05 Saab 9-7X Rear Differential LSD Failure GM G86

[dareo]

Friends SUV, 2005 Saab 9-7X aka most expensive Trailblazer variant, 5.3 V8. High miles over 260k, LSD started to not unlock and is acting like a spool or welded rear. G86 rear end, viscous lsd type, not the G80 mech locker. New fluid made problem worse, fluid did not have LSD add pack. Old fluid very dark black color.

Would you:

Get used rear end for few hundred bucks

Try adding LSD additive to new fluid, or try draining fluid for GM Dexron LS gear lube?

Possibly have it rebuilt somewhere. Friend doesn't have the skills to go into a differential. He could R&R the axle.

 

[CT8]

Take it to a shop.

 

[jeepman3071]

I'd first try adding fluid with the proper LSD additive, and go from there. If the new fluid doesn't work, and he can swap a differential, I'd get a used one out of a trailblazer or envoy for a 260k mile vehicle.

 

[dareo]

Fluid is Mobil Delvac synthetic 75w90 since i had 2.5 qts sitting around to donate to him. Money is tight for him but a shop did quote about 500 to rebuild the diff. Could we just get whatever LSD additive and put that in there with the delvac fluid?

 

[jeepman3071]

Originally Posted By: dareo
Could we just get whatever LSD additive and put that in there with the delvac fluid?


That should work fine.

A friend had a Ranger with an LSD in the rear. He put regular fluid in and it chattered and acted strange on dry pavement. New fluid with LSD additive fixed it. I believe he used Redline.

 

[Superflop]

Get it rebuilt professionally. Iirc when the viscous fluid leaks out of the assymbly it causes it to fully lock as opposed to free wheel or operate as if open. Doubt fluid will make any diff nor will the friction modifier (lsd additive) which it doesnt need.

 

[4WD]

Have had that Delvac synthetic in Canyon rear for a couple years - only it's a G80 ...
Has performed well ...

 

[dareo]

We are looking at a junk yard rear end since they like $200 and rebuild shops are like 500-600.

 

[Nick1994]

I'd throw a junkyard one in there.