thinking maybe fore aft play on the crank.

Now we have to figure how to post sounds so that we can better long range diagnostics.

When I reassembled the Pattern 12 Chey I forgot to really check the spline on the clutch plate and transmission shaft had a devil of a time shifting gears because the clutch would not always release fully, was just about to pull the transmission and clutch when it decided to free up by itself.

[Stewart Loy]

Rhett and Phil,

I am not sure what crankshaft endfloat is - might I know it as endplay in the crankshaft? The fore and aft movement of the crankshaft? I am not sure how to verify that condition. I imagine that I need some to allow the rotating assembly to spin around.

The noise that the system makes starts when the throw out bearing starts to spin - all the way to the end of the travel of the fork. The failed ball bearing noise is as if there were no lubricant of any kind in the rotating assembly. All racket stops when the clutch pedal is released and the bearing stops spinning. Oddly, the bearings are full of lube when removed - and seem OK. The clutch seems to release OK when the pedal gets pushed in when the freeplay is adjusted per the book.

I have only experienced this condition at idle - and it is not really loud - just enough to let me know that something is amiss. I put some grease on the splined shaft and it seemed to shift all right. The tranny guy suggested antiseize would be better - and very little so as not to contaminate the friction material.

I did not want to pull the pressure plate and disc but it seems like they need to come out to do the runout veriifcation that the manual advises. I am busy getting the T-16 for a Warriors Day parade on Saturday so any more ideas that will keep me out of that rotating assembly would be greatly appreciated.

Has anyone ever done the repairs to correct a misaligned transmission whilst installed in a CMP truck? I really don't want to wear out the bolts that hold the sheet metal on by removing all that kit (again).

I appreciate you musings on this - even Peters .


Stewart

[David Ellery]

Hi Stewart , Probably of no help, but I had a similar problem with my carrier after fitting the drive line in place. Thought it was the throw out bearing which I replaced, but found that the new one made the same noise. after heavily lubeing the fork where it sits in the throw out bearing the noise hasn't come back since.
David...