VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Mystery clutch noise

Yawl about got this worked out? Then I don't need to say anything? Good.

As they said in "My Fair Lady" "I think (s)hes got it." "The rain in Spain is mostly on the plain." "By God (s)hes got it."

Thanks, I think your're right, now if I can just convince my mechanic!

Kelly

Pardon me, but when I disassemble an early 6-cylinder I find the "pilot bearing/bushing" is pressed into the end of the CRANKSHAFT .

Either I don't understand the problem or "nomenclature" has taken a hike.

That sounds right, but both ends of that shaft are held in place with "pilot" bearings so if it's not the one in the flywheel than it has to be the ones in the transmission, hopefully.

The noise should occur anytime the engine is running and clutch depressed. If you let the engine idle in neutral, clutch not depressed, and you don't hear the noise then it is likely the flywheel side, if you hear the noise then it is likely the transmission side.

If you fill the transmission with oil and the noise goes away, problem solved.

Brian

I think that the problem here is one of nomenclature and everyone needs to get on the same page as to what they are calling a "Pilot Bearing". The bearing that is in the end of the crankshaft is called the "crankshaft clutch pilot bearing". If there is a bushing in the crankshaft instead of a bearing, then it is called the "crankshaft clutch pilot bushing".

Also, the "crankshaft clutch pilot bearing" (or bushing) turns whenever the crankshaft is turning.

I'm voting for the throw out bearing being the culprit. To go back to the original post, the noise occurs occassionaly and only after sitting for a while with the clutch disengaged. At that point, the t/o bearing would have been rotating for a while and, if not properly lubricated, could be building up heat and starting to "growl". Also stated was that it "....has what appears to be a brand new clutch assembly". If the previous owner had to replace the clutch because it was slipping too badly to sell, but didn't want to replace the t/o bearing in order to save a few bucks, maybe it is worn out as well. Wasn't the '38 t/o bearing the first year for a sealed bearing? I know my '37 coupe has a small inspection cover that can be removed to lubricate the t/o bearing, but that's a graphite bearing and I think it was redesigned for '38.
Lastly, I'd make sure the clutch pedal adjustment is correct and not riding on the clutch and that the t/o bearing fork isn't hitting the rotating assembly when the pedal was depressed all the way.
My 2¢

-Bob

I have a 1940 Chevy that I have owned since 1963 and have put ove 370,000 miles on it and it still has the original pilot bearing (needle type) installed. The bushings came later. I have changed many throwout bearings over the years but have never messed with the pilot bearing. And I have had the same problem you have. The throwout bearing will not always make the same noise or any noise everytime you depress the clutch. If your car is like mine it knows exactly when there are people present to hear uncalled for noises. I've read all of the replys to your questions and my vote stays with the throwout bearing.

I just hate being corrected by a dog....

Arf Arf! ha ha! :eek:

Your explanation is good enough to understand and it is correct.
To Check if the throwout bearing is causing the noise. Simply spray some penetrating oil around and into the back side of the TO bearing, then run it to see if the noise subsided. You can also remove the small inspection cover on top of the bell housing to observe what is happening at the throwout. It is obvious that the transmission and clutch assembly will have to come out, as it will not fix itself.
Secondly it is extremaely likely that the crankshaft pilot bearing (roller) is completely worn out and has destroyed the end of the input shaft. I have removed a number of crankshaft pilot bearings and bushings and the bearings do the most damage (Although they last for years) Replace it with a new bushing! With all of this wear on the front it all transfers down the line for a shaky clutch.

Sounds like what I went through with the 52, it turned out to be lack of lubricant in the pilot bearing. I relubed carefully using high temp white grease where the transmission shaft and the pilot bearing mate care not to get carried away and have had no trouble through over 3 years of driving in parades, around town etc.

And if the crankshaft has excessive end float you can get a noise when the clutch is depressed because it pushes the crankshaft forward. The source of the noise can depend on how worn the thrust is. It is an easy thing to check before you start pulling things apart.

Ken

Did you greese the pilot bearing?

Well, after replacing the motor and transmission mounts, fixing the leaks in the transmission and filling it back up with oil, my mystery clutch noise is.....still there.
The mechanic was sure it was the pulley grinding on the frame because nothing was holding the engine in except the driveline, but after I drove it around for awhile, sure enough, it came back in all it's growling glory. My wife said she could even hear it in the house as I pulled into the driveway, but at least this time I can make it happen at will. Just warm the car up real good by driving around for a half hour and then with it stopped and in gear and with the clutch pedal held down, rev the engine. Grrrrrrrrrrrrrrr until you let the clutch out.
Now at least I can take it back to my mechanic and let him hear and feel it for himself.
I'll keep you posted!

Kelly

By what I have read the bearing (bush)at the front of the gearbox in the crankshaft is the problem. The only way to fix the it is to separate box and motor. While it is all apart advisable to check condition of clutch and flywheel, repair or replace as neccessary.