Throw out bearing - what cause this?

[Donald H.]

I'm helping with some work on a 66 (not my car). We are actually doing a frame swap to a new Vette Products frame. The car ran and drove fine, but we are going to clean and paint the engine. After pulling the engine we removed the transmission, bellhousing, clutch assembly and flywheel.

The two attached pictures are of the throw out bearing alone and the bearing mounted in the fork. Note the bend in the bearing rear lip.

Any idea what could have caused this?

The owner had a lot of work done on the car shortly after he purchased it, including new flywheel and clutch assembly. I'm no expert, but the flywheel appears to be a lightweight one. I'm not near the car now, but I'm going to measure the flywheel thickness at the crank mounting surface to the friction face of the flywheel. I know the OEM was 1.00".

If the flywheel is much thinner, could that cause the throw out bearing to be pushed in so much more to release the clutch that the lip gets bent by the fork? I'm just guessing here!!

Thanks,

Don

[Tim S.]

Re: Throw out bearing - what cause this?

I'd say the fork was not properly sitting on the ball and thus the bearing was not centered. The pedal pressure had to immense!

Tim

[Gary B.]

Re: Throw out bearing - what cause this?

…I'm no expert, but the flywheel appears to be a lightweight one.

Don,

The original GM flywheel weighed 30 lbs. Although original, refurbished flywheels can be bought for not too much money, new 30 lb flywheels can be expensive, e.g. twice as much as light weight ones. If the earlier clutch replacement work was done on a budget, perhaps a lighter weight flywheel was used, which tend to be substantially cheaper.

Or maybe as I think you’re speculating, the original flywheel was excessively resurfaced, making it significantly lighter?

Gary

[Donald H.]

Re: Throw out bearing - what cause this?

I'd say the fork was not properly sitting on the ball and thus the bearing was not centered. The pedal pressure had to immense!

Tim

Maybe at one time, but when I took it apart, the fork was correctly attached to the ball and the bearing was installed correctly to the fork.

[Timothy B.]

Re: Throw out bearing - what cause this?

Donald,

I think you first thought about the flywheel being thinner may be something that could cause this issue, I don't think I've ever seen this before.

I would also verify the correct clutch linkage for the car and sort of start over with things making sure everything is in spec when assembling.

[Larry M.]

Re: Throw out bearing - what cause this?

Original 30 lb flywheel is 0.970 inches thick.

Larry

[Donald H.]

Re: Throw out bearing - what cause this?

The fellow who owns the car is on a one year overseas assignment, but I was able to email him and get some more info. The clutch is a LUK, so that makes me feel better.

The flywheel is from NAPA and looking at the website doesn't provide much info. Pictures from the website of the particular flywheel attached. They also sell one labelled as OEM, but that isn't what was installed on his car.

I'll measure it when I get back over to the car and see if it's close to OEM spec. Also, it does have the 1 3/8" ball.

Don

Don

[Mark F.]

Re: Throw out bearing - what cause this?

WOW...maybe I'm seeing an optical illusion in the second photo, but could someone have used the wrong bearing w/o the proper trough spacing (width?) and pounded it into the fork causing the bend to be there from day one it was installed?

Was the bearing "squealing" before you guys pulled it?

I'll bet the way you show it in photo 2 is the only way it fits in that fork. Can you rotate it 180 degrees in the prongs? probably not??

Do you have a replacement bearing?
Does it fit properly in the fork?

Only other option I see from your photo is the fork is too thick at the yoke (wrong fork?)
I'm no expert, but I've changed out 5 or 6 throwouts in my time and never saw anything like that.

[Donald H.]

Re: Throw out bearing - what cause this?

WOW...maybe I'm seeing an optical illusion in the second photo, but could someone have used the wrong bearing w/o the proper trough spacing (width?) and pounded it into the fork causing the bend to be there from day one it was installed?

Was the bearing "squealing" before you guys pulled it?

I'll bet the way you show it in photo 2 is the only way it fits in that fork. Can you rotate it 180 degrees in the prongs? probably not??

Do you have a replacement bearing?
Does it fit properly in the fork?

Only other option I see from your photo is the fork is too thick at the yoke (wrong fork?)
I'm no expert, but I've changed out 5 or 6 throwouts in my time and never saw anything like that.

The bearing did not make any noticeable noise when driving. The bearing itself will spin freely.

I have ordered a new National throw-out bearing and a new GM OEM fork.

Don

[Donald H.]

Re: Throw out bearing - what cause this?

I looked at NAPA again, the one pictured above is the only one that fits the C2 small block. The one I saw that was listed as OEM is 168 tooth larger flywheel.

Also, the NAPA one I have pictures is most probably the LUK LFW131, or at least the LFW131 on Summit's website looks exactly like the NAPA 88131.

Don

[John P.]

Re: Throw out bearing - what cause this?

Hello Donald, The collar on the throw out bearing is too short, allowing the inside radius of the fork to bend the collar when the clutch is depressed. There are at least three different thickness (height) throw out bearing collars available and you will have to choose the correct length to position the fork in the proper position. It looks like you may need a bearing with a 1/4 inch thicker bearing collar. Several clutch manufacturers supply the most popular bearing with their kits. In many cases, the bearing collar is not the correct length required.

[Douglas L.]

Re: Throw out bearing - what cause this?

1967ClutchThrowoutBearingSize-6-2-160001.jpg1967ClutchThrowoutBearingSize-6-2-160002.jpg

Looks as if the throw-out bearing may be the culprit.

[Richard M.]

Re: Throw out bearing - what cause this?

Don was the inside groove of the bearing lubricated and is the trans shaft slippery or dry?

Rich

[Joe L.]

Re: Throw out bearing - what cause this?

I'm helping with some work on a 66 (not my car). We are actually doing a frame swap to a new Vette Products frame. The car ran and drove fine, but we are going to clean and paint the engine. After pulling the engine we removed the transmission, bellhousing, clutch assembly and flywheel.

The two attached pictures are of the throw out bearing alone and the bearing mounted in the fork. Note the bend in the bearing rear lip.

Any idea what could have caused this?

The owner had a lot of work done on the car shortly after he purchased it, including new flywheel and clutch assembly. I'm no expert, but the flywheel appears to be a lightweight one. I'm not near the car now, but I'm going to measure the flywheel thickness at the crank mounting surface to the friction face of the flywheel. I know the OEM was 1.00".

If the flywheel is much thinner, could that cause the throw out bearing to be pushed in so much more to release the clutch that the lip gets bent by the fork? I'm just guessing here!!

Thanks,

Don

Don------


Maybe it's my imagination or just the photo but the fork groove width on this bearing looks wider than it should. The proper width is 0.50". What is the as-measured width of this one?

[Donald H.]

Re: Throw out bearing - what cause this?

Don was the inside groove of the bearing lubricated and is the trans shaft slippery or dry?

Rich

Rich,

The input shaft cover is dry and I don't recall any lube on the bearing groove.