Saab 9-7x G86 LSD Rear Differential shudder

Nathan 9-7x

Member
Hey gang! I have an '06 Saab 9-7x with the 5.3 V8, and 88K miles. Recently I've noticed a shudder coming from the rear driver's side tire. It does not bind or crow hop, it's just a shudder. It occurs when normally accelerating from a stop turning almost any degree. I changed my encoder motor 7 months ago, a gear inside had broken causing it to bind up, which made the driveline bind up and crow hop on full lock turns. I've removed the encoder motor completely, didn't notice a difference, but I'll have to recheck that this week, I'll update. Yesterday I changed the rear diff fluid using Mobil 1 synthetic LS 75w/90. Afterwards I drove in figure 8's and donuts. I can still feel a shudder.

Here's some more driveline info. 7 months & 7K miles ago when the encoder motor broke, the front diff. inner seal started to leak. I drained and removed the front diff. from the oil pan enough to pry the old inner seal out and press the new seal in. I replaced both seals (genuine GM), intermediate shaft and axle disconnect (genuine AAM) just as preventative maintenance since I had everything apart. Of course I had to refill the front diff, but decided to change the rear too. I used Mobil 1 Synth LS 75w/90. However - at that time I added the GM Limited Slip additive to the rear diff. because it was "recommended" by the parts counter guys. I've replaced the transfer case fluid using AutoTrakII about 15K ago.

In searching the forum for help, someone had posted a GM bulletin saying the G86 did not need the LS additive. Does anyone know if this shudder could be caused by this additive being used in conjunction with the Mobil 1 fluid? Too much LS friction modifier?
Thanks again gang! I appreciate it!
 
I don't know where you got that information but the G86 does require the additive. I have been through the same thing with mine and the only thing that got rid if the shudder and noise was the GM limited slip fluid.

http://www.amazon.com/ACDelco-10-4034-Dexron-75W-90-Gear/dp/B008BZS6J8

You need 3 quarts and the additive is already in the fluid. This is the recommended fluid and it worked great in mine.
 
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Nathan 9-7x

Nathan 9-7x

Member
Found the document I was talking about! :2thumbsup:

xTooltipElement
Service Information
Document ID: 2084198
--------------------------------------------------------------------------------

#08-04-20-002: Jerk/Jump Sensation with Growl/Groan Noise, Shudder, Bind From Rear of Vehicle While Turning (Drain/Refill Rear DifferentialFluid) - (Mar 19, 2008)


Subject: Jerk/Jump Sensation with Growl/Groan Noise, Shudder, Bind From Rear of Vehicle While Turning (Drain/Refill Rear DifferentialFluid)


Models: 2006-2008 Chevrolet TrailBlazer SS

2005-2008 Saab 9-7X

2008 Saab 9-7XAero

with Limited Slip Differential(RPO G86)




--------------------------------------------------------------------------------

Condition
Some customers may comment on a jerk or jump feeling accompanied by a growl/groan noise, shudder or bind from the rear of the vehicle while turning.

Cause
This may be caused by slip/stick of the posi-traction clutch plates. As plates slip and stick, a jump or jerk feeling occurs accompanied by a growl or groan noise.

Correction
Remove the rear differentialfluid using the procedure provided in SI.
Important: DO NOT add any limited-slip additive (friction modifier). With this new fluid (DEXRON® LS Gear Oil 75W-90), it is no longer required to add friction modifier. If a friction modifieris added, it will cause the fluid to lose some of its friction reducing properties as well as reducing seal life.

Fill the differential with DEXRON® LS gear oil, P/N 88862624 (in Canada, P/N 88862625).
Follow the procedures in SI for the 8.6 in axle on the Saab 9-7X4.2L and 5.3L models. The lubricant levels should be between 0 mm to 10 mm (0 in to 0.4 in) below the fill plug opening.
Follow the procedures in SI for the 9.5 in LD Axle on TrailBlazer SS and Saab 9-7XAero models. The lubricant level should be between 15 mm to 40 mm (0.6 in to 1.6 in) below the fill plug opening.
Once the differential fluidis changed, the vehicle must be driven in 8-10 tight figure eight maneuvers to allow the fluid to be worked into the clutch plates.
Important: If the noise condition is improved by this procedure but is not completely eliminated, it may be necessary to perform the procedure a second time.

Notice: There will be some vehicles where the damage to the clutch packs from wear or moisture will be too extensive to be fixed by this procedure. In this case, replace the rear differentialcenter section (differential gear case), which includes clutch plateand springs.

Parts Information
Part Number
Description
Qty

88862624 (US- 1 Quart)
DEXRON® LS Gear Oil
2.7 Quarts

88862625 (Canada- 1 Liter)
DEXRON® LS Gear Oil
2.6 Liters


Warranty Information (Excluding Saab U.S. Models)
For vehicles repaired under warranty, use:

Labor Operation
Description
Labor Time

F9709*
Drain and Refill Rear Axle Fluid
0.4 hr

*This labor operation number is for bulletin use only. This number will not be published in the Labor Time Guide.


Warranty Information (Saab U.S. Models)
For vehicles repaired under warranty, use:

Labor Operation
Description
Failed Object
Fault/Reason Code
Location Code
Warranty Type
Repair/Action Code
Labor Time

4731104*
Drain and Refill Rear Axle Fluid
47311
10
0
01
05
0.4 hr

* This labor operation number is for bulletin use only. This number will not be published in STM.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION


© 2010 General Motors. All rights reserved.
 
That's exactly what I was saying. This is referring to the new recommended fluid that I showed you. It is saying that the friction modifier is already in the fluid and not to ad any more to it. But it is absolutely necessary to use this fluid.

Many other brands have been tried, but this is the only one that makes it correct. GM Magic fluid lol
 
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Nathan 9-7x

Nathan 9-7x

Member
I've used Mobil 1 Synth LS 75w/90 fluid since it was new. Changing both front and rear once every summer. Shortly after I added that LS additive is when I started having this issue.
 
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Nathan 9-7x

Nathan 9-7x

Member
When I did the fluid change I noticed it was much improved. Especially after doing the figure 8's. I wonder about the LS clutch packs. If they're worn or if the center section needs to be replaced. I'm going to drive it with this fluid till this full tank of wonderfully inexpensive gas is empty then drain and refill with the GM Dexron LS stuff.
Thanks for the help BlazingTrails! :2thumbsup: I'll keep the thread updated.
 

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