The Stovebolt Site Forums The Shop Area Engine Shop Clutch chatter

A couple months ago I posted a thread about violent clutch chatter when starting in first from a dead stop. Readers made several recommendations including new rear motor mounts, new pressure plate, and oil on the flywheel. I have not done any of the recommended repairs, but I mentioned the problem to my NAPA guys today, and they immediately said "flywheel". My flywheel has been re-surfaced twice, and the shop never mentioned that anything was wrong with it. I am reluctant to replace several components when I feel confident that the problem is just one thing. What do you guys think about a bum flywheel?

I don't think it's likely unless it happened immediately after install. How old is your clutch? Chatter is usually when the clutch has oil on it or is nearly worn out or the pressure plate is weak. I don't know about the motor mount theory, but it could happen. You aren't going to find any answers until you tear into it in any event.

A worn or missing bronze pilot bushing in the end of the crank can result in chatter/judder.

If it's not oil from the 2 piece rear seal, I'd check for runout at the flywheel. With what info you've offered it's tough to pinpoint whether there was chatter since a rebuild....or that it just started recently.

Motor mounts can be visually checked and if you changed the seal in the front pilot bearing retainer shaft before bolting up the T5, you should be able to eliminate that as a source of oil.

Looks to me like it's going to be necessary to pop the engine/transmission in most any case if you've eliminated the "usual suspects."

Dave

change the pressure plate, you had not done that.

Most likely it is a weak pressure plate assembly (the springs) although it IS POSSIBLE for a flywheel to cause clutch shuddering / chatter if the face of the flywheel is not machined flat or it has been machined down beyond reasonable limits. The more material that has been removed during machining, the less efficient the clutch assembly will be especially under loads. In any case, I would recommend a complete inspection of all components, chatter soon overheats the clutch disk and glazes both the face of the pressure plate and the flywheel surface. Glazing then = more slippage and chatter.

I have a 57 V8 original stock position front motor mounts and even after resurface , pressure plate, bearing, seal, clutch it still chatters in 1st gear 1 out of 3 times. It seems to get the engine jumping on the front mounts. My mechanic recommended side mounts. He happens to have a 55 tow truck.

When mine chatters like when going up my steep driveway from a dead stop to put it In first, I can stop and try it again or slip it more and it will do better the second time. Most of the time if I start slow with little throttle and get the clutch pedal out without slipping much it avoids the chatter. 2nd and 3rd are fine. In first it seems that I jave to try to keep the engine from rocking. My mounts have all been replaced.

not the fault of front mounts wilbur, they work fine, more likely the operator than anything, and after a few dozen times of the chattering starts, the clutch disc can get 'marked' so it's more likely to happen more often - but as above, it could be an uneven pressure plate or flywheel, or fine checks/ cracks in the flywheel that have gummed up

Bill

How about the backside of the Presure plate? My machinist resurfaced same and it solved my prob. This is the surface that bolts to the crankshaft, both must be paralel and true to the crank.
dg

Well maybe it was installed poorly but I it had it replaced because it chattered and after they were done it still chattered, not quite as bad or as often but it does it. It only has like 8 to 10 hours of drive time on it since that all was replaced. Maybe 250 miles total.

This is my 13th vehicle with a clutch and only had this issue with one other vehicle and that was because the mechanic that changed the clutch after it was warn out did not replace the leaky rear seal and it leaked oil that within a couple days got onto the clutch. He had to replace it all again on his dime.

I do not think that this current case is a result of my driving style. I also have a 1997 chevy Z28 with 145,000 miles on it and it is still on the original clutch and I raced it in SCCA autocross for 4 seasons. I think my clutch technique is OK. I have been driving sticks for 39 years.

When it chatters the whole truck cab jumps around pretty violently. I should propably recheck all the mounts to make sure one is not broken or loose. The front two have some new rubber on them, maybe they have compressed or the mount bolt may have broken. Or the rear transmition mount may be loose or disconnected if the mechanic did not tighten it back up after doing the job. I need to check that.

not dissing your driving wilbur, but a mid 50s truck isn't mid 90s tech, and it's sure not a race car if the chattering is so bad the cab jumps about, it's your fault for not immediately jamming in the clutch and trying a new approach .... I know that my truck can chatter sometimes, especially cold, when I don't "pay attention", if I either keep the engine almost at idle or rev it a bit more and/or slip the clutch a bit it's fine - also once well warmed up it's not likely to happen, who knows why? when the clutch is worn out it'll get looked at, could have any of the problems folks mentioned above [but milder]

it may be that the mount position has some influence [it is a 4 point mount tho with the bellhouse mounts], but I've never been into trying to improve the original design of an old truck to avoid learning to deal with it, many thousands of drivers have put many millions of miles on old trucks without modifying the technology

add: "rear transmission mount"?? I hope you mean bellhousing mounts, and don't have the car trans with a mount on it - a 5 point mounting setup could be a problem, or no bellhouse mounts so a 3 point, ditto

Bill

Red58, No offense taken. I just did not want you to think I was a 20 something kid that liked trucks and did not know how to drive.

It jumps and I have to retry. Sounds like it happens to you once in a while maybe it is just the way it is. But I think there is more to it than that.

I just took a look at the motor mounts. I have the two front ones in stock V8 location and the two off the bell housing area (not transmission, I have not looked at them in the last 18 years ) that are just big rubber blocks with a bolt and washer thru them. Those rear ones have different bolts in them. One side is a bigger bolt head and had two washers under it of different sizes. The other side has a smaller head and a metal rectangular plate on it. The rubber looks good. I believe I replaced them about 20 years ago. I will have to start keeping a better log of replaced parts. But at that time one was missing a bolt so I found a replacement bolt but should have changed them both out to be the same I guess.

The front mounts I replaced the rubber on about 3 years ago. At the time they looked the same when I got done. But looking at them now the drivers side larger motor mount cushon that sits on the top of the lower L bracket is thick and the one on the passenger side is thin. The parts catalog shows them both as thin and the outer most top and bottom are smaller but thicker, those look normal. But I am concerned that the drivers one is thick. That would make the motor be uneavenly mounted and could cause it to pivit on that mount since it would be higher/taller than the passenger side.

I guess I should buy some more cushions from classic parts. Maybe get some new rear mounts as well. I see they have some Polyurethane rears with plates on them that look good.

That may help my chatter and jumping cab issue.

Is it normal that they would wear/compress that way? Is that just from the engine torque? Or should they always look the same size on each side?

torque may result in them compressing different, but if they're both equally tight, I'd expect the only thing that would cause the difference [assuming they started out the same] is oil saturation, which can deteriorate rubber ... the rear mounts need that plate under the bolt [U shape if I remember right], it's a 2 piece deal - I'd get new, but original rubber, the poly ones squeek in time ... it could be a combination of front and back giving an uneven stance to the driveline, affecting the front U joint

Bill

As I stated, be sure that ALL surfaces mounted to the crank are parallel, If not, then the flywheel/clutch will not be no matter what. But, it's yer truck bro.
dg

I had a chattering problem , turned out some of the bell housing bolts had worked themselves loose . Tightened them and problem went away .

I have a chattering problem at the moment due to contamination of the clutch plate. When I get the oil leak fixed I will put in a new disc. I find that parking it with the clutch held in with a piece of wood, seems to dry it out some.

My chatter can be quite violent and I think this is due to the harsh suspension in the back. In my case if I slip it more it makes the problem much worse. My method is to get it slightly rolling and then let off the gas, let out the clutch and then give her gas. On a hill I have to use bull low.

I was just wondering.... Why is the chatter worse when I am in 1st gear and starting out then if I do it in 2nd gear?

Seems like I would have to be slipping it more to start in 2nd gear?

Do you think it might be more an issue with slop in the U joints and backlash of something?

Just an old farmer here, but you might try putting it in high gear, revving the living hell out of it and slowly engaging the clutch. My father taught me this technique and it has worked on several vehicles, including a semi tractor. I would not guarantee success, but it might be worth trying.