Shuddering clutch engagement.

[Mike F.]

Not exactly sure how to explain this, but here goes. I have a 70 L-46 (350/350) with M-21 4sp installed. Engine was rebuilt last winter, when I installed it I also installed a new clutch assembly. The clutch is adjusted per the AIM, engages/dis-engages/free play at top of pedal etc..

With the car stopped, transmission in 1st gear, as I let out the clutch to start moving forward (revs 1000-1500) I get a very noticeable shuddering throughout the drive train (No matter how much I try to feather the clutch). The engine is not dying or loading up, I just can't seem to get a smooth launch unless I bring the revs way up (2000rpm or higher). Once the car is moving everything shifts and moves as normal. I didn't have this shuddering prior to the rebuild/clutch replacement.

I can pull the tranny and clutch back out, but what am I looking for that's causing this problem?

TIA,
Mike

[Terry D.]

Re: Shuddering clutch engagement.

Was the old flywheel used? Did you have anything done to it? How many miles on it? Whose clutch assembly did you put in? Terry

[Gene M.]

Re: Shuddering clutch engagement.

What brand, model, (hope it's not china made) clutch and pressure plate did you install? Is the pilot bushing new, good? Was flywheel surfaced?

[Mike F.]

Re: Shuddering clutch engagement.

Flywheel, if original could have up to 95K miles on it. The machine shop said the flywheel looked fine and "just cleaned it up a bit". Without digging through the paperwork or calling them, I don't know if that means removing .001 thousandths or scotchbright.

The clutch/pressure plate? I'll have to find the boxes. IIRC I got it from either NAPA or Carquest. Pilot bushing was new.

[Edward J.]

Re: Shuddering clutch engagement.

Mike, I have done many clutch jobs over the years and chattering is generally caused by the flywheel of pressure plate. there's a chance the machine shop may have not had the flywheel mounted squarely on lathe. In any event your likely not going to fix the problem without redoing the job. My advice is to take the clutch back and let the parts store replace it under warrenty and bring a copy of the machine shop bill stating the flywheel was machined. and have someone else redo the flywheel. There is a lot of machine shops with older equipment that has not been cared for or kept up. One last thing on the quality of clutches, it seems that most are made in China today. there getting better but there are some that are not so good. Luk clutches are one of the better manufactures.

[Terry D.]

Re: Shuddering clutch engagement.

I agree with Ed, I've had a Luk in my 62 with a 383 crate motor for 4 years now and no problems and last I looked they are made in the good old USA. The only thing I would suggest is a new flywheel, not that expensive and 43 years newer. Terry

[Joseph M.]

Re: Shuddering clutch engagement.

Just went through the exact same problem with my 67. Turned out it was a poorly cut flywheel. You probably need to redo the whole assembly with new parts. If you don't replace the flywheel just make sure the machine shop resurfacing your old one knows what they're doing. Also, consider a Luk clutch and pressure plate.

[John H.]

Re: Shuddering clutch engagement.

Also check out your transmission mount rubber cushion - when they deteriorate, they can create the same type of shudder at initial engagement.

[Mike F.]

Re: Shuddering clutch engagement.

Thanks for all the help!

[Robert K.]

Re: Shuddering clutch engagement.

I'm surprised to hear about re-surfacing a flywheel on a lathe. I thought they had to be ground because of hot spots in the face of the flywheel. 'Em I wrong?

[Jack H.]

Re: Shuddering clutch engagement.

I'm surprised to hear about re-surfacing a flywheel on a lathe. I thought they had to be ground because of hot spots in the face of the flywheel. 'Em I wrong?

Every flywheel I've ever had resurfaced had swirl marks on it indicating a grinding/polishing operation. I've never seen one with rings or concentric circles like you'd see with a lathe operation. Maybe just poor choice of words on poster's part?

[Edward J.]

Re: Shuddering clutch engagement.

Jack you hit the head on the nail. I had lathe on my mine,

[John H.]

Re: Shuddering clutch engagement.

I'm surprised to hear about re-surfacing a flywheel on a lathe. I thought they had to be ground because of hot spots in the face of the flywheel. 'Em I wrong?

Correct flywheel surface finish results from orbital grinding, not a lathe operation; should look like the photo below.


FlywheelFinish700.jpg