The Stovebolt Site Forums The Shop Area Driveline clutch chatter?

I've noticed that my one ton sometimes bucks when I'm letting out the clutch. It only happens when I'm starting from rest going uphill in second gear. It's not really chattering, and it doesn't last long, just the first few seconds until I get moving. Is this normal? I realize that it takes some force to get this thing moving, especially with the big tires (7.50/17). Should I be starting out in first gear? I hardly ever use first, it's so low in the SM420.

I have no problems in any other gear once it's moving, and I have no problems on the flat. But even a slight rise, like coming out of a parking lot, causes the bucking.

Any hints, suggestions, advice?

Tim

Higher rpm’s and more clutch slip will be your friend in such situations.🛠

I think if it was me, Id pull on in 1st on hills. Id rather have an extra shift to get moving instead of causing premature clutch wear. 2nd on the flats is fine otherwise. Sounds like you might already have a clutch wear issue. Monitor it. It will only get worse, sooner or later.

Check your motor mounts for looseness. Just a little bounce, especially at the bellhousing, will cause that kind of symptom. The clutch linkage gets to moving back and forth as the bellhousing bounces, and it becomes a harmonic vibration that feeds on itself.
Jerry

Yep, in the SM420, true 1st gear would be "granny" or "compound low." That's my parking brake. When I take off in it, I will slow to a stop before I can shift into true 2nd. Uphill would be worse. So true 2nd is my 1st, effectively.

For me, I'd try to use the gas pedal and clutch pedal to figure out how to minimize the buck. Right foot, left foot getting on the same page might solve the problem.

Well, I'm hoping it's not the clutch wearing out. It has 71 miles on it now. And the motor mounts front and rear are brand new. I was worried that I might have some oil or grease on the clutch, but I see no evidence of that. I was worried that I might not have gotten the rear main seal right (the infamous rope seal), but there is no oil leakage apparent. I guess I just need to get used to driving this thing again.

Tim

Maybe the clutch just needs to break in.

I always start in 1st gear, but my axle has highway gears.

Tim, X2 on Jerry's advice to check motor mounts. Tightening them up solved my problem. Even though they are new in your case, won't take long to check to see they're still tight and it would be the easy solution. Well, the easiest thing would be to intentionally slip the clutch and see if that helps. While in high gear at a 30 or so mph and going up hill just ride the clutch a bit causing it to slip. Not for too long, just enough to burn off any oils. May help and if not overdone won't hurt since few will ever drive there trucks to the point of actually wearing out a clutch.

Good Luck,

RonR

We had a '51 Chevy car when we lived in Seattle in the 1960's. The hills downtown were so steep that at a stop light, I used the parking brake and released it as I let out the clutch. Otherwise, I'd probably roll back into the car behind me.

Also, "heel and toeing" with the right foot worked. Let up the brake with the heel while giving it more gas with the toes.

Are you rolling backwards at all?

Pictures of the '51 are in the link in my signature.

The jackhole who built my truck forgot to tighten the rear motor mounts. I would have fired him but I am a one man shop...
He talks to himself incessantly, yet never seems to listen to himself.
Carl

I'd still fire him!

I work for the same guy. He insists hes always right and refuses to admit when hes wrong. lol.