[RJB68GTO]

it has been a while and have a question about what clutch to use in my 68 GTO. Although it is a 68 the motor and tranny had been changed way before I got the car to include a 69 YS 400 block converted to the original 4 spd of the car. However I have recently found that the tranny had also been changed from the original, it is now an Muncie case part #3925660 id'ed as a 1969 GM transmission with speed-o-meter on the right side. The YS motor has had the heads replaced with #16 heads ,as my guess, the HO heads from the original WS motor and upgraded to include a mild cam which I have no specs on.

Currently I am experiencing problems with the clutch with low rpm chatter/vibration and most recently have been having trouble down shifting the car, in fact I am unable to downshift until I come to a complete stop and there is a whining sound when I try to do so. The pedal just does not feel right as if the clutch is not full engaged/unengaged. I have lengthened the clutch rod which seems to help reduce the chatter vibration but not the downshift issue.

I am going to buy a new clutch kit and was wondering what would be a good replacement without breaking the bank. Any recommendations would be much appreciated. The car up to this point has always run strong with no issues, it shifted well in the 4-5,000 rpm range when I got on it.

Thanks in advance for your help.

[johnta1]

Generally, the problem is probably the throwout bearing.
The bearing has to match the pressure plate being used.
Diaphragm use a different type than the three finger type of pressure plate.


For general use the Diaphragm type will work good on the street, with easier 'leg' push. (usually)

[tom s]

A good test is when you start up the engine,have in neutral and then put it in a forward gear but dont let the clutch out,then try to put it in reverse,if it grinds the disk is dragging.Tom

[gtobob67]

Luk Clutch from Rock Auto.

[RJB68GTO]

Originally Posted by gtobob67

Luk Clutch from Rock Auto.

Thanks, I looked into those and may be an option but was hoping to buy American, they are made in Korea.

[RJB68GTO]

Originally Posted by tom s

A good test is when you start up the engine,have in neutral and then put it in a forward gear but dont let the clutch out,then try to put it in reverse,if it grinds the disk is dragging.Tom

Thanks I will try that, appreciate the response.

[RJB68GTO]

Originally Posted by johnta1

Generally, the problem is probably the throwout bearing.
The bearing has to match the pressure plate being used.
Diaphragm use a different type than the three finger type of pressure plate.


For general use the Diaphragm type will work good on the street, with easier 'leg' push. (usually)

Thanks for the reply much appreciated, I know that the throw out bearing we used was new and came with the clutch but am finding out that that might not be the bearing that is needed will check options when I select a new clutch. Good info.

[RJB68GTO]

Originally Posted by tom s

A good test is when you start up the engine,have in neutral and then put it in a forward gear but dont let the clutch out,then try to put it in reverse,if it grinds the disk is dragging.Tom

Just tried this test and #1 I could not get the tranny in 1st from neutral, therefore I could not try to pot into reverse from that position. But I tried to put the tranny in reverse right from neutral and boy did it start to grind. Guess I'll go order that new clutch kit now.

Thanks.

[PontiacJim1959]

Attachment 545733FYI, here is the difference in the "long" vs "short" throw out bearing. Sometimes the clutch kit will not have the correct bearing - had this happen with a new McLeod set-up and had to pull the trans back out after I pushed in the clutch and it went near the floor, you cannot adjust this out. LOL

The faces can also be different, as seen in photo 3 for a comparison, so if ordering a replacement because you got the wrong one, you want to match it up rather than just grab any local store brand just because it is opposite of what you needed.

You can check this before putting in the trans by installing the clutch fork and observe where the arm is positioned based on the bell housing hole it sticks out through. It should be closer/angled to the front, than angled to the rear.

Seems a number of users like the LUK brand set-ups, but I personally have never used one.

[tom s]

You might only need the correct throw out bearing!Tom

[salem1912]

Originally Posted by RJB68GTO

Just tried this test and #1 I could not get the tranny in 1st from neutral, therefore I could not try to pot into reverse from that position. But I tried to put the tranny in reverse right from neutral and boy did it start to grind. Guess I'll go order that new clutch kit now.

Thanks.

When you try to put in 1st from neutral try while holding pressure to go into 1st and shut car off. If it drops into 1st your clutch is dragging. If it still won't go in you may have a sync problem.

[RJB68GTO]

Originally Posted by salem1912

When you try to put in 1st from neutral try while holding pressure to go into 1st and shut car off. If it drops into 1st your clutch is dragging. If it still won't go in you may have a sync problem.

Okay just tried that and in fact while applying pressure to put in 1st and it not going in and shutting car off it does go into first easily.

This is getting aggravating, damn thing worked fine with no issues 10 or so days ago went for a nice drive just cruising then let it set because of the 90* heat and then last Sunday decided to go for a short ride and bam could not down shift. Adjusted clutch rod adding about a 1/4" in length which helped the chatter a little like I said but did not help the shifting problem but I could get it in gear and back out of garage and then today trying your test it just would not go in gear after starting it in neutral and I don't dare try to start it in gear just to see it lunge back or forward depending on what gear I put it in even with the clutch in. I'm now thinking I did not help myself by lengthening the clutch rod as the pedal lash is now less than an " and the pedal is all the way on the floor.

Again thanks for the tip also it goes into any and all gears with the engine off so pretty sure it is the clutch where my problem lies.

[RJB68GTO]

Originally Posted by PontiacJim1959

Attachment 545733FYI, here is the difference in the "long" vs "short" throw out bearing. Sometimes the clutch kit will not have the correct bearing - had this happen with a new McLeod set-up and had to pull the trans back out after I pushed in the clutch and it went near the floor, you cannot adjust this out. LOL

The faces can also be different, as seen in photo 3 for a comparison, so if ordering a replacement because you got the wrong one, you want to match it up rather than just grab any local store brand just because it is opposite of what you needed.

You can check this before putting in the trans by installing the clutch fork and observe where the arm is positioned based on the bell housing hole it sticks out through. It should be closer/angled to the front, than angled to the rear.

Seems a number of users like the LUK brand set-ups, but I personally have never used one.

Thanks, at this point I do not recall if we used a tall or short throw out bearing on the existing clutch it was what ever came with the kit. Which one would angle the end of the fork more towards the front, I'm thinking the tall one, but at this point what the hell do I know.

[PontiacJim1959]

Originally Posted by RJB68GTO

Thanks, at this point I do not recall if we used a tall or short throw out bearing on the existing clutch it was what ever came with the kit. Which one would angle the end of the fork more towards the front, I'm thinking the tall one, but at this point what the hell do I know.

First, count to 3 and take a deep breath! LOL Sometimes being frustrated makes the obvious unobvious. Now, sorry for the long story, but.........

The pressure plate, diaphragm types, can be either a flat or raised finger design. The clutch fork also comes into play as it can have a different pivot point and angle.

Do you know for a fact that you have Pontiac replacement parts that are correct for your year/build? I experienced the purchase of a "generic" aftermarket clutch fork said to fit my '68 Lemans. I was thinking that while I am installing all new clutch linkage and clutch set-up, might as well spring for the fork. Mine was ok, but while I am replacing everything..........

The aftermarket fork looked OK eyeing it up, but it was not Pontiac. I decided to also install an adjustable pivot ball in the bellhousing to replace the original. The aftermarket pivot ball had a broader "head" that the dimple on the clutch fork pivots on. Problem #1 that I did not see. Problem #2 was that the aftermarket clutch fork had a larger and deeper spacing where it slips over the throw-out bearing. Didn't think of it much at the time. Problem #3 was that the throw-out bearing was too short for the McLeod clutch set-up kit I had received (been told it was for a Chevy application?) and of course this was not learned until I fired up the car and went to put it into gear. Knew what it was right away from the same issue in my youth - so had to pull everything apart to install the correct length throw-out bearing.

Ok, new bearing in and now it'll go into gear no problem and the car drives. BUT, Problem #1 and Problem #2 rear up its ugly head. The "generic" clutch fork with its larger than stock deeper spacing, slips off the wider pivot head of the pivot ball on a nice hard fast shift. I go to push the clutch in for the next gear and no go. Pedal goes down and it is not enough to shift gears. Bad sound coming from the clutch set-up as well. I managed to limp home.

Pull out the trans and what I found was that the generic clutch fork had slipped off the pivot ball, and deeper over the throw-out bearing collar to the point the 2 contact arms that contact the throw-out bearing when you push in the clutch pedal went past the bearing and seated the fork deeper into that oversized opening. When it did that and I pushed in the clutch, the clutch fork pivoted not on the 2 contact arms, but the thicker arms that go around the throw-out bearing collar and busted off a big section of the throw-out collar. That section in turn went sailing into the pressure plate at speed and literally took out a damper spring in the clutch disc.

Went and located an original used 1968 clutch fork because I had tossed the original one out (heck, I had a new replacement so why hang onto junk, right?) and then shaped the pivot ball head on the adjustable pivot ball to fit correctly in the '68 clutch fork pocket. Noted that the factory fork did not have the extra large & deep spacing as did the generic fork which would not allow it to override the throw-out bearing collar as the generic fork had - very tight fit as it should have been. Had to anti-up for a new clutch set-up..............only to learn later that there are 2 different heads on the flywheel-to-crank attachment bolts.

Of course I got the Grade 8 flywheel bolts advertised to fit the Hays flywheel for Pontiacs only to learn I needed the thinner head on the bolts versus the thicker heads. Always had a strange whine when slipping the clutch out and I attributed it to the carbon fiber clutch disc as a normal type sound because I never ran a carbon fiber disc before. When I disassembled the engine for rebuild version 2.0, it was obvious that the thicker heads on the flywheel bolts were hitting/polishing the clutch disc springs - and that was where the strange whining sound was coming from. Those little springs were nice and shiny on the high side. LOL

Lesson learned - aftermarket advertised parts said to work or to be for your Pontiac may not be for your Pontiac because many of the sellers are just that, sellers and not Pontiac people, let alone actually work on cars. So it is up to you to check and confirm everything - which can be harder when the previous owner has installed non-Pontiac or generic "said to fit" parts and you don't know the difference between factory and aftermarket because you did not start with factory parts that could be used for comparison.

So start from the beginning and go throw the entire set-up from clutch pedal to linkages to clutch fork to the clutch set-up.

I'll spare you about the oil pump problem that took out my previous 400CI build and caused me to get wrapped up in my long term resto-mod 2.0 car rebuild - which I hope to get done before I die. LOL

[PontiacJim1959]

Drawing of what the clutch fork position should look similar to. The longer bearing will position the clutch fork closer towards the front of the engine versus back towards the rear of the car.

There is also a "medium" length throw-out bearing, but mostly you will see the short or long size.

[RJB68GTO]

Thanks for the reply and for all the details on what to look for it all helps.

The more I get into this the more I want to find the guy who replaced the original engine and tranny and drag his ass up and down the highway.

As I mentioned before and to your point I am not sure of anything on this car any more; engine is a 1969 YS motor which was originally tied to an automatic transmission with #62 heads, but was converted to the muncie 4 spd that came originally in the car ( the originall motor was a WS 400 ci HO motor with a 4 spd) and after running the #s and checking the heads currently on the car the originally #62 heads were replaced with #16 HO heads (I assume taken from the original $))HO motor the car was built with). Then running the numbers on the transmission I found that it is not an original pontiac numbered tranny but a 1969 Muncie GM replacement tranny for all GM a body cars (at this point and until I pull the tranny I do not know if it is an M20 or M21 tranny, therefore do not know if what I end up ordering for a clutch kit will be the right one but don't think that should be an issue as long as I get the correct release and pilot bearing/bushing. I do recall when we put in this clutch we had to use a roller type pilot bearing as the end of the crank was a larger diameter than a standard pilot bushing.
And after looking at the clutch linkage I am not certain that it is a true Pontiac linkage.
Well back at it looking for the right parts to do this job correctly. Will keep you posted thanks for the help. This forum has always come through for me.

Originally Posted by PontiacJim1959

First, count to 3 and take a deep breath! LOL Sometimes being frustrated makes the obvious unobvious. Now, sorry for the long story, but.........

The pressure plate, diaphragm types, can be either a flat or raised finger design. The clutch fork also comes into play as it can have a different pivot point and angle.

Do you know for a fact that you have Pontiac replacement parts that are correct for your year/build? I experienced the purchase of a "generic" aftermarket clutch fork said to fit my '68 Lemans. I was thinking that while I am installing all new clutch linkage and clutch set-up, might as well spring for the fork. Mine was ok, but while I am replacing everything..........

The aftermarket fork looked OK eyeing it up, but it was not Pontiac. I decided to also install an adjustable pivot ball in the bellhousing to replace the original. The aftermarket pivot ball had a broader "head" that the dimple on the clutch fork pivots on. Problem #1 that I did not see. Problem #2 was that the aftermarket clutch fork had a larger and deeper spacing where it slips over the throw-out bearing. Didn't think of it much at the time. Problem #3 was that the throw-out bearing was too short for the McLeod clutch set-up kit I had received (been told it was for a Chevy application?) and of course this was not learned until I fired up the car and went to put it into gear. Knew what it was right away from the same issue in my youth - so had to pull everything apart to install the correct length throw-out bearing.

Ok, new bearing in and now it'll go into gear no problem and the car drives. BUT, Problem #1 and Problem #2 rear up its ugly head. The "generic" clutch fork with its larger than stock deeper spacing, slips off the wider pivot head of the pivot ball on a nice hard fast shift. I go to push the clutch in for the next gear and no go. Pedal goes down and it is not enough to shift gears. Bad sound coming from the clutch set-up as well. I managed to limp home.

Pull out the trans and what I found was that the generic clutch fork had slipped off the pivot ball, and deeper over the throw-out bearing collar to the point the 2 contact arms that contact the throw-out bearing when you push in the clutch pedal went past the bearing and seated the fork deeper into that oversized opening. When it did that and I pushed in the clutch, the clutch fork pivoted not on the 2 contact arms, but the thicker arms that go around the throw-out bearing collar and busted off a big section of the throw-out collar. That section in turn went sailing into the pressure plate at speed and literally took out a damper spring in the clutch disc.

Went and located an original used 1968 clutch fork because I had tossed the original one out (heck, I had a new replacement so why hang onto junk, right?) and then shaped the pivot ball head on the adjustable pivot ball to fit correctly in the '68 clutch fork pocket. Noted that the factory fork did not have the extra large & deep spacing as did the generic fork which would not allow it to override the throw-out bearing collar as the generic fork had - very tight fit as it should have been. Had to anti-up for a new clutch set-up..............only to learn later that there are 2 different heads on the flywheel-to-crank attachment bolts.

Of course I got the Grade 8 flywheel bolts advertised to fit the Hays flywheel for Pontiacs only to learn I needed the thinner head on the bolts versus the thicker heads. Always had a strange whine when slipping the clutch out and I attributed it to the carbon fiber clutch disc as a normal type sound because I never ran a carbon fiber disc before. When I disassembled the engine for rebuild version 2.0, it was obvious that the thicker heads on the flywheel bolts were hitting/polishing the clutch disc springs - and that was where the strange whining sound was coming from. Those little springs were nice and shiny on the high side. LOL

Lesson learned - aftermarket advertised parts said to work or to be for your Pontiac may not be for your Pontiac because many of the sellers are just that, sellers and not Pontiac people, let alone actually work on cars. So it is up to you to check and confirm everything - which can be harder when the previous owner has installed non-Pontiac or generic "said to fit" parts and you don't know the difference between factory and aftermarket because you did not start with factory parts that could be used for comparison.

So start from the beginning and go throw the entire set-up from clutch pedal to linkages to clutch fork to the clutch set-up.

I'll spare you about the oil pump problem that took out my previous 400CI build and caused me to get wrapped up in my long term resto-mod 2.0 car rebuild - which I hope to get done before I die. LOL

[johnta1]

The heads or even the block don't matter on the clutch setup.
(as long as it has the mounting hole for the clutch shaft stud)

The clutch will require the input spline count of the tranny.
Hopefully it has a factory bellhousing.
(I would think the throwout arm pivot would be OK)

And you need the size of the disc/pressure plate to match the flywheel bolt pattern size. (10.5" or 11" usually)

The throwout bearing needs to match for the pressure plate to be used.
Usually a 'kit' has the proper bearing for use with the pressure plate.

Not all that complicated but can have some mis-matches that will cause some problems.

[RJB68GTO]

Thanks for the info John I agree the heads and block should not make a difference as long as they are matched to the engine and all within the same year span. Looks like we have id'ed the problem looks like it is related to the release bearing and clutch fork may have come apart/worn and not allowing the correct length of throw to engage the clutch just something did not look and feel right from a quick glace while the car was jacked up enough to at least see that area. We will be putting it up on a lift later this week at which time we will check all that out and while we're at it we will be installing a new clutch kit. I purchased a RAM #88760 Premium Clutch Kit rated to 20% over base HP or about 440 HP. The guys at Summit were very helpful and through our discussion got me to this clutch from the lighter ZOOM and LUK kits that were only rated for base HP and I know I'm above that, so here's hoping. The release bearing comes with the kit but we will have to deal with the Pilot bearing from a local parts store if needed but should not be a problem. Also I have a new clutch fork so we will not be dealing with any wear problems with the one that is in now.

Optimistic that this should resolve my problems. All we have to do now is get the car to the shop with out a clutch, also not a problem I know from experience that the car can be shifted without a clutch just by matching the revs a little tricky but doable, use to drag in my younger stupider days with out using the clutch never missed a gear, oops did I admit to that. hahaha.

Again thanks for all the help all you guys are great, learned a lot. Keep the greasy side down and between the lines.

Pontiac for ever.

Originally Posted by johnta1

The heads or even the block don't matter on the clutch setup.
(as long as it has the mounting hole for the clutch shaft stud)

The clutch will require the input spline count of the tranny.
Hopefully it has a factory bellhousing.
(I would think the throwout arm pivot would be OK)

And you need the size of the disc/pressure plate to match the flywheel bolt pattern size. (10.5" or 11" usually)

The throwout bearing needs to match for the pressure plate to be used.
Usually a 'kit' has the proper bearing for use with the pressure plate.

Not all that complicated but can have some mis-matches that will cause some problems.

[RJB68GTO]

Hi guys, thought those of you who chimed in on my original post concerning my "Clutch problems noise and chatter" would like to know how things turned out. After we finally narrowed the problem done to clutch as opposed to transmission, thank god for small favors, I went to Summit and purchased a new RAM Performance Clutch Kit #88760 and new linkage springs and fork from Ames Performance. We finally got the car up and tore out the old clutch to find a broken torsion spring on the disc and part of the retaining clip in the fork that holds the throw out bearing in place broke and the spring was rolling around inside the pressure plate. No wonder it would not shift down and squealed. That was bad enough but then we looked further into why all the chatter even on a new clutch that we put in 3 years ago and found that one of the alignment pins for the bell housing on the back of the block was bent, don't ask have no idea so much for buying a car from not so scrupulous dealers. Anyway my guys, who are the best in my opinion at figuring out problems and getting them fix removed the factory pins, aligned the bell housing to the crank and once fitted properly re-drilled new alignment pins so everything was properly in alignment and running smooth and balanced. We installed the new kit, some new linkage springs, a new fork and adjusted the peddle and what a difference. No, none, natta chatter or noise the car runs like almost new again. Actually had to learn how to drive it all over again and not have to compensate for the chatter buy over revving the engine just to get it to not rattle and chatter. It has been a treat to be able to just drive the car the way it was intended again without worrying if I would get it home again.

Anyway thanks for all the help and look forward to hearing about all the Pontiac news in the future.

Bob