Aztek Rear Differential on the AWD--Need Help!

[Brock Samson]

Yes, I know it's not 4x4, but I figured this was closer than off-topic.

Anyway, at parking lot speeds, the rear differential moans/groans. Sounds just like a power steering pump that is low on fluid, or that annoying nasal sound your little brother makes to torment you (ANNNNNNNNNNNNNNHHHHHHHHHHHHHHH). I haven't checked the fluid level yet, but I've read that this is a very, very common issue. Does anyone have any technical insight into what causes the groan? There is no clicking, cracking, knocking, whining, etc, just a groan. I haven't read anything useful yet on the subject. It appears Versatrak fluid is the only replacement for the fluid. So far, replacing the fluid is the only remediation I have seen. If that's the case, then ok, but it would seem like there is something else at work unless the fluid wears prematurely.

Fstop? PartsGuy? Thanks!

[Robo]

More of the same Aubs......
PM me the last 8 of your VIN

The only other thing I dug up is if the fluid has been contaminated by water. Been puddle jumping lately?



2004 Pontiac Aztek - AWD | Aztek, Rendezvous (VIN A/B) Service Manual | Transmission/Transaxle | Document ID: 686098
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Noisy on Turns
Cause
Correction

DEFINITION: A noise is present only when the vehicle turns.
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Inspect for the proper gear oil levels prior to performing system diagnosis. Refer to Lubricant Change .

Operate the vehicle turning in tight circles in both left and right directions. A moan, groan, chatter, or a pulsing type concern may indicate a pump, valve, or clutch pack malfunction within the differential assembly.
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Worn or loose rear differential mounts
Repair or replace as required.
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Loose torque tube bracket or a damaged bracket bushing
Tighten the bracket bolts or replace the bracket as required.
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Worn axle shaft constant velocity joints
Replace the constant velocity joints as required.
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Worn wheel bearings
Replace the wheel bearings as required.
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Incorrect type fluid

Installation of the incorrect type gear oil may create a "moan" type noise within 7 770-25 900 km (3-10,000 miles). Fluid that is "black" in color is to be considered normal and is darkened by the carbon material in the clutch plates.
Replace the rear differential assembly as required.

Fluid replacement will not correct a "moan" condition caused by the use of incorrect oil. Refer to
Differential Replacement .
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Worn clutch pack friction discs
Replace the differential assembly.

[Charles Helm]

Fluid replacement will not correct a "moan" condition caused by the use of incorrect oil. Refer to
Differential Replacement.

[Robo]

So what's the prognosis there Aubs?

[Brock Samson]

Well, I got the fluid. $25/16.9 FL OZ. Takes 4 bottles. I'm going to do the service later this evening. I hope this fixes the problem. Thanks for your help with the TSB.

Also, no luck on your suggestion of removing the back cover to have a look-see: Apparently, there are two parts for the rear differential. The fluid and.... THE REAR DIFFERENTIAL! There are no serviceable components.

Sometimes I do hate GM.

This vehicle also has some very expensive replacement parts. I could be building a nice trail rig if I replaced the rear diff ($1,789), transmission ($1,704), and transfer case ($1,491).

[Brock Samson]

Well, I changed the fluid (which has to be some of worst smelling stuff ever, BTW), and then proceeded to drive the vehicle in circles until I was thoroughly disoriented.

The groan is harder to hear now, but is still there to an extent. I will give it a week or so and see what happens. I've heard many reports on the Aztek Fan Club (yes, such a thing does exist) that it can take a couple days to go away.

I suppose if it remains, I'll just ignore it until the rear differential gives up.