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I have been driving my car for years and my clutch was starting to slip. When I took it apart, I was dumbfounded why the throw-out bearing was cracked (see photos). I bought a new one and put everything back together. When I went to go push in the clutch, it felt like something was stopping it, then I heard this "BANG"!!
I couldn't figure out what that was...perhaps the gorilla spring I thought?? So I tested out the car, all seemed to be good, shifted fine, except I had a problem with the clutch sticking to the floor (which many people have encountered) when I got it from a stop light. If I shifted like a granny, no problem.
While adjusting the play/g-spring...something didn't seem right, so I took off the inspection plate and I could see that the TO bearing wasn't tight and I discovered a dent...similar to the one that cracked. Needless to say, I'm perplexed as hell.
My only thing I can come up with is perhaps a problem with the clutch fork.
I have measured the ball joint that the fork attaches to (LAR's write-up) and that was right.
And yes, I had the TO bearing seated correctly on the fork.
Anyone have any thoughts on this?
Last edited by jusplainwacky; 07-12-2021 at 08:13 PM.
Just a guess, based on your photos. Looks as though the fork (see worn-away paint) is distorted where it bears on the TO, and instead of applying pressure uniformly, it's placing all of the load on the outer edge the mating surface. Taking it further, when that one spot snapped off, the opposite side was taking every bit of the load, which loaded the bearing in a non-axial direction, causing further failure.
Just a guess, based on your photos. Looks as though the fork (see worn-away paint) is distorted where it bears on the TO, and instead of applying pressure uniformly, it's placing all of the load on the outer edge the mating surface. Taking it further, when that one spot snapped off, the opposite side was taking every bit of the load, which loaded the bearing in a non-axial direction, causing further failure.
Live well,
SJW
It's not distorted.
I'm searching the forum for photos and although it's hard to tell, it looks like to me that the arc from the from the flat side of the fork to where the hole is for the push rod pin is not correct. The correct one seems to have less of an arc.
Make sure the bell housing is also correct for the year. I had problems and found that I had a truck bellhousing that a prior owner had installed. it fit the small block chevy but the correct fork did not jive geometrically
Went down a similar road in the mid 70's. found previous owner liked drag racing and had installed the wrong fork and pivot ball. The L-88 needs a mountain of clamping force which turns the clutch pedal into a serious leg press, lotta stress on linkage.
Someone else posted a thread in the last year about a TO bearing with similar damage on the flange. I don’t recall the cause but maybe someone will recall it.
Yours appears like a 64+ fork based on the angled end where the pivot pin attaches.
The 56-62 end is nearly parallel to the arm.
Hey Rich....to me it doesn't look like a 64+ photo...it looks like it's in between, but it's also hard to just compare photos as camera angles can be deceiving.
I'm hoping someone can duplicate my measurements.
Last edited by jusplainwacky; 07-12-2021 at 09:54 PM.
Make sure the bell housing is also correct for the year. I had problems and found that I had a truck bellhousing that a prior owner had installed. it fit the small block chevy but the correct fork did not jive geometrically
Dan that might have been me but several years ago. It was on a 66 though.(member cor66vette in Fl). I did a body off on it to replace a rusted frame and when I split the trans/engine apart, one ear of the fork was offset and that sides flat spring tip was missing. It broke a chunk from the bearing circular flange just like Dennis's. It was still working before I took it apart.
Dennis, yes your fork is like its in between both types, and the effect of using a 64+ fork on a C1 is that it changes the geometry of the rod mechanism and the attach points of the clevis to the lower Z-bar position. This causes improper operation using a stock fork rod.
Your rod may have been modified from stock, if so, shortened.
It appears some of your parts are not stock and have strained or offset the bearing, in addition to creating a unusual free play value you spoke of.
If I were you I would simply acquire proper new parts. This way you have a proper mechanism baseline to work with.
PR in a diamond is the Paragon Reproctions logo. P is a logo found on some original other type stamped steel parts as well.
Find the GM part# for the 56-62 fork. I have no ref docs handy where I am. Plug it into gmpartswiki.com. You will likely find many other applications.
When you look at buns and Herm's fork photos, you can see that yours is angled much more than a stock C1 fork. The end angle on a stock C1 fork is nearly 90* where the C2 fork is quite a bit more.
edit.....
One other item I just noticed....
The rearward flange of your TO is bent. Like the fork finger got jammed on it during pedal release and bent it, whereas the other fork finger may have strained its contact point and broke a chunk off.
The only thing I can think of that caused this would be if the bearing hung up on the trans shaft sleeve.
If the bearing ID and sleeve was dry this might be a cause. There's a grease groove inside the ID of the bearing. This should be packed with grease just in that groove to ensure free longitudal movement on the sleeve.
If it was dry, this may have been that bang you heard first time after new clutch was installed..... I.E. it hung up on the sleeve, was cocked sideways, then banged when it finally slipped away. It may have broken that piece off on your first pedal push.
Rich... I agree. Off to find another fork.
The GM Part number for a 1957- 62 Corvette Clutch Release Fork – #3739043
Dennis,
Here are the pictures and some measurements off the fork I received from Corvette Central in about 2005, for my 62. Note that it also has the PR logo stamped on it. It has never been used. It measures ~10.375" long, has a 1.665" gap between the fork tines, the kick up at the rod end measures about 2.763" long, and the 2 tines measure 3.551" at the outer edges. Also, if the body is held square horizontally , the rod end "kick up" is about 1.75" from the main body (first picture).
If you need additional measurements, just ask.
Plasticman
Last edited by Plasticman; 07-13-2021 at 11:46 AM.
John....thanks for the photos and measurements. I obviously have the wrong fork. Seems crazy that for all these years I have been driving around with it and a broken TO bearing.
A few years ago I bought a NORS clutch fork from Doc Rebuild, and it was just a few dollars more than a repro. Doc's website appears to be back up, so maybe give that a try.
Dan that might have been me but several years ago. It was on a 66 though.(member cor66vette in Fl). I did a body off on it to replace a rusted frame and when I split the trans/engine apart, one ear of the fork was offset and that sides flat spring tip was missing. It broke a chunk from the bearing circular flange just like Dennis's. It was still working before I took it apart.
07-12-2021, 06:42 PM
Correct clutch fork? What the heck is going on???
