Question about drive train slop

[Doubeleive]

So as some of you may be aware at 160k I decided to have the dealer replace the u joints.
Well they fubar'd that to hell and upon picking the vehicle up immediately upon getting on the freeway I had some pretty bad vibration they were closed and so I limped it home about 10 miles at 55 to keep the vibration to a minimum, I had it towed back to the dealer and they replaced one u joint that was jacked up. Still had some vibration so I had the drive shaft re balanced and that helped a bit. At this point I now had some good amount of slop enough that it feels like the rear end is dipping when I accelerate and I can feel it when I brake as well, no clunk noise but I can feel it. So I drove it like that for 2500 miles and this hasn't changed. I ordered a new drive shaft because I figured maybe the slip yoke was f-ucked and maybe a shaft ear. Got the new drive shaft in and vibration is all gone but I still have the slop now and had none before this at all. So my question is could this vibration have messed up the transfer case and or pinion/carrier in the few short miles it was driven. And is there a way I can tell if it is the transfer case or rear end? Like is there a minimum amount of play that would tell me if one has more than it should or not?
I'm assuming I will have to drop the drive shaft and see which end moves more?

 

[OR VietVet]

I don't have an answer for the "amount of play that is allowable" question. But, consider this, the amount of revolutions the old driveshaft turned in the "few short miles" it was driven. That runout can do some damage, depending on the amount, to other components, also depending on their age.

 

[Doubeleive]

I also elliminated other possibilites by inspecting pretty much everything, shocks, springs, control arms, sway bars, end links, panhard bar, etc
it has air ride and the bladders hold air and I recalibrated it anyway just to rule it out.
fluids are good (fresh) in both the transfer case and rear diff so kind of hesitant to drain and check for any metal
it is awd so it technically has no "park" function it holds the front and rear by binding them together, if you lift either end it spins so whatever i check will have to be while on the ground or I can grab a extra set of ramps and put it on 4 ramps to give me room underneath

 

[j91z28d1]

can you explain what you mean by drive line slop?

I honestly don't think you hurt anything in those few miles.. I mean you're not going to hurt a ring and pinion, worst case in rear would be if you drove it long enough, it might make the crush sleeve a little loose and have some bearing slop, but you would have a leaking seal and could feel that by hand. again I don't think you drove it long enough. from my bad drive shaft days you'd need to go like 10k miles before the rear would show some slop, and I don't think you'd ever feel 0.050 slop while driving. the front, you could definitely wear the bushing in the tail housing the yoke rides in. but you'd feel slop by hand and it doesn't take much for the seal to start leaking. again long before you felt it driving it, you see signs under it.

like do you think shaft is spinning some before the truck moves?

the leaf spring obs has a weird thing where when you took off the axle would wrap up like normal but the yoke wouldn't slide in and out while under tension. under braking too, the whole thing got bound up. let your foot off the brake it it would pop back. it was very annoying. there was a special grease for the splines. but it was temp, the long term fix was a nickel plated yoke gm sold. I got one for mine, used the special grease and I never had the odd thumping and binding again. but I'm not sure these trucks being coil spring if that's even a thing..

I am very glad to hear the Dorman shaft is smooth. that's a relief.

 

[swathdiver]

Propeller shaft runout up front is .046 inches and out back is .055 inches.

Transmission or transfer case output flange play is supposed to be .008 inches.

Differential pinion shaft play is not supposed to exceed .002 inches.

 

[Doubeleive]

can you explain what you mean by drive line slop?

I honestly don't think you hurt anything in those few miles.. I mean you're not going to hurt a ring and pinion, worst case in rear would be if you drove it long enough, it might make the crush sleeve a little loose and have some bearing slop, but you would have a leaking seal and could feel that by hand. again I don't think you drove it long enough. from my bad drive shaft days you'd need to go like 10k miles before the rear would show some slop, and I don't think you'd ever feel 0.050 slop while driving. the front, you could definitely wear the bushing in the tail housing the yoke rides in. but you'd feel slop by hand and it doesn't take much for the seal to start leaking. again long before you felt it driving it, you see signs under it.

like do you think shaft is spinning some before the truck moves?

the leaf spring obs has a weird thing where when you took off the axle would wrap up like normal but the yoke wouldn't slide in and out while under tension. under braking too, the whole thing got bound up. let your foot off the brake it it would pop back. it was very annoying. there was a special grease for the splines. but it was temp, the long term fix was a nickel plated yoke gm sold. I got one for mine, used the special grease and I never had the odd thumping and binding again. but I'm not sure these trucks being coil spring if that's even a thing..

I am very glad to hear the Dorman shaft is smooth. that's a relief.

the dorman slip yoke appears to be nickel or nickel plated, I used some mobile 1 high temp red grease and put some in there not a lot, maybe a couple tablespoons. wasn't really sure how much it should have and when I removed the old one there was no grease in there and the dealer "said" they lubed it before I left for my trip. I presume it gets absorbed into the transfer case fluid? at least that's what I have read. If it just needs more grease then great
what I am feeling is when I accelerate and my version of accelerate is pretty much pedal down I am no slacker, I then feel what seems like the @ss end drops but there is moment where there is nothing but @ss drop and then it goes. seems like the drive shaft is moving then the vehicle moves after the @ss drops so SLOP. previous to this whole fiasco it didn't do that when I said go it went without hesitation. now the @ss drops then it goes.
and if I hit the brakes that movement is in reverse, then gas it again and it does it again. If I am already moving slower faster without hitting the brakes it doesn't do it.

 

[Doubeleive]

Propeller shaft runout up front is .046 inches and out back is .055 inches.

Transmission or transfer case output flange play is supposed to be .008 inches.

Differential pinion shaft play is not supposed to exceed .002 inches.

thanks James I am going to try and hand test it somehow or get it up on a lift and see I can hand test it.
those specs seem pretty tight I assume that is side to side, nothing is leaking
I don't think runout is my issue

 

[swathdiver]

the dorman slip yoke appears to be nickel or nickel plated, I used some mobile 1 high temp red grease and put some in there not a lot, maybe a couple tablespoons. wasn't really sure how much it should have and when I removed the old one there was no grease in there and the dealer "said" they lubed it before I left for my trip. I presume it gets absorbed into the transfer case fluid? at least that's what I have read.

Motor mount still good?

The factory slip yokes are also nickel plated.

We are not to use grease on the rear splines of the yoke. This can clog up the pump in the transfer case. Just use Dexron VI. You can grease the front axle's slip yoke as that shaft is external.

Years ago I misread this and spouted off all over the internet to use grease, even bought a can for myself. Then when I finally got around to doing it myself, I learned that I had read it wrong and set about with Gary making all my posts correct or posting corrections in the thread.

 

[Doubeleive]

Motor mount still good?

The factory slip yokes are also nickel plated.

We are not to use grease on the rear splines of the yoke. This can clog up the pump in the transfer case. Just use Dexron VI. You can grease the front axle's slip yoke as that shaft is external.

Years ago I misread this and spouted off all over the internet to use grease, even bought a can for myself. Then when I finally got around to doing it myself, I learned that I had read it wrong and set about with Gary making all my posts correct or posting corrections in the thread.

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

 

[j91z28d1]

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.