Differential fluid

[CAJUN C4]

So what's a person with no mechanical expertise to do?
wait, I bet you're going to say "learn how, or pony up the cash to the dealer"
Is changing the rear dif. fluid difficult (let's assume I can talk my mechanically inclinded husband into helping me)?

I have a similar situation mine is called getting old...
I made friends with a couple local fellow Vette owners who are cinsiderably younger than myself. I pay them to help me or even to do everything I need done. Works out quite well

 

[c4c5specialist]

HI there,
LETS BE VERY CLEAR!!!!
First, a Trailblazer SS differential is a Zexel Torsen and should NOT be confused with the Getrag unit in Corvette.
I can give 7 instances of lubricants being used with supposed frictional modifier already in them which create clutch distress within the differential because of unpredicatable reaction when limited slip engagement is needed.
Cracked belleville washers are also a byproduct of overheating of the clutches.
While you can use any lubricant meeting the specifications listed in your owners manual, the frictional modifier SHOULD ALWAYS be used, NO MATTER WHAT!
Allthebest, c4c5

 

[jcs712]

HI there,
LETS BE VERY CLEAR!!!!
First, a Trailblazer SS differential is a Zexel Torsen and should NOT be confused with the Getrag unit in Corvette.
I can give 7 instances of lubricants being used with supposed frictional modifier already in them which create clutch distress within the differential because of unpredicatable reaction when limited slip engagement is needed.
Cracked belleville washers are also a byproduct of overheating of the clutches.
While you can use any lubricant meeting the specifications listed in your owners manual, the frictional modifier SHOULD ALWAYS be used, NO MATTER WHAT!
Allthebest, c4c5

Great post and timely to. I just changed out the rear diff fluid this past weekend and used the RP MaxGear 75W90 synthetic with friction modifier already added. Whole porocess was pretty simple if you have a set of ramps and a good allen wrench set. After reading many posts on another forum I debated on whether to get the GM friction modifier and add it knowing this product already had it incorporated. I decided not to add it as I was afraid I might be putting too much of the modifier into the mix. I was able to get about 1.6 quarts of the RP in the diff before it spilled out the fill hole. Does this seem about right? Will I be okay without the GM modifier? How much modifier do you add to a typical diff fluid change?

In any event, the reason for the change was due to some low level noise I was getting at high speed when pulling the wheel to the right. Sounded like a tire rubbing an inner fender well. I figured it was the rear diff. Fluid was changed 2.5 - 3 years ago at the dealer when the tech accidentally drained it when I requested a MN6 fluid change to Red Line D4 synthetic. He replaced the GM fliuid at no charge but I am not sure what he put in there since he did not document it. Mistake on my part. Always, always get this kind of stuff documented. With the new RP fluid in the noise seems to be gone. I will know more today once I am able to drive it for some distance. Car only has 11,665 mi on the odometer. Wih the kind of noise decribed above, do you think I have bigger issue looming or was the diff just letting me know it was time for a fluid change? Thanks for your input.

 

[CAJUN C4]

Redline with the modifier in it is also highly rated...........

How about Amsoil?

 

[Vettepirate]

Good thread, im happy it resurfaced, otherwise i wouldnt have known about the frictional modifier!

Does anyone know what would constitute old/dirty tranny fluid? Since im assuming it doesnt darken due to carbon and the like, what should i look for to tell me it needs to be changed?

 

[CAJUN C4]

A good rule of thumb would be about every 30K Miles or so.

 

[99WhiteC5Coupe]

Good thread, im happy it resurfaced, otherwise i wouldnt have known about the frictional modifier!

Does anyone know what would constitute old/dirty tranny fluid? Since im assuming it doesnt darken due to carbon and the like, what should i look for to tell me it needs to be changed?

I recently change the rear differential lube on my C5 (purchased new) after 45,000 miles. I drained the fluid into a clean pan, then into a "see-through" plastic jug.

The old fluid was dark, but not like dirty oil. The new GM lube was honey color.