65 LUK throwout bearing

[John M.]

I'm having some problems with the adjustment of the freeplay on a new LUK clutch and throwout bearing. The question is does anyone have a C2 LUK clutch that's about to go into the car and if so what is the overall length of the bearing assembly? The bearing that came out was 1.25" long and I didn't measure the new one, just put it together and put the clutch, bellhousing and transmission in the chassis. I'm thinking that the bearing is too long but need some positive info before taking anything apart.
Thanks,
John McRae 30025

[Joe L.]

Re: 65 LUK throwout bearing

I'm having some problems with the adjustment of the freeplay on a new LUK clutch and throwout bearing. The question is does anyone have a C2 LUK clutch that's about to go into the car and if so what is the overall length of the bearing assembly? The bearing that came out was 1.25" long and I didn't measure the new one, just put it together and put the clutch, bellhousing and transmission in the chassis. I'm thinking that the bearing is too long but need some positive info before taking anything apart.
Thanks,
John McRae 30025

John------


The correct release bearing is 1-1/4" long (actually, the original bearing was 1-7/32" long but that bearing has not been available in over 30 years). The other common bearing, used on many other Chevrolet applications but not Corvette (except 1955), is 1-7/8" long. There is NOT a subtle difference in this bearing length and appearance and I would think that you would have instantly noted the difference when installing it.

What is the part number of the LUK kit you used?

[Joe C.]

Re: 65 LUK throwout bearing

I'm having some problems with the adjustment of the freeplay on a new LUK clutch and throwout bearing. The question is does anyone have a C2 LUK clutch that's about to go into the car and if so what is the overall length of the bearing assembly? The bearing that came out was 1.25" long and I didn't measure the new one, just put it together and put the clutch, bellhousing and transmission in the chassis. I'm thinking that the bearing is too long but need some positive info before taking anything apart.
Thanks,
John McRae 30025

John,
Did you replace the flywheel? If there is any difference in the positioning of its friction surface from a stock unit, this will upset the geometry of your clutch linkage in the same way as TO bearing length. Your pressure plate should be a straight finger type diaphragm.
Explain the trouble you're having.
Joe

[John M.]

Re: 65 LUK throwout bearing

Thanks Guys,
Joe L. There was about 15 months between the take out of the old and the putting in of the new so I never thought about the lengths, it may be the same as the old... tough getting older. The Luk is the 04-021.
Joe C. The flywheel was just resurfaced. The clutch works ok it's just that I have the adjustment at the upper end of the rod thread. I have two other cars with LUKs and the nuts are more or less in the middle. The clutch that was in the car worked fine but had been in there a very long time. How many miles, don't know. That throwout bearing was 1.25"
If the LUK kit has the 1.25" bearing then something else is wrong, but what?
I should send you a photo of the pressure plate that was in the car; it was balanced(?) by welding on a chunk of a steel rod.
John

[Joe C.]

Re: 65 LUK throwout bearing

Thanks Guys,
Joe L. There was about 15 months between the take out of the old and the putting in of the new so I never thought about the lengths, it may be the same as the old... tough getting older. The Luk is the 04-021.
Joe C. The flywheel was just resurfaced. The clutch works ok it's just that I have the adjustment at the upper end of the rod thread. I have two other cars with LUKs and the nuts are more or less in the middle. The clutch that was in the car worked fine but had been in there a very long time. How many miles, don't know. That throwout bearing was 1.25"
If the LUK kit has the 1.25" bearing then something else is wrong, but what?
I should send you a photo of the pressure plate that was in the car; it was balanced(?) by welding on a chunk of a steel rod.
John

John,

You probably know this already, but, the business end of the clutch fork is too close to the crankshaft. But why? Either the flywheel is too thin, which is doubtful. More likely something in the pressure plate geometry is not right. Are you sure it's a straight finger and not a bent finger? I assume you are using a stock, non-adjustable ball stud.

[John M.]

Re: 65 LUK throwout bearing

Joe, To be honest I don't know what it is other than a LUK standard replacement 04-021. I just bought it and put it in there without a thought because I've done it before with zero troubles. If someone can tell me the throwout bearing length for the LUK I can either eliminate that as the source or fix it. There's all the linkage pieces and the Z bar but none of that has been changed so either two wrongs made it right before or it's the bearing. It's not a disater but I have the need to know, if you know what I mean.
John

[Joe C.]

Re: 65 LUK throwout bearing

Joe, To be honest I don't know what it is other than a LUK standard replacement 04-021. I just bought it and put it in there without a thought because I've done it before with zero troubles. If someone can tell me the throwout bearing length for the LUK I can either eliminate that as the source or fix it. There's all the linkage pieces and the Z bar but none of that has been changed so either two wrongs made it right before or it's the bearing. It's not a disater but I have the need to know, if you know what I mean.
John

All Corvette TO bearings are 1 1/4" long.
It's possible that LUK mislabeled your PP and you installed a bent finger unit. Only way to know for sure is to drop the trans and look at it.
Joe

[Joe L.]

Re: 65 LUK throwout bearing

Joe, To be honest I don't know what it is other than a LUK standard replacement 04-021. I just bought it and put it in there without a thought because I've done it before with zero troubles. If someone can tell me the throwout bearing length for the LUK I can either eliminate that as the source or fix it. There's all the linkage pieces and the Z bar but none of that has been changed so either two wrongs made it right before or it's the bearing. It's not a disater but I have the need to know, if you know what I mean.
John

John----

LUK #04-021 is the correct kit for your application. It should contain a 1-1/4" release bearing. So, unless it was mis-boxed or unless someone change the components of the kit before you got it, it should have contained what you need.

[Edward J.]

Re: 65 LUK throwout bearing

John, I have seen this before and the reason is as Joe C. states when a flywheel is machined maybe more that once, it get thinner. you'll need to put a shim between the crankshaft and flywheel to make up the difference, They come in a few different sizes depending on how much was machined off the flywheel , theres a chance that it may have had a few clutch replacements and each time the flywheel was machined.if everything is already back together, there is one more thing can be done and that would be to use a 66/67 clutch push rod. its slightly longer and will give you more adjustment. GOOD LUCK, ED

[John H.]

Re: 65 LUK throwout bearing

All Corvette TO bearings are 1 1/4" long.
It's possible that LUK mislabeled your PP and you installed a bent finger unit. Only way to know for sure is to drop the trans and look at it.
Joe

Joe -

The original midyear clutch was a "bent-finger" unit, like the one in the photos you posted (same as the LuK #04-021), which is why they used the 1-1/4"-long throwout bearing; passenger cars also used a diaphragm clutch, but it was a "flat-finger" unit, and used the longer 1-7/8" throwout bearing. Photo below shows the "flat-finger" unit.


FlatFingerClutch.jpg

[Chuck G.]

Re: 65 LUK throwout bearing

Did you install the TO bearing correctly in the clutch fork?

Here's a pic of the correct and incorrect ways to do it.

Chuck

[John M.]

Re: 65 LUK throwout bearing

Thank you, everyone, for the replies.
The throwout bearing was installed correctly, I think. I've done it quite a few times but there's always a first.
The flywheel was resurfaced but just a touch (he said) but I did not measure it.
I now believe that the throwout bearing is the 1 1/4" one because it came out of the box with the 04-021 so it must be something else but what?
I suppose it could be an incorrect replacement clutch assembly rod but it's not logical as the old clutch was right in the middle of the threads. (Why did I replace it?) It had been in there a long time but the usage was unknown.
The clutch works fine but the nuts are at the upper end of the threads and I need to know why. A project for the long winter here, I guess. I'll post the solution when I find it.

[Timothy B.]

Re: 65 LUK throwout bearing

John,

If it's got the correct clutch rods and the correct 1 1/4" throw out bearing and it adjusted fine before the replacement my next call would be the LUK clutch company. The flywheel has a taper around the circumference and that is what I always thought was the point where you need to replace the flywheel.

I had a problem with the clutch in my 67 when I bought it years ago, if I adjusted for free play the clutch would not dis-engage or if I adjusted so it disengaged there was no play for the T/O bearing. Sent it out for overhaul, when it came back it was fine. The problem had something to do with the pressure plate shimming. I think if they turn the pressure plate it needs to be shimmed for the height to be correct but double check this. If you clutch is new then something with the P/P is not right.

If I got it right you will not have any adjustment when the clutch disc wears.

[John M.]

Re: 65 LUK throwout bearing

Thanks Tim,
I think the problem is the opposite. The nuts are at the top of the rod, near the firewall; it's as if the throwout bearing is too long. I was looking at the old clutch last night and the disc looks good but the pressure plate has been messed with. It has three different bolts holding it together, two grade 5, one grade 8 so without something to compare to I am unable to tell if it's different from the present LUK model in the car. The total adjustment length on the clutch rod probably represents very little travel of the TO bearing so the difference may be subtle. I don't need to do anything right now but you know this will drive me nut's until I get it straightened out.
John

[Joe L.]

Re: 65 LUK throwout bearing

I should send you a photo of the pressure plate that was in the car; it was balanced(?) by welding on a chunk of a steel rod.
John

John-----


Very common on both original pressure plate assemblies as well as those that have been balanced by balancing shops. Commonly welded on balance weights are steel rod and large washers.