Bad hubs or transfer case? How to tell.

[adamj]

Having major trouble with 4wd...
When applying load, uphill for example, and only in 4wd (hi or lo) with manual hubs locked of course, there's this buckling feeling like something is slipping and then catching. It feels like it's coming from the front end, possibly the hubs not fully engaged, but could it also be the transfer case?
Anyway how would I go about testing what's wrong with the 4wd before I tear the whole hub/spindle apart? (Never been in there before, so it would be a learning experience either way)
It's slowly getting worse, and seems like after a few wheel rotations it slips and clunks, then works for a few more rotations, and repeats. This is on slick, snowy roads, going straight on (not turning/ujoint related). 4wd still works, front is still engaged, but I'm afraid to drive on it since it feels like I could be doing damage to expensive stuff with each pop.

 

[bucket]

Hmm. I remember driving an AWD Astro van that did similar to your description, it was the t-case at fault. Stretched chain I think it was.

But check the easy stuff first. Like clean/inspect the lockouts. Also check out the front drive shaft, the splines in the slip could be toast.

 

[kickdeez]

Do you know for a fact that your front and rear axles are geared the same? Have you used your 4wd before? I bought my burb with mismatched gears (unknowingly). Never had a need to put it in 4wd until the first snow rolled though. I found out real quick when it started bucking and jerking when I would hit a patch of dry road. Luckily only ended up blowing up a set locking hubs.

 

[Georgeb]

Hubs are pretty simple to service so I would start there. If I recall you had a shop donsome shoddy work once before so there could be an issue with one of the hubs. In the cold the grease may not be fluid enough to allow full engagement. I would use white lithium rather than bearing grease. If that doesn't help I would be looking at the tcase next.
Edit: I would be looking at the driveline next

 

[kickdeez]

Just read through your build thread...impressive work so far!

Ignore my question from before. It looks like you have put plenty of miles on that truck in 4wd, so I am assuming your gears are matched front and rear. That being said, if it were me, I would put the truck on jack stands, all 4 wheels up in the air. Then I would put it in gear in 4wd and see if I could identify and isolate any unusual noises. That would help narrow your area of focus.

The NP205 transfer case is pretty beefy, and more or less bulletproof. I have a hard time believing that your issue is in the case. It seems likely that your issue is with your locking hubs. They are generally the weak link in the front axle. There is also a possibility that something could be binding up in your differential. Possibly a bad carrier or pinion bearing. Maybe a broken ring gear tooth. These are not all that likely though, unless you are wheeling it pretty hard.

 

[77 K20]

I'd agree with Bucket and check the front drive shaft so see if the splines in the slip joint are ok.

That is my project today is to replace my front driveshaft. I can grab it in the middle and move it side to side- as the slip joint is very loose. I'm sure the splines on it would probably strip out if I got on it in 4 wheel drive.

 

[kickdeez]

I'd agree with Bucket and check the front drive shaft so see if the splines in the slip joint are ok.

That is my project today is to replace my front driveshaft. I can grab it in the middle and move it side to side- as the slip joint is very loose. I'm sure the splines on it would probably strip out if I got on it in 4 wheel drive.

Don't want to speak for the OP, but it looks like he had some pretty good work done on both drive shafts this year (judging by the photos on page 3 of his build thread).

 

[77 K20]

Don't want to speak for the OP, but it looks like he had some pretty good work done on both drive shafts this year (judging by the photos on page 3 of his build thread).

Oh wow- right you are. Was just thinking it was a good place to start. Crawl under and wiggle the driveshaft. But with a new one then nevermind.

Very nice Suburban BTW OP... you've done a lot of work to it! (after looking thru that build thread)


So what happens if you do a tight turn in 4WD? Like on a gravel surface. One tire slip and you hop like normal? Or does it make noise?

 

[adamj]

Hmm. I remember driving an AWD Astro van that did similar to your description, it was the t-case at fault. Stretched chain I think it was.

But check the easy stuff first. Like clean/inspect the lockouts. Also check out the front drive shaft, the splines in the slip could be toast.

I hope it's not a stretched chain, I was reading up on that and those symptoms sound a lot like mine, but hopefully it's just the hubs and now I get to install an upgrade!

I will check the driveshaft, but I recently had a new slip yoke welded on, and with an upgraded spline style (16 instead of 32)

 

[adamj]

Hubs are pretty simple to service so I would start there. If I recall you had a shop donsome shoddy work once before so there could be an issue with one of the hubs. In the cold the grease may not be fluid enough to allow full engagement. I would use white lithium rather than bearing grease. If that doesn't help I would be looking at the tcase next.
Edit: I would be looking at the driveline next

Good memory Georgeb! That's true about the shop work, it could be related.
First I've heard of the lithium grease for that, and you could be on to something since it was very cold the last time I was out with it (low teens to single digits). I've only used white lithium for greasing springs and squeaky things, and it comes in a spray bottle. Do they make a thicker type for lubricating things like this? Do you mean to lubricate the selecting dial or the internals of the hubs?

 

[adamj]

Just read through your build thread...impressive work so far!

Ignore my question from before. It looks like you have put plenty of miles on that truck in 4wd, so I am assuming your gears are matched front and rear. That being said, if it were me, I would put the truck on jack stands, all 4 wheels up in the air. Then I would put it in gear in 4wd and see if I could identify and isolate any unusual noises. That would help narrow your area of focus.

The NP205 transfer case is pretty beefy, and more or less bulletproof. I have a hard time believing that your issue is in the case. It seems likely that your issue is with your locking hubs. They are generally the weak link in the front axle. There is also a possibility that something could be binding up in your differential. Possibly a bad carrier or pinion bearing. Maybe a broken ring gear tooth. These are not all that likely though, unless you are wheeling it pretty hard.

I have the NP208 transfer case, so it's not as bulletproof as the 205 that everybody talks about. I believe it's a chain-driven tcase, it takes ATF, and I just replaced that fluid not too long ago, and found that the old fluid looked just fine.

I'm going to try your suggestion, getting all 4 wheels off the ground and running it in 4wd.

 

[kickdeez]

I have the NP208 transfer case, so it's not as bulletproof as the 205 that everybody talks about. I believe it's a chain-driven tcase, it takes ATF, and I just replaced that fluid not too long ago, and found that the old fluid looked just fine.

I'm going to try your suggestion, getting all 4 wheels off the ground and running it in 4wd.

My mistake! I misread it on the first post of your build. Definitely can't rule out a stretched chain then (unfortunately). Also, I re-read your build and noticed that you had some extensive work done to your rear diff due to worn out bearings. Makes me wonder if you have similar wear to your front diff...especially if you had some issues with driveshafts prior to repairing them. Just some things to think about.

 

[adamj]

Tore into the hubs/spindles and I'm not sure why I was afraid of it, not that big of a deal.
I replaced the hubs with Warn Premiums and the 4wd is working like a champ now! So the problem was one of the hubs after all. The transfer case, diff, front driveshaft is all good too. I also drained the front diff and gears look pristine and tight up in there. Took the axle shafts out, splines look good, u-joints good too. I think the problem was the hubs were just not locking properly, no damage to the hub lockouts themselves, probably just poping in and out of lock even though the dials were fully turned to lock position.

 

[adamj]

I did notice the hubs were different kinds though, one had torx screws holding it in, and the other had allen heads. One was a black dial, one had a faded pink dial. Also discovered that brake pads were wearing unevenly, I think it was because shop that screwed me over last time with their shoddy work also did not lube the guide pins or something, so I replaced the brake hardware and lubed the pin a bit.

I'm going to be going back in to the hubs anyway to replace the brake lines since they don't look that great (not terrible, but a safety thing nonetheless). When I go back, I wanted to clarify a bit on what you guys do for lubrication of the spindle and the tapered wheel bearings.

Some questions:
Do you put lube on the spindle?
Should I avoid the threads of the spindle so I can get an accurate torque reading on the lock nut?
What kind of grease? Is it okay to mix? I have valvolene syn power (black stuff) But saw some red stuff on the spindle, and also some white stuff in the hub in the space between the inner and outer wheel bearings.
Spindle bearings? Is that something I should re-pack? I didn't want to mess with it.
How to lube the hubs? Do I grease the splines of the locking hubs and splines of rotor/hub assembly? How to grease the turn dial, with what lubricant?
What's necessary to lube with the brakes? Guide pins? Anti seize on back of pads?

If anyone can answer just one of those q's would help me out a bunch!

Thanks!

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[yevgenievich]

It would have been best to check for play in the bearing before tearing it all apart. It looks fresh with new greas, so probably bearings are good and just need to be repacked before going in. Grease looks like mystik red or equivalent. Any high temp grease would work, some are better than others. You might wany to check the inner seal and maybe replace the axle seals at the center diff. Also check/replace the ball joints. I am about to take all apart again as shortly after replacing wheel bearings, ball joints starting to fail.