Slack in my drivetrain?

[03envoy]

I'm having some weird issues with my drivetrain that I think is linked to a dry slip yoke but I don't know if that's the only issue. If I hit the gas doing any speed I get a solid and harsh thump and i can describe it as like the drivetrain taking a minute to catch the "slack" and then it catches and goes. But it's delayed and has a solid jolt. What could be causing this?

 

[The_Roadie]

The slip yoke has so many splines that I can imagine it making a noise when you stop and the rear end height changes (that is the reason there is a slip yoke), but I cannot imagine having so much slop that it has a rotational backlash issue.

Much more likely to be a bad u-joint, discussed in many other threads, one just recently. Less likely to be bad gears in the rear diff. What's your fluid change and level check history on that?

 

[03envoy]

The slip yoke has so many splines that I can imagine it making a noise when you stop and the rear end height changes (that is the reason there is a slip yoke), but I cannot imagine having so much slop that it has a rotational backlash issue.

Much more likely to be a bad u-joint, discussed in many other threads, one just recently. Less likely to be bad gears in the rear diff. What's your fluid change and level check history on that?

Replaced fluid at 120k when I got it. One u joint was just recently replaced. The one at the transmission could be bad.

 

[Sparky]

When mine was doing this it was something in the rear end. That's why I rock an 8.6 now

I didn't think to pop the cover and look at it. I should have just to see what was going on in there.

 

[03envoy]

Only thing is when I lift the truck up and twist the driveshaft, all the "slack" so to speak is in the slip yoke/ u joint area. The rear seems normal and tight. The g80 seems to function normal.

 

[03envoy]

What else could be causing this besides a bad u joint? The u joint seems of to me, it could be bad though. Is there anything else I can check before I replace the u joint? Thanks,
Trent

 

[The_Roadie]

If you're on a lift or jack stands, the u-joint is the easiest to inspect. The interior of the differential, where the bearings and gears are, is much ickier to get at by removing the rear cover.

 

[C-ya]

I'm going to piggyback on this thread as it seems my drive line has some slack and noise in it. I notice it when backing into the driveway after work, or when maneuvering around (3-point turn, etc.) and you are shifting back and forth between D and R.

I backed the rear wheels up onto a set of ramps and had my dad go from D to R and back, letting it settle into the gear before changing. The slip joint/tailshaft area seemed to make a "clunk" sound and there was a slight twist of the driveshaft that happened when the clunk happened. Obviously there was no complete rotation as the brakes were applied and the vehicle was not moving, and I understand that the tranny is shifting rotation of the inner workings. The u-joints appear to be solid with no movement. Is that changing of rotation all I'm hearing? I'm not getting the clunk while driving, and I even tested it by down shifting (no noise/clunk), and by accelerating after coasting.

I changed the rear gear oil and the innards looked fine. My G80 functions normally.

 

[Wooluf1952]

IMO, it depends on the sound. If it is a dull thud sound, I believe that's not unusual. If there is a metal on metal clank sound, there is something worn.

 

[C-ya]

Yeah, mine is kind of a dull thud, not metal on metal. I'm not freaking out about it yet. Just noticing things that sound a little "odd" and evaluating.

 

[Sparky]

Sounds normal. You'll always have a little bit of slack in the driveline either direction when shifting one way to the other.

My old rear diff would thunk/clank when letting off and getting on the gas before I replaced it. That's usually a bad sign

 

[03envoy]

IMO, it depends on the sound. If it is a dull thud sound, I believe that's not unusual. If there is a metal on metal clank sound, there is something worn.

The gears have a distinct sound. A clunk is what I had which was a bad u joint at the diff. Now I have a clunk that seems to be coming from the rear diff, but I haven't checked anything out yet. When I pull the rear diff cover what am I looking for other than metal chunks?

- - - Updated - - -

Sounds normal. You'll always have a little bit of slack in the driveline either direction when shifting one way to the other.

My old rear diff would thunk/clank when letting off and getting on the gas before I replaced it. That's usually a bad sign

That's exactly what mines doing. What causes it to do that?

 

[03envoy]

I just went under there and seem to have slack on both the differential and transmission/transfer case.

Here is a video of the rear diff. And driveshaft. Notice the "slack" that seems to be there.

[video=youtube_share;W_RdIK-ZjVM]http://youtu.be/W_RdIK-ZjVM[/video]

 

[03envoy]

Here is the link to the thread on ORTB. We think it may be linked to worn gears inside the transfer case.

offroadTB.com - View topic - 2nd Bad U-joint... I think.

 

[C-ya]

03, mine is nothing like what you show. Good luck in your quest for a fix.

 

[03envoy]

After a little messing around the closest noise I could get to what I'm hearing from the rear axle is this: I think this is the noise.... What could be causing this noise?

[video=youtube_share;8IYDScZThuI]http://youtu.be/8IYDScZThuI[/video]

 

[RayVoy]

All I can add, is that there is noise in the linkage between the transmission and the rear wheels.

There is some rotational slack in the diff gears, a little (very little slack in the axle splines, there is a little (again very little) in the yoke; but, the area with the most slack is the two u-joints.

Don't take this the wrong way, but you could have pulled the driveshift and looked at the condition of the joints over the same time it took to make the vid.

I'm not trying to give you a hard time, just pointing out how easy it is to pull the driveshift.

Four bolts at the rear u-joint and the shaft is out.

When you get it out, I'm sure you will find most of the wear will be in the front u-joint.

Just a note, mark the top of the shaft (as it sits) and the top of the pinion yoke so the repaired driveshaft goes back in as it cane out to maintain any balance issues.

 

[03envoy]

All I can add, is that there is noise in the linkage between the transmission and the rear wheels.

There is some rotational slack in the diff gears, a little (very little slack in the axle splines, there is a little (again very little) in the yoke; but, the area with the most slack is the two u-joints.

Don't take this the wrong way, but you could have pulled the driveshift and looked at the condition of the joints over the same time it took to make the vid.

I'm not trying to give you a hard time, just pointing out how easy it is to pull the driveshift.

Four bolts at the rear u-joint and the shaft is out.

When you get it out, I'm sure you will find most of the wear will be in the front u-joint.

Just a note, mark the top of the shaft (as it sits) and the top of the pinion yoke so the repaired driveshaft goes back in as it cane out to maintain any balance issues.

I'm going to pull it soon. Can I pull the yoke from the rear diff and grease that also? I can just mark that and slide it out grease it and put it in the same way?

 

[RayVoy]

Can I pull the yoke from the rear diff and grease that also?

No, it is not a sliding yoke.

 

[03envoy]

Still haven't figured this problem out. It has to be linked to the rear diff, or transfer case. Other than pulling the diff cover what are my options?

 

[IllogicTC]

Pulling the differential cover isn't bad, it just seems scary because that's what service shops want us to think

Seriously, just be sure to have a new gasket on hand appropriate to your RPO code (GU6,GT4,GT5) and enough synthetic 75W-90 to fill her back up, and you're ready to crack it open. Unless you have the G80 RPO code. And then, the problem may be linked to the locker system, I don't know.

 

[03envoy]

Pulling the differential cover isn't bad, it just seems scary because that's what service shops want us to think

Seriously, just be sure to have a new gasket on hand appropriate to your RPO code (GU6,GT4,GT5) and enough synthetic 75W-90 to fill her back up, and you're ready to crack it open. Unless you have the G80 RPO code. And then, the problem may be linked to the locker system, I don't know.

Yes. Not worried about pulling the cover but the G80 has nothing to do with this when I'm driving normally in the summer. I'm honestly just waiting for one the rear diff to blow which I hope it doesn't. Or the transfer case to take a shit.

 

[IllogicTC]

Why wait when you could just open it up and take a look? Could potentially save hundreds by checking before it's too late.

 

[03envoy]

Why wait when you could just open it up and take a look? Could potentially save hundreds by checking before it's too late.

Because it's freezing outside. And I can't do anything if something is wrong with my rear diff other than swap it.

 

[IllogicTC]

True, I know that feeling. Currently whizzing snow down over here which put a damper on my day, so I guess it's MineCraft and GMTNation day again

And I suppose a full check isn't exactly free since you have to put in new fluid and whatnot. But have you at least checked the fluid level? It may be able to tell you something without having to crack it all the way open. Could use May03LT's trick of dabbing a white ziptie just inside to get a feel for the level and have an oil sample to examine.

It'd be nice to at least be prepared, if you blow the rear diff at highway speeds it could get messy but you may have been around the block on crap going on vehicles a few times, I don't know Best of luck to you man, hopefully if it holds together well enough til it warms up a solution can be found before something breaks!

 

[dfc739]

I have an almost identical sound in my driveline. I checked it out when I changed my differential fluid at 200k. There was almost zero slop between the pinion and ring or any other components. Before you bother pulling the diff cover, take loose the u-joint at the pinion and try rotating the driveshaft back and forth. I'm 99% sure my noise is coming from the transfer case but you could be different.

 

[Davidp]

I have an almost identical sound in my driveline. I checked it out when I changed my differential fluid at 200k. There was almost zero slop between the pinion and ring or any other components. Before you bother pulling the diff cover, take loose the u-joint at the pinion and try rotating the driveshaft back and forth. I'm 99% sure my noise is coming from the transfer case but you could be different.

I bought my 06 Envoy new at around 18000 miles mine started doing this. I took it to dealer they checked it took the whole drive line apart. No Fix they took transfer case apart no problem found. They flushed transmission. They checked the backlash. The thing still does to GM has a service note about this they say its normal operation. I said bull HJB GHTY&^&^TT&8783423 and a lot of other things. But after talking to GM about a dozen times and taking it to3 different dealerships. They asked what would make me happy I walked out with a 100,000 mile drivetrain warranty.

 

[IllogicTC]

They asked what would make me happy I walked out with a 100,000 mile drivetrain warranty.

Not bad compared to the ridiculously short standard warranty!

 

[03envoy]

I have an almost identical sound in my driveline. I checked it out when I changed my differential fluid at 200k. There was almost zero slop between the pinion and ring or any other components. Before you bother pulling the diff cover, take loose the u-joint at the pinion and try rotating the driveshaft back and forth. I'm 99% sure my noise is coming from the transfer case but you could be different.

It's linked to one, the transfer case gears, two the differential back lashing, or three transmission. I've been under there, all fluids are up to date.

 

[Texan]

It's linked to one, the transfer case gears, two the differential back lashing, or three transmission. I've been under there, all fluids are up to date.

A number of years ago, I had a RWD Chevy that cratered the rear u joint. I replaced it, and a few months later
I began to hear a strange noise under the car. It got progressive worse, and I finally got back under and removed
the drive shaft. I discovered that the front u joint was stiff as a board. It was totally dry of grease, but did not
have any play in it. New front joint solved the problem. There is a bushing in the transmission tail shaft that
the sliding yoke rides in that could be worn.

 

[03envoy]

A number of years ago, I had a RWD Chevy that cratered the rear u joint. I replaced it, and a few months later
I began to hear a strange noise under the car. It got progressive worse, and I finally got back under and removed
the drive shaft. I discovered that the front u joint was stiff as a board. It was totally dry of grease, but did not
have any play in it. New front joint solved the problem. There is a bushing in the transmission tail shaft that
the sliding yoke rides in that could be worn.

Defiantly going to pull the driveshaft.
Thanks for the input.