[okeesignguy]

I am sure this has been discussed many times here but searching seems to only bring up older posts that don't really answer my question...

I have had my coupe for only a few months and have noticed that when I leave the house (before warm up) and I turn in my driveway or out onto the street the rear end makes a groaning noise...
It doesn't seem to do it after warm up and never when going straight...
My car is a 2011 with 71k miles on it...

My experience suggests to me that the fluid (gear oil) is either low or old and should be topped off or changed...
I also know that in the past, GM cars that I have owned need additives when fluid is changed but I don't know anything about these cars specifically...

If you know or have experience with this please give me some advise
Thank you!

 

[tinman]

Change your rear end fluid immediately and use the fluid with the additive.

 

[Padgett]

Use to be a posi needed a whale oil additive but not any more. If have G80 then look for a gear oil that says it is for limited slip differentials.

 

[okeesignguy]

Use to be a posi needed a whale oil additive but not any more. If have G80 then look for a gear oil that says it is for limited slip differentials.

I DO have a G80...
I see that a G80 is a limited slip diff..differentials...
Anything else special about it...?
I do have the FE3 option..is a G80 exclusive to that...?
Thank you...

Change your rear end fluid immediately and use the fluid with the additive.

Do you happen to know volume?
Thank you...

I'm sure everyone has their favorite brand to use I'm interested to know some opinions about that...
Also...there seems to be a lot of horror stories about even bigger problems after changing rear end oil...opinions?

 

[tinman]

Opinion? I gave mine. Change it with a quality brand name.

 

[okeesignguy]

Opinion? I gave mine. Change it with a quality brand name.

I know Sir...and I thanked you for it
Me asking for opinions was another question asked of everyone...

 

[tinman]

Understood. I'm willing to wager most folks will agree with me. Never hurts to ask! Folks here definitely have opinions, lol.

 

[Long]

I DO have a G80...
I see that a G80 is a limited slip diff..differentials...
Anything else special about it...?
I do have the FE3 option..is a G80 exclusive to that...?
Thank you...

G80 is NOT exclusive to FE3.

 

[okeesignguy]

G80 is NOT exclusive to FE3.

Thank you...after some research I now realize that...GM uses them in lots of apps...

 

[silversport]

check your owners manual for type and amount to use...if you don't have an owners manual they are available free online...good luck and congrats on having the G80...many here do not have that option

Bill

 

[okeesignguy]

check your owners manual for type and amount to use...if you don't have an owners manual they are available free online...good luck and congrats on having the G80...many here do not have that option

Bill

Thanx Bill... I see now that it takes 2.3 pints...

 

[okeesignguy]

Looking around here on the forum for more info I am seeing posts that say NOT to use synthetic....GM does not recommend it but rater recommends GM P/N 88862624...

 

[rsingl]

Fortunately the differential is easy to change in modern vehicles. Be sure and wipe the fill and drain plugs while they are out, one or both are magnetic but it has been too long since I owned my CTS to remember.

GM's current LS ready axle lubricant is:

DEXRON LS Gear 75W-90 (GM Part No. 88862624, in Canada 88862625)

No it isn't cheap but it is what was formulated specifically for the clutch makeup in your axle which has already been somewhat abused by fluid that is depleted. There is no need to experiment with fluids, use what was designed for this specific application.

I recently ordered a fairly expensive Kubota 72" front deck commercial mower and I am amazed at the number of owners posting looking for alternatives to Kubota hydraulic fluid to save a few bucks on fluid going into a $20K mower

Rodger

 

[okeesignguy]

I am finally getting around to doing this and I am realizing that it takes 2.3 pints...
It is sold by the qt...which is 2 pints...
So...I hafta buy 2 qts just to get that extra .3 pint...! Are you kidding me!?! Lol

 

[Lifespeed]

Looking around here on the forum for more info I am seeing posts that say NOT to use synthetic....GM does not recommend it but rater recommends GM P/N 88862624...

Not sure why synthetic would be verboten, diffs are diffs, with the usual caveats of friction modifier (included in Redline oil) if one has a clutch-type LSD. I like Redline for diffs, but like most oil discussions any good-quality lube will work. I would not use the "shockproof" variant for a clutched diff, but it's great for high-horsepower boat V-drives.

 

[Padgett]

Synthetic can make a posi slip like crazy.

 

[Lifespeed]

Synthetic can make a posi slip like crazy.

Never experienced that. Worn clutches sure will make a posi slip, they do have a finite lifespan.

 

[okeesignguy]

So...I hafta buy 2 qts just to get that extra .3 pint...! Are you kidding me!?! Lol

 

[Padgett]

Had a GM spec at one time that said 25 lb-ft differential could make a good posi slip. Could check with a torque wrench. Is why lockers were popular.

 

[Lifespeed]

Had a GM spec at one time that said 25 lb-ft differential could make a good posi slip. Could check with a torque wrench. Is why lockers were popular.

When up on jack stands in a static condition, yes. When under a load from engine torque * gear ratio, the side gears spread and load the clutches. The breakaway torque is far greater under these conditions. 25lb*ft would be useless in a dynamic condition.