Play in rear diff?
 

I get a little bit of a 'clunk' from the rear diff sometimes. Usually happens when I am coasting below 30mph and then get back on the accelerator. My first thought was a u-joint. We had it up on a lift at a tire store yesterday and checked it out. The u-joints are good but you can turn the driveshaft and there is play in the rear end. The guy at the store said this was something GM had issues with.

My questions are: Is this something H3 owners have seen often? How much play is okay? The repair, if I need a repair, should be covered under my drive train warranty. But I don't want to go in there and have them tell me it is 'within specs' and charge me $120 for the diagnosis. I just know that little issues if not addressed can lead to more stuff breaking and then it is big issues.

ours does this as well, I assumed it was normal but would be nice to know for sure.

Check the bushing on the front diff crossmember. When these fail, they feel like its a rear u-joint or in the rear end. Kinda common problem, if you are within warranty Gm will replace it. (i've had 2 fail, a few others are on 3 or 4). If not search for the diy repair threads or you can pick up a spare for a few hundred.

Driveline slop is normal.

You can feel it in any vehicle, but more so with a 4x4 because the T Case adds into the equation with the Trans and U Joints.

I've had the same thing on every 4x4 GM vehicle since 1995. It is nothing to be concerned about (YES it is anoying sometimes).

For piece of mind, you may want to inspect the bushing on the front Diff crossmember. A worn bushing produces a totally distinctive clunk and does not feel like it is coming from the rear, and you can feel it in the drivers floor board.

Hope this helps!:D

gotta add this
 

on a RARE ocassion in 2 h3 i have driven i felt this.
the 07 up to 56000,and a fresh 10 under 4000.

it seems to be related to the way the engine rpm changes,drops, and not so much the way i run the gas feed as the way the eng is running in a warmup cycle

there must be a "sweet spot" in the cycle where the rpm changes that does not relate to "my foot"! because i swear i cant "make it happen".

but on RARE ocassions it does.

most cars in the past and 2 h3, i must say its not an issue.
when it was an issue,,a real thing,it drove me nuts and i had to do something.

so bottom line,if u feel it regularly,,my opinion,,its an issue!

I posted on this site awhile back about excessive play in the rear end. Mine used to hum on the freeway when I was on the gas, and silent when coasting. The slack I exhibited was a combo of both the front diff bushing (which I still have yet to find time to replace) and the rear end pinion bearing. I went down to have an eaton elocker installed and upon removing the diff carrier, the tech noticed that the pinion bearing was on its way out. You could grab the pinion (with the driveshaft removed) and wiggle it. His thoughts were the play in the bearing allowed uneccessary wear on both the ring and pinion (hence the noise). He mentioned GM has been putting the "new" bearing in and they don't hold up. We installed an older timken bearing with thicker roller bearings, new ring/pinion and whala...no noise and tighter driveline. I still have slop due to front bushing and being a full-time 4wheel drive, but there was a noticable decrease and my "clunk" on and off the gas is gone. I would chalk it up to slack in all areas if you have no noticeable noise. Mine had 80,000 when it was replaced. Hope this helps.

I have a similar issue with my 2008 but I'm only at 32,000 miles! Although it's not all the time usually at a stop light or taking a corner and them getting back on the gas I get what feels like a pause then catch. I haven't tried to move the drive shaft by hand to check for play. Anyone know how much play there should be if any?? Or since I'm under warranty maybe I should just take it in..