[Not a Y88 T/A]

My 1978 T/A with a Borg Warner 4 speed shakes violently when letting the clutch out from a dead stop. I can avoid this by slipping the clutch excessively as the car begins to move.
I have replaced the clutch disc, pressure plate, throw out bearing, pilot bushing and transmission mount and it did not fix the problem.
Any ideas on what is causing this and repair suggestions is greatly appreciated.

[Chief of the 60's]

Did you use good parts or cRock Auto/Big Box Store parts? There is a difference.

Also, did you make certain the flywheel was seated properly to the crank? Did you clean the new flywheel surface?

[Not a Y88 T/A]

Back when the shuddering started, the car had a Center Force clutch in it and a Hays flywheel. I replaced the clutch with a Zoom kit from Summit and I cleaned up the Hays flywheel. The flywheel only has about 500 miles on it.
Yes, I did make sure that the flywheel was seated properly to the crank.

[track73]

How are your motor mounts?

[steve25]

Did this symptom creep in over time with the old parts , or all of a sudden show up?

Does it do the same if you start off in 2nd gear, or is it worse?

Where do you live and how does the motor start when cold, as it always has?

Does the motor when warm idle higher then normal like it might have a Vacuum leak?

Also installing new parts without getting the flywheel resurfaced could be the root cause of your whole issue now with the new parts!

[Chief of the 60's]

Originally Posted by Not a Y88 T/A

Back when the shuddering started, the car had a Center Force clutch in it and a Hays flywheel. I replaced the clutch with a Zoom kit from Summit and I cleaned up the Hays flywheel. The flywheel only has about 500 miles on it.
Yes, I did make sure that the flywheel was seated properly to the crank.

If the parts had only 500 miles on them then why did you replace the clutch disc?

[i82much]

engine mount? try jacking under the oil pan with a block of wood and see if it is separating.

i have had exactly the symptom you describe from a broken engine mount.

[Not a Y88 T/A]

The motor mounts are good.

The shuddering started all of a sudden, but has gotten much worse.

I'm not sure about the shuddering with a second gear start, I will have to try it next time I have the car out.

The motor starts and runs fine whether warm or cold.

Here is why I replaced the clutch. Years ago ( probably 16 or 17 years ago) I built a 455 for the T/A and had my 400 flywheel center bored out for the bigger 455 crankshaft. When I put the 455 in I also bought a new Center Force clutch kit. 5 or 6 years ago, I put the original 400 back in and had to buy a new flywheel because the center was bored out on the original for the 455. I bought a Hays flywheel and reused the Center Force clutch, pressure plate and throw out bearing. I drive the car very seldom. About a year and a half ago
the car shuddered for the first time and it has become worse as time went on. I thought it may possibly be the clutch and a few other people I talked to said the same thing. One friend of mine said he knew someone in the past that had a very similar problem and it kept getting worse until he changed the clutch, which fixed it. Changing the clutch has not made my car any better, it is still just as bad if not worse.

[nmoreilly]

Seems to come up with "high performance" clutches and flywheels. I have a McLeod super street clutch / Hays 13-130 flywheel behind the 469 In the 69 GTO and I get a shudder sometimes in both directions from a gentle start. I never get any chatter with this combo though

[Chief of the 60's]

If you had the chatter before, a new disc generally won't fix the problem without turning the flywheel. A clutch is not much different than a disc brake setup. If your brake pedal has a pulsation, new pads won't make the pulsation go away. This is why I asked.

Sounds like the cure now is, another new clutch disc, resurface the flywheel, new pilot bushing and maybe a new throw-out bearing.

[Not a Y88 T/A]

I cleaned the flywheel up with 3M discs on a cordless drill. The 3M package says "great for gasket removal, brake disc finishing and metal polishing".

I did not see any discoloration or hard spots on the flywheel after cleaning it up.

[i82much]

two thoughts:

organic discs chatter far less than semi-metallic.

oil leak onto flywheel?

[Not a Y88 T/A]

I thought maybe oil as well, but everything was dry when I took it apart.

I'm not even sure if either the clutch I took out or the replacement are organic or semi-metallic.

As I mentioned earlier, the old clutch was used behind the 455 before I put the 400 back in and it didn't chatter then or for several years with the 400.

The shudder has gotten so bad that the whole car feels like it is going to shake apart.

[gtohunter]

I've run into issues with flywheels developing "hard spots"...areas where its gotten super hot and you can grind to clean up and true the surface, but in short order the softer material will wear slightly causing high and low surfaces. If turning the engine with a dial indicator on the friction surface of the flywheel you might find a little deviation that would indicate high and low areas. Additionally close inspection might reveal light heat checking?

[Dick Boneske]

I have a similar chattering problem with my '64 GTO. Clutch chatters badly only when the engine is hot. At startup, forward and revers are smooth as normal. This has been going on for five years.

[tooski]

Bellhousing alignment? I've read a couple of threads regarding this, but not sure if a misalignment would cause shuddering/chattering.

[steve25]

I hate to say this, but it would not be the first time that a crankshaft was completely cracked in half thru a main journal, yet out of gear or once above a certain rpm ran mostly fine.

Well ran fine for a while until it gave out completely!

A quick check for such would be to pull out all of the plugs, get under the car and rock the crank back &forth with the flywheel while watching the balancer closely to see that it tracks every little motion of the flywheel.

You can put one hand on the flywheel and one on the balancer and quite easily feel if there’s something wrong,

[chuckies76ta]

Hmmm, Post some pics of your clutch and part # from summit on new clutch. You say: (I'm not even sure if either the clutch I took out or the replacement are organic or semi-metallic.) I'm wondering if you installed a Ceramic Clutch? As was mentioned the bell-housing has to be checked for run out when installed.
Another issue I've had was ARP Pontiac Flywheel bolts. The head of the bolts were sticking out to far making contact with the clutch disc. You probably should have had the Flywheel resurfaced and checked for trueness.

[PontiacJim1959]

Another point. Was the car originally a 4-speed? It is possible that when a swap is made, the rear axle ratio is not changed out and you have highway gearing which takes a lot more clutch slipping to get the car rolling, and clutch chatter can be an end result when you don't slip the clutch enough to get the car rolling.

Check trans mounting points at the rear. Maybe something has let go in that area.

I think the bottom line here is to pull the trans and the clutch set-up and begin anew. Don't wait until you break something.

Have the flywheel surfaced by a machine shop. A drill and scuffy disc isn't going to surface the flywheel evenly and may actually cause unevenness.

Check the height of the flywheel bolt heads as pointed out. I had this experience myself with the Hays flywheel and installed the wrong bolts. The heads protruded above the plate just enough to hit the springs on the clutch disc. Made a strange whine each time I let out the clutch.

Check the pilot bearing/bushing for slop/wear both in the center hole where the input shaft goes and the fit into the crank. Check the slop in the front input shaft to see if the trans front bearing is shot.

Know what friction material you have. There are a number of different options. Some are designed to grab more than slip. The disc could even become warped or damaged. But, I would replace it while out and make sure you select a "floating hub" versus a solid hub, and one that has a "marcel spring" rather than riveted solid together as these are more aimed at racing.

[gtohunter]

Originally Posted by steve25

I hate to say this, but it would not be the first time that a crankshaft was completely cracked in half thru a main journal, yet out of gear or once above a certain rpm ran mostly fine.

S10 2.8...drove it home and no chatter