Strange transmission? clunk

[Stlheadake]

This has happened to me on two separate occasions with similar circumstances. Both times I was driving along at approximately 35-40 MPH and didn't see a stop sign. I jammed the brakes to make the stop. On both experiences there must have been a bump in the road and the rear wheels hopped.

At the same time that the wheels hopped I heard a slight clunk sound, and it felt like either the tranny downshifted or the wheels caught, because the truck really slowed.

I am VERY familar with ABS kicking in, and I am positive that wasn't it. Typically you have the exact opposite feeling with ABS. You feel like you aren't going to stop, not a sudden slow down.

My dad has an 06 CC DA 2500 too and has experienced the same thing. Has anyone else had this experience?

[jbplock]

Could be the driveshaft spline on the Allison output is dry ... if this is the cause greasing the spline fixes the problem ... my 03 makes a clunk occasionally when backing up .. most often after a long trip ... see the following link for more info ..

2003 Duramax Diesel clunk (http://72.22.76.69/tdpforum/showthread.php?t=19546)

a forum search for "spline clunk" will also yield several more threads ...

:)

[madmatt]

My 02' gas engine truck does the same thing. I've pinned it on the rear end bounceing up and a wheel locking up

[Stlheadake]

I agree it is with the rear wheels bouncing. The question is am I breaking something, or should I be concerned? It hasn't done it again since I last posted.

I dunno, I'll just keep driving. I won't worry until there's something to worry about.

[madmatt]

I don't think it's anything to worry about just something thats gonna happen at rough stops.

[cndnls]

I had the same problem, but mine was the carrier bearing for the drive shaft. Also when it got cold the rubber got hard and the problem went away, until the temps went back up..

[Duramax D]

Hi, I had a strange clunking sound coming from what I thought was my rear end while hard breaking or soft breaking while hot. I figured that there was a problem in the drive shaft or rear end but the dealer just reported what seems to be an ongoing problem with their transfer cases. A clip that holds the pump in place will break and rub a tiny hole in the side of the case. After time all the fluid will come out without even noticing a drop on the ground. Once this happens all the grease on the drive shaft splines heats up and drys out. Then comes the clunking sound. Everytime you go over a bump or break the drive shaft is clunking into the transfer case. This may not be your problem but it is worth the check to avoid needing a new transfer case.