Clunk In Reverse When Hot ?

[Scott Lombard, IL]

I have a '01 2500HD D/A CC/SB with about 12K miles on it. Vin# 1GCHK23101F152842. I have recently had a intermitent problem that only occurs when the trans temp reaches almost 200 degrees.

On warm days when towing (anything, even a little trailer under 3K Lbs)when I back the trailer into the spot the driveline has two distinct engagements into reverse.

When I put it into reverse and leave my foot on the brake for 2 - 3 seconds I feel it engage reverse, then 2-3 seconds later it "clunks" or feels like it is going into reverse again ? I don't touch the throttle and I've recreated it without the trailer when the trans was already hot. I thought it could have been the electric brakes on the trailer engaging. One time recently I came to a stoplight with a trailer on, and about 2-3 seconds after coming to a complete stop it felt like someone very lightly rearended me ?

I have read the other posts referencing a driveline "clunk" but they seem to be under different circumstances.

Does anyone know of a good Duramax mechanic in the Chicago / Western Suburbs area ? The dealers I've tried seem to know less about the TSB's and vehicle issues than I do.

Thanks for any help or assistance that is offered! :confused:

[DmaxMaverick]

Scott

Welcome to The DP!

If you haven't already, replace the spin on tranny filter. Many, including me, have noticed the filter needs to be changed soon when the truck is new. You shouldn't go past 5K without a new filter, and even sooner if you tow. Don't forget the magnet! As soon as you pick up the new filter, write "MAGNET" on every side of the box, and the filter (I stole that idea smile.gif )

If that's not it, good luck finding a good shop. Cheers.

[JimWilson]

Do you have the locking read diff? That might be the cause. I don't have the D/A combo, only the 6 liter/4 speed with the locker, but I've noticed that myself. AAMOF, this morning I was sitting at a traffic light and it happened. When it turned green I put my foot on the gas and nothing happened for almost a second. The engine noise increased, but I didn't move. Then when I did start to move there was a clunk from the rear that made me look in the mirror to see if I had gotten bumped.

[Buckman]

Scott, For starters you should read the thread on New calibrations and "Trussman's Syndrom". Have you had calibration updates done and if so, how recently? There have been updates to address various problems such as a delayed 2-1 downshift at a stop. It is imperative that both the engine and transmission get the latest updates to realize the full benefit and improvements. Keep us posted at to the outcome of your quest to find a good dealer in your area. I'm sure that many others would appreciate knowing where to go for good service around Chicago. smile.gif

Buckman

[Scott Lombard, IL]

Thanks a lot for the quick responses. I appreciate it very much.

I have an appointment to get the filter on the trans changed. Last time I took it in and requested it be done the dealer didn't have ANY of the parts needed to do the trans service? They just sent a card saying they now have the parts.

I was reluctant to have the reflashes done due to the conflicting reports of good and bad on this site about the reflashes...

Can anyone tell me which ones I should have done based on my specific vehicle ? I have never had any reflashes done. Are there any I should specifically NOT have done?

THANKS again for all of your assistance. It is appreciated.