Right after putting the truck in reverse and backing up about 10 feet or so, I feel a "bump" from under the truck. It doesn't always happen, but it happens every time I start up and back out of my driveway each morning with a cold engine. The first time it happened I thought I ran over something, but now it feels like something's ready to separate itself from the rest of the truck. Anyone got any ideas? Thanks.


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):h mazda?):h

:funnypost

Mine does this as well, every day when I back into my parking space at work. I have no idea what it is and, of course, the stealer cannot duplicate. Let me know if you figure it out.

Remove the drive shaft, clean the internal splines with spray brake cleaner and lube with your favorite grease. Mobil 1 synthetic has worked long and well for me. Later! Frank

Yo! Mine does the same! I thought I was nuts. I'm gonna watch this thread.

Frank:

I'm not capable of doing what you said, at least not without significant help. Wouldn't this be covered under the 100k powertrain warr.?

No! Our truck only has a five year/100K on the engine and 7 year/200K on the injectors. You are on your own with the rest of the truck. Look around for a small independent shop. Every town has a guy with a good rep and his flat rate will usually be less. I bet one of your work buddies is a good shade tree mechanic. They will usually work for lunch and a six pack. Don't pay the six pack before the job is done. Later! Frank

Frank, thanks for the info. I have to admit that I'm wondering what could have happened to make it necessary to drop a drive shaft on a 500,000 mile truck with only 36,000 miles on it. And, I'm wondering what kind of damage can I do if I just ignore the clunk? That's probably what the dealer will recommend.

I thought that the 100,000 miles covered the engine and drivetrain?

I thought that the 100,000 miles covered the engine and drivetrain?
Nope--100,000 mile warranty only covers the engine and then after the 3 year or 36,000 miles there is a $100.00 deductable for each visit with engine concurs. Full payment required for any other problems. -:t

Well I guess it's about time for an upgrade to the ol tranny. I'm at 30,000 and want to start stacking.

Have you checked the info/videotape that comes with a new truck related to the Allison Trans. There are a number of such things that are normal for the trans. I have a bump like that a few seconds after stopping at a red light in a Toyota Tundra!

I thought that the 100,000 miles covered the engine and drivetrain?
No just the Dmax itself, the Ally and all the rest are 3yrs/36000 miles. This is why I went with the powertrain extended warranty!! I know it sucks but c'est la vie!! :rant: .........SWH...

The "back-up bump" is likely the Limited slip Diff clutch packs. Mine does this and I tracked it down the the rear Diff. Dealer claims it is normal. So far three of my buddies with 2500HD's and limited slip report the same "pop" once in a while while backing up.

Mine does the same thing, but did it worse when it was new. I only get the pop every once in awhile now... I'm at 21,500 miles.

Dan

Thanks for the help. Now I have 2 things that I'll have to ignore every day -- my wife and the "bump".

I would recommend you try what Frank Blum said, mine did the same and I dropped the driveshaft and lubricated it and it was fine. I was also able to pull the drive shaft out of the boot (and replace it without undoing the boot). Mark the drive shaft in relation to the front shaft and rear end, so you get it back in the same place. Was not a big job.

If you change out the diff fluid, there is a limited slip additive that you are supposed to put in too. Some $12 little bottle that you have to get from the dealer.
Might it be related?

Took it to the dealer today - had 150 miles left on my warranty. I shared all of your ideas with the service mgr.and he agreed to drop the drive shaft and lube it. I'll let you know if it fixes the bump.
Thanks for your all of your suggestions.

Intermediate steering shaft?

Does it happen when touching the brake?

Took it to the dealer today - had 150 miles left on my warranty. I shared all of your ideas with the service mgr.and he agreed to drop the drive shaft and lube it. I'll let you know if it fixes the bump.
Thanks for your all of your suggestions.
Tom;
Sounds like I have the same issue. Please let us know.. I have 21 K on 2003 (All trouble free miles)

Thanx

What your hearing is the clutch packs in the locking diff. releasing. If you drive in a straight line in forward then back straight back the thump wont be there because both back wheels will be turning the same speed but as soon as you turn your truck the back wheels turn at a differant speed,like backing into a parking spot, pull forward then back up again you will here the clutck packs release thus hearing the thump sound. Normal.
Right after putting the truck in reverse and backing up about 10 feet or so, I feel a "bump" from under the truck. It doesn't always happen, but it happens every time I start up and back out of my driveway each morning with a cold engine. The first time it happened I thought I ran over something, but now it feels like something's ready to separate itself from the rest of the truck. Anyone got any ideas? Thanks.


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