Hello all. I have driven my Father-In-Law's 2004 GMC 2500 HD CC 2 wheel drive with the Duramax/Allison engine and transmission. When I come to a stop and then go to accelerate, there is a "thump" and it feels like it is either in the transmission or in the driveline somewhere. If I come to a stop and pull up just a little, the thump occurs and when I take off, the acceleration is smooth. Any ideas what this may be? The truck has 1,300 miles on it. In my opinion, the truck is awesome. The power is great and it drives like a dream. Wish I had the $ to buy one myself. Thanks for any help or ideas concerning this.

I had this on my 2000 1500. It was a common problem with the yoke at the end of the drive shaft was not right (rear end). The 1st fix was the good 'ol grease the splines. Then they came out with a nickle plated yoke that cured the problem.

Thanks for your reply Mike330R. I'll have to look on this forum for info on how to grease the splines. Anyone else had this issue?

Pull the drive shafts and grease the center slip yoke/spline make sure you mark the spline/yoke and put back in same position I used plastic zip ties to hold the rubber boot.I did this on mine and it is like a different truck now.before no matter how easy I was with the throttle I got the thud.

Thanks compressor59. What type/brand of grease do you use? I have never pulled the drive shaft on anything before. Is it very difficult? I have done lots of things to cars but never anything involving the driveshaft. Thanks again for the reply.

I had a chance to work on my wife’s truck this week end. I greased the drive shaft spline as compressor59 suggested. I unbolted the rear u-joint. I got to looking at the clamp holding the boot and found one little ear holding it together. I took a small screw driver and bent the ear up then slipped the screw driver under the edge of the clamp and it just popped right off. When I got the shaft out, the spline was not dry but it did not have much grease in it. I added a goodly amount of wheel bearing grease and slid it back together. I took the clamp and found that it had a “crimp” point on it. I placed one side of the clamp in a vice and got hold of the other side with a pair of Vice Grips and gave it a good pull. The crimp straightened out a little. I put the clamp back around the boot and held a screw driver on the ear while my son tapped it down with a small hammer. I then took a pair of “end” (wire) cutters and gently squeezed the crimp to tighten up the clamp. It did not go back quite as tight as it was originally but I think it will hold. I will check it from time to time.

I got to thinking about clamping a rotating boot like that. compressor59 said that he used a wire tie to put it back together. I was thinking of using a hose clamp but was afraid that the weight of the screw on one side would unbalance the drive shaft. Well then I thought about using several small hose clamps, like you would use on a fuel line or a small air hose. If you used several, 3 or 4, however many it took to go around the boot, and if you spaced the screws evenly around the boot, it would balance out and you should have no vibration. I have heard of using large hose clamps to balance drive shafts.

As you can tell, I more or less have a “factory looking” repair. This brings up another point. I have an extended no deductible factory warranty on this truck. I called the dealership where I have been having warranty work done and talked to them about this “repair”. They said that “lubrication” was not covered under the warranty. They also said that if I went in there and messed with the drive shaft splines, I would void my warranty for that part. That is why I a

Are you sure it's not the little car in front of you that you went over.http://www.dieselplace.com/forum/smileys/HiHi.gif

Well, my Father In Law took his 2500hd cc 2wd to the dealer to fix the "thump". They said that condition was normal and that there was no spline to grease with the Allison Transmission. I guess I'll be doing the greasing myself when I get some time. http://www.dieselplace.com/forum/smileys/Disapprove.gif

The dealer is correct. There is no spline with the Allison. The spline is behind the center support bearing on the rear drive shaft section.

Oh. OK. I had in my mind it was on the tranny. Thanks for setting me straight.http://www.dieselplace.com/forum/smileys/Approve.gif