04 front diff already gone?

[Detroit Dan]

Started getting a lot of howling noise from the front of the wifes 04 Avalanche 1500. Sounds identical to the front diff on my 02 Denali when it failed. Checked and there was hardly anything in the diff, filled it up with full syn 75/140, didn't quiet it down. BTW, there was no indication of any leakage anywhere. Denali I was told went at 87k because the Denalis and Escalades are AWD, but this is selectable 4wd. Course, it all turns all the time anyway. The Denali cost a fortune to have a rebuilt diff put in, I'm not going that route again. I'll either rebuild it if I can or use one out of a parts truck.

Any idea where I can find info on what years are interchangeable? I'm pretty sure it's a 3:73, of course I will confirm that before touching it. Just need to know if a 2000 or a 2002 or what have you will fit in the 04.

Going to double check the wheelbearings again, but I don't think it's that. Usually a wheelbearing changes sound when you're turning the wheel.

79k and the front diff had no oil in it, the PS pump was almost empty, and I have a tranny line seeping now too. I usually check things every oil change, might have skipped it last time because of the cold, but can't understand how the truck is all of a sudden just falling apart. Just put new shocks in and was about to spring for 4 tires, but going to have to figure out the front diff thing first. Speaking of tires, I wonder if a bad tire could be responsible for the noise? They are pretty worn. But, the diff was so low, that's gotta be the problem.

 

[stacks04]

yup, dont doubt it. they are junk. had a batch of bad bearings in them. get bearings and a puller. pretty easy to do.

 

[Detroit Dan]

yeah, I definitely want to try to do it myself. I heard from a service tech who works for a Chevy dealer, says they always go at around 80k, and it's always the same thing as what I experienced. They get noisy, the bearings are wiped and theres no oil in them, with no signs of leakage. Have to wonder if GM knows exactly how much oil they need to put in to make it last longer than the warranty. Shame on me for not checking the oil level in the diff. I check and/or change everything in my DD/plowtruck every season, but wasn't particularly worried about the front end of a street truck.

What a shame, they can't or won't build something right. My 82 has a D60 in the front, that will probably last another forty years whether it's got oil in it or not. My 97 3500 has taken unbelievable abuse for years and is showing no signs of giving up at 173k. This 04 sees 4wd use only on snow days and it's failing before 80k. Nice.

 

[Detroit Dan]

Well, ordered all the bearings from Advance, pulled it out and tore it down. Learned that Advance gave me two sets of all the races and roller bearings, but none of the needle bearings. Spent half of Saturday chasing parts all over the state. Worst part was the bearing pressed onto the pinion, that was a real PITA. Finished it up Sunday and got it back together. Filed it with 75/140 full syn and took it for a ride. Noise is still there, and now there's something wrong with the 4wd. Ugly noises coming out of it. All I can think is that when we were putting the axleshaft 4wd engagement side back on, something slipped out of place. There a spring and shaft in there, with a collar that pulls a wheel up against a gear that engages the inner axle stub. Something must have slipped during installation. I only hope nothing got broken when I engaged it and was trying to figure out what the hell the noise was.
I was so convinced that noise was front diff as opposed to wheelbearing, especially since the front diff was empty, I've had one go before and other people say they're very common. My 02 Denali sounded exactly the same, I actually had the place I bought it from change the wheelbearings, no difference until I had the front diff replaced with a rebuilt unit. When we cracked this one open, the new oil I had added last week was totally trashed, filthy sludge. But none of the bearings looked really wiped out, worn but I was expecting to see at least one totally trashed.

But the sound (in 2wd) hasn't changed at all. I rotated the tires, hand checked the wheelbearings, I don't know what else it could be, maybe a u-joint or something? If it is a wheelbearing I'll be surprised, because normally wheelbearings are distinguishable when you turn the steering wheel. Got to run it 2wd for a week, next weekend I'm going to put it up in the air and run it to try to figure out where the noise is coming from. After fixing the 4wd problem that is.

One last thing, when I was rotating the tires after a test drive, I noticed the rear brakes were noticeably warm, and the fronts weren't. What could that mean? I changed all pads and rotors about 6 months ago, they work good. The e-brake inside the rear rotor wasn't on, maybe something failing/binding in the back? The noise sounds like it's up front though.

 

[stacks04]

okay, first off, your passenger side axle housing. on the shift collar assm more specifically on the axle shaft you have the spring clip, the gear, and then there is supposed to be a washer that is used as a thrust washer between the gear and the stubshaft that goes into the diff side gears internally. this may have fallen out and could be your noise.

second, the bearings that came out of the diff, specifically the 2 side bearings and the pinions, how did they look? the bad ones are usually very bad. the races are chunked and the rollers have either chunks missing or chunks "welded" to them from the races.

the noise could be transfer case, could be but unlikely an axle. could be tires, could be front hubs. i have a ford i am working on that i could not make the noise go away turning the wheel. only one hub was bad.

 

[Detroit Dan]

I did put the washer back in, but I'm wondering if something may have slipped out of place during reinstallation. As for the bearings, the pinion bearing showed some wear, the needle bearings in the axle tubes were a little noisy turning them by hand, compared to the new ones, but nothing was really obviously bad. I was expecting to see destroyed bearings and they just weren't that bad. So I probably spent all weekend tearing down and rebuilding this, spent over a hundred on bearings and races, and the end result was screwing up the 4wd. Makes me feel kind of stupid.
I'm really leaning toward wheel bearing hubs now, since the noise is so consistent. I guess the empty front axle faked me out, but it's probably a good thing I got it done before that failed and blew up due to lack of oil. I still can't believe that wasn't it. Everyone told me they are common, plus I went through this with my 02, and after changing wheelbearings didn't fix it, a new front diff did. And the noise is the same.
I did rotate the tires, no difference whatsoever. One reason I think it's front wheelbearings now is in listening to it, the noise actually gets louder just as your coming to a stop. I think that's because when you are braking much more weight is getting transferred onto the front wheels.
So this weekend the front axle will be coming apart again to fix that problem, I am so hoping I didn't damage something.
Next will probably be wheelbearings.

 

[Detroit Dan]

Well, pulled it apart and found the pinion was wicked loose. You could grab the yoke and shake it about a half inch. Well, probably a quarter inch. And we didn't forget to tighten it, we cranked it tight then backed off until it turned just barely freely. So, everything inside looked fine, all washers and springs and 4wd stuff intact. Tightened the pinion up, took it for a ride, came back and it was loose. Couldn't figure out what was going on, seemed like we had it seated right, but then driving the truck loosened it somehow. But the nut wasn't backing off or loosening itself, so it's like a press-fit issue. Tightened it again and it's tight enough now I guess but still making a pretty good hum in 4wd. Ran out of time so going to leave it for now. I figure the noise will either get a little quieter as things wear in, or it will get worse and something will fail. I found a place not too far away with a takeout front axle for $250, wish I'd just done that in the first place. Although I still would have been pi55ed about the noise not going away.
At least then the 4wd would have been working. With all the noise it made last week after putting it together the first time, I told her not to use 4wd. So of course it snowed, and the truck ended up getting stuck and getting a big scrape and dent in the door...

So is there some special secret about tightening the pinion nut? Everything I've found in writing detailing the installation just says "reinstall pinion nut". Thanks for all the detail.

 

[stacks04]

well first off, the pinion is a preload setup. i hope you have the crush collar in there? second on assembly you need to tighten and crush the collar to the right spec the first time without going beyond it. if you dont go far enough and the yoke is not quite tight enough then you could zip it a bit more with the gun, but if you go to far you cant just back off. the collar is crushed and no longer is applying the proper load to the bearings. if you really went to far then backed off to get it feeling right you will need to take it out and replace the crush collar again and retorque it properly.

 

[stacks04]

here is a quick blurb on it. usually i do it by feel, is i have done enough of them to know it. usually i will go just a tad tight and give the gear a good whack with a hammer and bronze punch. it usually seats the bearings and loosens things up just a tit.


Tighten the pinion nut until the pinion end play is just taken up. Rotate the pinion while tightening the nut to seat the bearings.

1. Measure the rotating torque of the pinion using an inch-pound torque wrench.Specification
   The rotating torque of the pinion should be between 1.0-2.3 N·m (10-20 lb in) for used bearings, or 1.7-3.4 N·m (15-30 lb in) for new bearings .
2. If the rotating torque measurement is below 1.0 N·m (10 lb in) for used bearings, or 1.7 N·m (15 lb in) for new bearings, continue to tighten the pinion nut.Tighten
   Tighten the pinion nut, in small increments, as needed, until the torque required in order to rotate the pinion is between 1.0-2.3 N·m (10-20 lb in) for used bearings, or 1.7-3.4 N·m (15-30 lb in) for new bearings.
3. Once the specified torque is obtained, rotate the pinion several times to ensure the bearings have seated.Recheck the rotating torque and adjust if necessary.

 

[Detroit Dan]

Stacks, thanks so much for the detailed info, thats what I had been looking for last weekend and couldn't find. I did install the crush collar, but we had to re-use the old one as we simply could not source a new one anywhere on the weekend. We did however find a mechanic who assured us he has re-used them many times without a problem.
Not sure when I might tear into it again, but I will print this and get a new crush collar before I do.
Thanks!

 

[THEFERMANATOR]

Stacks, thanks so much for the detailed info, thats what I had been looking for last weekend and couldn't find. I did install the crush collar, but we had to re-use the old one as we simply could not source a new one anywhere on the weekend. We did however find a mechanic who assured us he has re-used them many times without a problem.
Not sure when I might tear into it again, but I will print this and get a new crush collar before I do.
Thanks!

He fed you a line of BS then. You NEVER re-use a crush sleeve if you can help it, and if you do you MUST add a shim in so that you can crush it some more when you tighten it down. And if you back off because it's too tight then you have to start over as it WILL ruin the crush sleeve and wipe out the ring and pinion set if you run it that way. My neighbor learned this lesson the hard way in his stock car when he tryed building his diff for the first time. After that he had me come over and show him how to set one up.