Hello all, I come to you today with yet another problem with my 07 H3. Ive done searches on this and haven't found anything related to my problem.

SO. I'll be driving along and traffic in front of me slows a bit, so I let off the accel for a bit and coast.. then when I give it some gas there is this huge clunk that jolts the truck. The weird thing is that at higher speeds the clunk is less noticeable, but say I'm going like 20 in a parking lot and then coast to 15 and give it gas the clunk is HUGE. This will also happen when I'm at a set of lights.. when it turns green, I press the gas.. Clunk.. then it goes.. the clunking lasts for less than a second.. and then she drives fine.. This happens every day.

When I got new tires put on my Truck I requested that they check out my engine and transmission mounts.. they told me the mounts were all solid.

What do you guys think the problem is..?

 

U-Joint ?

 

Thats what i thought at first too.. but the shop said they were fine and i had 2 different people look at them.

 

Mine does the same since I bought it as well, i just figured "it's a 4x4 SUV on a pickup truck frame/drivetrain, not a luxury sports car" doesn't seem like anything's wrong with the tranny I"m planning on flushing the transmission and differentials in a few days anyway as part of the 90k maintenance, maybe that will help, I'll keep you posted...

 

All three of my h3s have done that. It wasnt until I looked closer to my 2006 I own now that I realized it was the three front differential mount bushings being worn out. Replacing the diff mount on the crossmember made the biggest difference!

 

I have had that diagnosed at a dealer and they said propeller shaft needs replacing. The tech was gone when i got tehre so I didn't get a chance to talk with him directly but my guess is u-joints are worn and it was easier to just replace the whole thing rather thazn mess with the u-joints. The service manual seems to indicate the same.

 

This sounds like its going to be a costly fix...

From what I gathered.. I'm going to need a new propeller shaft, u joints, and differential mount bushings... darn.

might not need the front mounts because the sound appears to be coming from the back of the truck.

 

I had issues with my 2008 Hummer and it turned out to be the front drive shaft was not disengaging completely causing a thumping noise under my Hummer. I could actually feel it though the floorboard.
It was under warranty and the dealership said that it's not uncommon on the Hummers.
I've owned 4 Hummers now and that was my 1st experience with it.

 

When I get back to work on monday I will take a look at what the dealer had written down for the prop shaft, I don't recall it being too bad if you do it yourself.
The crossmemember bushing isn't something somethign you can buy seperately, you have to get a new crossmember unless you use the fix that some others have used. I'm sure you can find the threads with a search

 

If you could that would be awesome