How to quit down 4wd

"Erik" wrote> 4WD Howls in AWD and 4Hi under load.

$500 dollars for the rebuild? The guy can't have put much more then the side and pinions bearings in. Is this a pro doing this work? How do you (and he) know that the gear set isn't toast? The problem with gear sets is that if you run any gear set for any extended length of time with worn bearings, you inevitably wear the gear set in such a way that it will never be quiet again...no matter what you do. Most of these front diffs that I'm rebuilding are getting new gear sets, as the amount of "play" that the gear set has been running at does damage to the gear set, and even if you set it back up perfectly, it will still be noisy.

Proper pinion and side bearing preload is fairly critical on these front diffs. Hopefully he is using a deflection inch/lb torque wrench in order to get the correct pinion bearing preload and then the correct pinion/side bearing combined preload.

Ian

I have a `97 Z71 w/73,000 on it. I bought it in `99 w/24,000. It has always howled in 4 wheel. Took it to my buddy at the shop.He changed fluid and checked everything. Nothing wrong. It`s just the way it is. I beat the hell out of mine,so there can`t be anything wrong.

Good points.

I think that proper gear adjustment and alignment is very critical as well.

Actually, it was $450, $200 parts, $150 Labor + Tax.

It is a local transmission shop. He was one of 2 guys in town that would do it other than the dealer.

I have no clue when it comes to rebuilding diffs. Thats why I took it to the shop. When he quoted the rebuild he did say that I would be getting into a lot more money if the gear set needed replaced. After he got it apart, I asked him if the gear was ok and he said it was.

quiet again...no matter what you do. If this is the case, is the noise just a nuisance or will it cause premature failure?

Are you finding that races of the side bearing are pitted like the guy told me?

Hopefully, they decide to take it apart again and make it right. They did give me a 30 day warranty. I guess if tries to say that this is normal for these trucks then I'm probably screwed.

Thanks a lot for your replies

"Erik" wrote

No doubt, there are very few mechanics anymore that know how to, or want to tackle a differential overhaul. I'm very fortunate that when I was an apprentice, I got handed tons of diff work (it's considered the s*it work) and as a result got a good handle on how to overhaul a diff properly.

Ok.....he may be right, he may be wrong. That's the other thing about a gear set, it's really almost impossible to look at the gear set and tell if it will be noisy or not when you set it back up. If there has been any kind of play in the bearings, I usually estimate the gear set as part of the repair, and if the customer doesn't want to go for that, it either doesn't get done by me, or I will put bearings in only with major disclaimers about how the gear set could still be noisy.

For the most, it will simply be a nuisance. The important thing is that the bearings are in good shape and properly adjusted. But most customers we deal with expect the diff to be perfect when they are handed the vehicle. And of course, much of the diff work we do is warranty, in those cases, we put in whatever parts we deem necessary to make sure that gear set does not "come back".

Yes, it's always the side bearings that go. At least, everyone that I've seen apart in our shop has been the side bearings.

Hopefully you can get it resolved. I don't know what the tech said to you about the diff, so I don't want to slam him as I only have your side of the story. You might ask him if he checked the pattern of the gear set when he had it all back together? He'll probably say yes, but you never know.

Ian

I am not slamming him either. The shop seems to be treating me fair. I knew I was taking a bit of chance without taking it to the dealer. However, I'm get the impression that the dealer is big bucks. I also looked into getting a used one but after seeing you state that you have seen numerous bad diffs, I was worried about getting another bad one.

Well, I took the truck to the shop today. They put it up the rack and no noise in the front end in 4wd. When he did this before the rebuild, it was making quite a bit of noise. Hopefully, that is progress. I told him it only makes the noise under load. So, we took it for a drive and sure enough it howls in 4wd when you give it gas. He said something about a crush bearing and that he wanted to put a torque wrench on the pinion. I would guess that means he is going to check the pre-load. I left it with him, but he didn't get a chance to look at it. He said that he will first thing tomorrow.

"Erik" wrote

Right...well there is no doubt that the dealer would be more expensive. Most likely they would have recommended a gear set.

Let us know what they find out.

Ian

Well, He said basically the same thing you did. Maybe he's reading this thread :). He sad that the pattern of the gear set may have change because of the bearings be shot. He said sometimes after you drive it for a while that it may quite down. So, he told me to drive it for a couple of weeks and if doesn't quite down then bring it back. He also said that he tightened up the pinion nut a bit and that quited it down some. I didn't notice any difference.

It would seem to me that the bearing being shot wore the gear set and that the howl I was hearing ( or at least some of it ) was due to the gear set from the start. I am skeptical that driving it for a couple of weeks will make a difference.

I imagine in 2 weeks I am going to be making a decision on the gear set. Thats going to be a tough one. Especially, if I have to pull the diff again and pay for the labor to have taken apart again.

This morning I crawled under my truck to change the output seal on of TC. I have been putting it off until I'm certain the diff is OK. The leak is very small.

Well, while I was under there I checked the front diff. The pinion seal is leaking. I am definitely going to be taking the truck back to the shop that did the rebuild now so I may as well let them change the tc seal since they are going to be pulling the drive shaft anyways.

Also, I am not sure if my diff has quited down any or if I have got used to the howl. It doens't seem to make as much noise as when I first picked it up. Though, it still howls when under load.

Is it more likely the pinion seal is leaking due to improper preload or because of the gear set pattern? If its the preload, is it likely I trashed the side bearings again?

"Erik" wrote

If the seal is leaking, you have a number of reasons why it's leaking. It was improperly installed, perhaps damaging the outside circumference of the seal, the surface that the seal goes into could have been nicked by a careless tech removing the original seal, the preload on the bearings may not be sufficient, allowing the pinion shaft to flex under load, or the surface of the yoke that the seal rides on might be pitted or grooved.

Improper preload of the pinion bearings won't have any direct effect on the side bearings.

Ian