Transmission Clunk- Not Normal

[Catalina455]

This morning while driving to work the transmission made an audible clunking noise on decelerration into 1st gear. It happened while the trans was both hot and cold (drove 25 miles on interstate to work). It wasn't a normal noise that the Allison makes as the truck has 19k miles on it. The trans fluid is at the correct level and the filter was changed at 10k miles. In addition, the engine has never been "chipped", and the tow miles are low. Does anyone have any ideas or experienced a similiar situation.

[boilerdude]

just had my 2001 d/m in for the same reason.
they had to reprogram the trans. cumputor.
they said at the dealership that my trans. lost it's program

[JimWilson]

"Lost it's program"? If that were the case it wouldn't shift at all. I wonder what really happened.

[blakmax]

I think its called, join the allison "WORLD CLUB" I personally rebuild world transmissions from Allison and have had so many gliches in my career that i have found that time and service information letters (sil) are the abnormal.My truck has been hitting hard out of the garage since new! Because our Chevrolet Dealers haven't experienced our problems, we as owners are field testing there products! My opinion. Don't get me wrong, I love this truck more than my wife "yuk" but sometimes i am tired of a product in 2003 that acts poorly when i am driving, but drives perfectly when at the hands of a GM tech! Sorry i am venting my problems on this page!! :mad:

[Buckman]

Catalina455,

Was the clunk you mentioned during deceleration immediately after you let off of the throttle or when the transmission downshifted from 2nd to 1st? There have been several threads on this forum over the past months regarding various noises, clunks included. Some of the noises have been generated by items other than the trans, such as driveshaft/U-joints, differential, and transfer case. I couldn't agree more with tim tapper regarding the level of expertise at some of the dealers. On the other hand, I do believe that some of the dealers are striving to become more knowledgeable of how to properly identify and repair problems on our trucks. Again, you can't judge all by the actions/abilities of one.

If you can provide any further details about the problem with your truck, perhaps the forum members can help.

[Catalina455]

Buckman, the clunk occurs on the 2 to 1 downshift, but is not immediately after letting off of the throttle. Since I have an excellent relationship with my dealer, I will have the service manager take a quick look at it when I go in later this week to pick up some parts that I have ordered for my 70 Cat Sw.
Thanks,
Randy