Mopar_Mudder

Everyone will be glad to here that this in not about the 2000 rpm vibration that alot of people are having, my truck never has produced that vibration.

But all of the sudden I do have a, what feels like, drive line vibration when you let of the go pedal. Kinda feels like you are running over the rumble strips on the side of the road reaallly fast. You have to play with the peadal to make it do it some times and if you aren't driving it I don't know if you would notice it.

Went under the truck and checked things out and the center drive line carrier bearing seems maybe like thier is a lot of slop in the rubbers. Also I have always had a little oil on the under side of the truck at the rear of the transfer case, their seems to be getting to be a bit more now and it has a little slop up and down in the bearing. But the front drive shaft has the same slop in it for that mater.

Just wondering if anyone else had this before I take it in to get looked at, hoping it gets a little worse so it is easier for them to feel and find.

bulabula

No, can't say I have any vib's like that, but am interested.

Is it only during decel? and in 6th; or in other gears? Oil level ok in the Xfer case? I've only had a "very" slight weep from the PTO cover on the tranny (a damp spot), otherwise everything else under mine is dry.

Mopar_Mudder

It is not related to any gear. It does it at any speed but the pitch of the vibration goes up and down with the speed you are traveling. It really only does it the most when you are inbetween the accel and decelaration. Hold the pedal just right so the drive line is keeping up with the speed of the truck, worse when coasting down hill. Feels like a bad u-joint but none of the clicking and snapping noise you normally get with a bad joint, and the joints are tight. Does it with clutch in or out.

bulabula

If your U-joints are ok, could your driveshaft yoke(s) be worn?

This reminds me of a number of years ago when I used to play with Mustangs. And guys would swap out 3.08s for shorter gears; and it seemed like that when 4.10s were installed (notably in higher mileage cars), they often developed vibs either due to the driveshaft not being properly balanced for the higher rpms, or the driveshaft yoke in the transmission was worn unacceptably causing a vib similar to what you're describing. And it would seem to happen most often when the drivetrain was floating.

Maybe its that slop you're feeling when you're pulling it up and down.

Mopar_Mudder

Yokes them selfves are tight yes. Seems the rear bearing is getting slop in the back of the trasfer case. Same bearing I have replaced in the back of the NP205 case in my 83 1 Ton actually, but that goes bad for another reason

msatow

The TSB is not ready yet. The company doing the testing is American Axle MFG 800-299-2953. The vibration is coming from normal diesel harmonics and the transfer case exciteing the rear driveshaft. The trucks come with a 85 Megahertz dampner with a 34 spline slipe yoke on the driveshaft. The fix for the vibration is belived to be a 385 Megahertz dampner with 34 splines. AAM wanted the 385 dampner on the truck at production, DC went with the small one. The slow down is this, their is no part number on the shelf for a 385 MGH 34 spline dampner. How long, who knows. I think thay need our help. Remember the squeeky wheel gets the grease. Call !!!!!!!!!!! ASAP!!!!!!!!!!