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99 AWD BadAstro
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Discussion Starter · #1 ·
1999 Astro CONVERSION VAN, fully carpeted/built inside with rear mattress/bed area
@101k purchased with rear end whine while under power, coast = goes silent. Gradually was getting louder and louder, so:
@105k decided to have rear end rebuilt w SKF Master Rebuild Kit, and G80 locker off ebay. This cost around $2k.

Result? Quieter, but not silent. I think my pinion was going out before, so I figured I'd rebuild it w high quality parts and upgrade to G80 locker.

Since being rebuilt, I have put on about 6k miles driving it to CO and back (2 times) , and man, it's getting bad again and idk what to do.
On gas even the SLIGHTEST BIT, it's WHIRRRRRRRRRRRRRRR and let off the gas, and poof, it's model 3 silent (by comparison). To be clear, the diff functions fine, and I've done a lot of research on this forum, and so many people just say "yeah it whines they all do" and man... there has to be something to do. My van is SUPER plush, with a thick carpeted interior and bed/mattress back there, and it's just so exhausting on longer drives, the sound isn't a bad sound, it's the literal amplitude.

If I take it back to the same shop, what should I even ask them to do? Tighten the pinion preload? Check wear pattern on gears? What should I be doing to get this thing quiet? Seriously it's driving me a bit crazy on longer days dudes, there has to be a way to get the rear end silent....
 

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2000 Lifted 4x4 Astro 92 V8-350 Shorty
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If I take it back to the same shop, what should I even ask them to do? Tighten the pinion preload? Check wear pattern on gears? What should I be doing to get this thing quiet? Seriously it's driving me a bit crazy on longer days dudes, there has to be a way to get the rear end silent....
IF????

If you take it back???
Why on earth wouldn't you take it back?
You paid top dollar to have it fixed, and it's clearly not fixed.
It also apparently WAS quiet AND got worse with time.

NO it should NOT be that noisy.. and apparently wasn't when first fixed.

What should you "ask them to do"???
Seriously???
Do you feel like you should need to direct them on how to do their job?
How about "FIX THE NOISE"
Let them figure out what they did wrong
 
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Common Sense + Critical Thinking
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If it's bad enough that it's annoying, there is something wrong. Take it back to them and have them fix it.
 

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2002 Astro LT RWD
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I have nothing concrete to add to the discussion/solution but my 02' RWD is experiencing a very similar issue. First noticed about 3 yrs/30k ago and has been getting steadily louder since. Seems to be worst right around 50 mph. Disappears completely if I let off the throttle. Hoping to upgrade to an 03-05 disc rear end in the near future for this and a variety of other reasons. I plan to have the used axle checked out beforehand by a qualified shop. I do almost all my own work but, like @ADDvanced, rear axle setup is out of my wheelhouse. Not something I'd want to 1st time DIY on a road-trip vehicle.

I completely understand the hesitancy to bring it back to the shop that appears to have done a subpar job. On the other hand, you likely have no legal recourse if you don't at least try to get it fixed by them. If they stonewall you (or fail again), I'd recommend finding a shop that works exclusively on ring & pinions. Not sure what's available in your area but you may have to search around. We've got several here in Metro Detroit but we're also a major hub for automotive mods etc.

Looking forward to hearing about the outcome on this one. Hope it's quiet for your next trip
 

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99 AWD BadAstro
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Discussion Starter · #7 ·
Update: I took my van back to have them double check the backlash on the pinion, thinking it was the pinion. The techs rode in the van a few times, and heard the whine. They drained the diff, checked it again, according to them everything seemed kosher. So they took it for another ride, and started thinking maybe the whining wasn't the diff, but the transfer case.

Now... given that my van just recently hit 100k, I assumed it had been serviced sort of recently (this was a dumb assumption) so I haven't touched it. Anyway, they drained my transfer case and instead of the blue auto track fluid, it was BLACK, with a lot of metal flakes. They filled it back up with some fresh AutoTrak 2 fluid (blue) and sent me on my way.

I drove the van 4000 miles over the holidays, and it whined the whole time but no issues. I guess... my question is... is there a way to narrow it down to the transfer case vs rear end? It sounds like the rear end, but it's hard to really say. Is there a procedure I could do which would definitively tell me it's the transfer case vs the rear end? Just because the fluid was black and there were some sparkles, doesn't have me fully convinced.

I am planning to replace it with a 2wd/4hi/lo case at some point, which may be sooner than anticipated.
 

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2000 Lifted 4x4 Astro 92 V8-350 Shorty
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Well the fact the fluid in transfer case is black with speckles is certainly suspect. Someone likely towed it incorrectly or drove it with mismatched tires and damaged the clutch packs... but that's speculation. The damage (if it's the case) could have spread internally... I'd say it's a "possibility".

If you had a manual case, you could pull the rear driveshaft and drive in 4-high, letting the front wheels pull you. But the rear would still be turning.. so this wouldn't prove anything, and the transfer case (and front differential) would still be turning too. Maybe someone else has a clever idea.

Certainly pinion/ring gear engagement can be measured, but even if correct, noise can still happen.

You'll certainly rule out the transfer case one day in the future when you switch it out.. lol
 
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Someone didn't shim the pinion and/or the carrier properly. Been there, had that done already. Sounds great for a day or two and then the nightmare starts. The problem is that the teeth of the pinion are not meshing with the ring gear where they are supposed to. Also could have used the old crush sleeve rather then installing a new one. It will eventually destroy the teeth on both gears. Many mechanics think they are so easy to do and actually they are IF YOU KNOW WHAT YOU ARE DOING !!!! Pinion depth into the ring gear is critical and if off will cause what you just described.

The black fluid in the transfer case is another story.
 

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Better shops have remote vibration/noise analyzers, so they can read them while road testing. But,like I asked before,was the ring and pinion replaced? They wear, and if run long enough with a problem, you will never be able to shim or adjust the noise away. Sometimes, running on Dyno or load plates make finding such a problem easy, as you can have someone under the vehicle. Heck,I have even had someone run wheels in drive,up on a hoist, while riding the brakes, to put a load on things. Yes, a bit hard on brakes, but it is not done for long.I guess we are losing lots in the field of intelligent new mechanics.
 

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2000 Lifted 4x4 Astro 92 V8-350 Shorty
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They wear, and if run long enough with a problem, you will never be able to shim or adjust the noise away.
I suspect you may "possibly" find this to be the case.
If it was setup incorrectly, then the bad wear may not be repairable, without replacing parts.

Good luck
 

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99 AWD BadAstro
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Discussion Starter · #12 ·
Ring and pinion gear were not replaced, my van only had 110k on it and they said they looked great. Idk what to do. I will try to find another rear end shop but there just are not many around.
 

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Most definitely Bob. Only two possibilities exist as you state the rear was completely rebuilt, but did not replace the ring and pinion.

First, since it was making noise before it was repaired, the bearings were definitely on their way out and possibly the ring and/or pinion as well. Whenever we rebuilt a rear with known issues, all wear components including the ring and pinion, are replaced. ESPECIALLY if the rear had known noise problems before. If the ring and pinion looked like new and showed no signs of irregular wear, they could be reused if on a budget. But for your $2000 they should have replaced everything

Second, is that when rebuilt, the pinion depth and carrier assembly were not shimmed correctly. The pinion teeth must be set up to contact in the center of the ring gear teeth for proper torque distribution in the gears. If not correct, the pinion either rides high or low on the gear and will wear incredibly quickly. We have seen the teeth actually broken off because people don't take the time to check. The carrier also has to be shimmed correctly to allow the teeth to make solid contact in the center of those teeth.

The bearings were replaced which lessened the noise the rear made, but as the pinion and ring gear begin to rapidly wear from not being set up correctly. Whoever rebuilt that rear should rebuild one more and then quit.

Either that of they forgot to put oil in it when it was rebuilt.

And NO they all do not whine. People say that when they don't understand the problem as to WHY they are whining.
 
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