Question about drive train slop

[Geotrash]

You seem to be describing a very specific feeling that does not correlate with loose mounts but it's probably worth checking the front diff mounts anyway. The way you're describing it it's almost like the rear axle is torquing causing the squat feeling before it goes. But I know you said you checked all of the mount points and bushings back there.

Might be worth setting up a GoPro under there to see what's happening when you take off from a stop.

 

[Doubeleive]

You seem to be describing a very specific feeling that does not correlate with loose mounts but it's probably worth checking the front diff mounts anyway. The way you're describing it it's almost like the rear axle is torquing causing the squat feeling before it goes. But I know you said you checked all of the mount points and bushings back there.

Might be worth setting up a GoPro under there to see what's happening when you take off from a stop.

ya I am going to pop the hood and check the motor mounts but if I broke a h3 mount not quite sure how once it started vibrating I babied it, then had it towed back to the dealer, then they test drove it I doubt very far, then fixed the u-joint and then I rode with the mechanic for a test drive of maybe a couple miles and shortly after that I noticed it.
After installing the new drive shaft I really expected that to go away but it didn't. I think it less pronounced than it was with the old shaft, before it would almost make me feel sick in my stomach now it's slightly less of a drop feeling. really feel it in the very rear end based on seat of the pants.
I have a couple go pro's around here just have to zip tie it to something don't really have much for mounts

 

[Geotrash]

I also should mention that there is a huge difference in driveline slop between my 2007 with 235K and my 2012 with 137K. The 2007 has way more slop in the uptake when transitioning from coasting to accelerating. So much so, there is a clunk. The 2012 has almost no slop. I've replaced motor and front diff mounts on the '07 but it's still there. I've noticed that I have a lot of rotational play in the transfer case output shaft which I attribute to play in the chain:

 

[Doubeleive]

hmm seems like there was a specific grease/lube in a tsb for the 96. if I remember right you could buy it at the dealer. but yeah, from the sound of it, it's a suspension squat type of thing, not drive shaft bearing type of thing.

I honestly got nothing, unless your old shaft yoke was not sliding in and out smoothly and limiting the axle squat? like say a torque arm would do in that style suspension? I don't know, just tossing out ideas at this point. I'd have to get under my truck and see what even limits axle wrap under acc and decel.

you guys are better at finding tsb's than me, but I believe it was called
Genuine GM Fluid 19257121 High Temperature slip yoke grease. here's to hopping gm wasn't selling grease that clogged up pumps over a clunk. haha

but again. I don't think it's your problem, unless it wasn't slipping before and now is.

previous to all of this like 2-3-4 years ago I was getting some clunk it was the front diff mounts, those were replaced then both motor mounts were replaced with the h3 mounts and even punching it off the line to the floor other than some normal split second drive by wire hestitation there was no slop and the drive shaft has been out and in a few times because I had the transmission re-built for 500hp because the torque converter was goofing up and I could feel that as well which is totally different and the front end clunk was different also.
this is something new I haven't felt before

 

[Doubeleive]

my best explanation is it feels like everytime you go to walk someone is tugging on you back belt loop right as you go to step for second and then releasing instantly everytime you stop giving you slack, although the slack is not as much as the tug

 

[swathdiver]

I wonder why the service manager told them to grease the slip yoke then? this was right after I had it rebalanced.
I am pretty sure the hummer motor mounts are fine and I am not getting any clunk noise or sound.
just can feel it in the rear end

Well, he either used the term generically and they used Dex6 or messed up and used grease. I was looking for the TSB and was reminded about driveshaft phasing. Did they install the new shaft on the same splines and in same position on the yoke? The only way you'll know is if they made witness marks unless you can slip around back and talk to the techs that did the work.

 

[swathdiver]

OK, just found it for mine, Bulletin Number 09-04-21-003D. Then I found this one for my 2013: 99-04-20-002H

There's also one for the pickups, about fuel sloshing around in the tank causing a bump like feel. Never felt that in mine.

Maybe it's time to drop the rear diff cover for a looksee?

 

[Doubeleive]

Well, he either used the term generically and they used Dex6 or messed up and used grease. I was looking for the TSB and was reminded about driveshaft phasing. Did they install the new shaft on the same splines and in same position on the yoke? The only way you'll know is if they made witness marks unless you can slip around back and talk to the techs that did the work.

I installed it, I just slid it on there and bolted it up.
I want to get under it again and look some more and see if I feel anything, been busy and it's hot as satan out
should have a little time tomorrow

 

[donjetman]

I also should mention that there is a huge difference in driveline slop between my 2007 with 235K and my 2012 with 137K. The 2007 has way more slop in the uptake when transitioning from coasting to accelerating. So much so, there is a clunk. The 2012 has almost no slop. I've replaced motor and front diff mounts on the '07 but it's still there. I've noticed that I have a lot of rotational play in the transfer case output shaft which I attribute to play in the chain:

My 07 awd has always had a lot of slop, most of which is in the transfer case.

 

[j91z28d1]

My 07 awd has always had a lot of slop, most of which is in the transfer case.

can you feel it while driving or just by hand when you're under it.