I am tracking down a bad shudder on take off (dead stop). If I am rolling even a little bit it won't do it. If I haven't driven the truck in several weeks it won't do it the first half dozen starts. It does it very violently when slipping the clutch in reverse.

I replaced the u-joints a while back and the carrier bearing recently. I replaced the clutch and rear main seal awhile back as well. Random, and I'm not sure if related - one of the bell housing to block bolts was found backed out the last time I had it on the lift.

The best thoughts from local friends are either the pilot bearing is gone, letting the clutch disk wobble as it engages or excessive axle wrap from a broken leaf spring. Any good ideas out there?

 

Did the shuddering happen after the U-joint and carrier bearing replacement?

Did all the U-joints in the driveshaft rotate smoothly after they where installed?

Did you change the mounting height of the carrier bearing in anyway?

Broken transmission mount, which happens more that most people realize?

 

Thanks for getting back to me - responses are in blue in the quote.

 

did you align the drive-shaft? the yokes have to be aligned or the truck will bump and thump all over the place..

 

I am not sure how you align a drive shaft. Am I simply looking for the u-joints to be "opposite" each other? My problem is strictly on take off - at any speed after the clutch is let out there is no bucking or jerking. Would alignment do that?

 

As far as checking a busted transmission mount… Y
You should be able to put a block of wood on a floor jack under the rear of the trans. and see if the mount has separated from the rubber and metal when you get some of the weight off it.

 

Some good and some bad news : yes the trans mount was thrashed and came off in two pieces, we put on a different one (not positive it was new, but it was not separated) , and it appeared fixed. less than 60 miles later and it is back to doing the same bucking/shuddering. No broken leaf springs, the drive shaft is keyed so that it cannot be reassembled "off". We poked a fiber-optic camera in where the clutch slave cylinder goes in and saw nothing out of line. I am going to revisit the trans mount tonight and see what's up. Any other places to look before pulling the trans?

 

What type of clutch is in it? Im running a kevlar/ceramic button and used to have a full ceramic button and they both rattle the truck pretty good unless you give it some more throttle, or just dump the clutch out quicker. As my rear springs have sagged over the years, axle wrap has gotten worse, amplifying this.

Fwiw my 2 piece driveshaft is keyed 180° apart, so it can go back together 2 ways. Shouldn't affect anything until higher speeds if its out though.

 

The trans mount was/is new. The clutch was replaced with another southbend. 13125OK-HD I think. 13 inch clutch without replacing the input shaft at any rate, came with a new flywheel and the roller bearing pilot. The clutch that was removed showed a really funny wear pattern on the fingers where the throwout bearing touched them. Better that 3/4 of the fingers had what the mechanic considered "normal" wear. The contact patch was round, smooth, and consistent. The remainder, all in one section, didn't look like they had been worn at all. The mechanic said that could easily explain the jerky engagement but had no good idea what would cause the problem to begin with.