Rear Differential 2015 Silverado Z71 Binding

[2015SSilverado]

Rear Differential 2015 Silverado Z71 Binding

 

Seems that the rear wheels try to turn at different speeds while driving straight on level ground. Intermittently can cause light, but immediately noticeable pull of steering wheel toward right.  More often occurs from stop during sharp turn to enter traffic at an intersection. Might continue pulling for 1/4 mile to 5 miles.  Sometimes does this on highway at 70 MPH. 105K miles on vehicle.  Yesterday, rear wheels were screeching lightly as I drove around traffic circles or turned at an intersection.  Are there any preferred lube and additive for the rear differential other than the 75w 90 and limited slip additives?  

 

Edited September 7 by txab

[txab]

Have you ever serviced this diff?

 

 

You use NO ADDITIVES in a G80.

 

I prefer Amsoil's Severe Gear 75w-90 with no issues. It comes in a handy squeeze pack

 

Some have used Mobil 1

 

You need to open up the diff and take a look inside to see whats going on

 

Edited September 7 by txab

[Black02Silverado]

I agree with txab, you needed to take the cover off and look inside.  Before you do that take the fill plug out and see what the fluid level is at. Also after driving is the rear cover warm or really hot? 

 

You will not know until you open it up for the most part.  If you are interested in the AMSOIL Severe Gear oil let me know, I can get you a quote.  Or if you just want to order you can order it here. 

[2015SSilverado]

On 9/6/2024 at 6:19 PM, txab said:

Have you ever serviced this diff?

 

 

You use NO ADDITIVES in a G80.

 

I prefer Amsoil's Severe Gear 75w-90 with no issues. It comes in a handy squeeze pack

 

Some have used Mobil 1

 

You need to open up the diff and take a look inside to see whats going on

 

Great feedback on my differential.  Thanks so much txab for the AMSOIL product referral.  It has not been serviced before to my knowledge.  It is a 12 Bolt diff with Service Parts Codes for G80 (diff) and GU6 (3.42 ratio).  Drained and measured 2.5 Quarts (give or take an ounce) of fluid without metal particles or flakes.  There was a light residue inside of the cover (dark gray in color) which wiped off easily with paper towel.  Ring gear showed no apparent scuffing, chipping, or cupping.  Good initial impression.  It is a PosiTrack diff with slip modifiers already in the lube, right?

 

You mentioned, "You use NO ADDITIVES in a G80."  So does the AMSOIL Already have the needed friction modifying additives?  Please advise if there is any issue with the additives already in it per the spec sheet for AMSOIL Severe Gear 100% Synthetic Gear Lube regarding use in the G80 diff.  I very much appreciate your reply and suggestions.  If the Mobile 1 use seems better would it require additives?

 

Any torque spec for cover bolts?  I've seen various statements from uncertain applications from 25 ft pounds to 20 ft pounds + 20% turn.

 

Capacity and fill is still unknown, but my impression was somewhere around 3 quarts.  Should it be filled to the bottom of the fill hole?  Some systems might be about 1/2 inch below the bottom of the fill hole.

[txab]

The point is the G80 doesn't need added friction modifiers. You can find such products on the shelf. Additional FM will cause issues.

 

a quote from one of the lubrication professionals on this site:

 

"Every GL has friction modifiers. Limited Slip or posi-traction differentials may have friction modifiers that reduce and increase friction for lock up or clutch lock-slippage. "

 

So again your GL may list it has some FM in it. The key is not to add additional FM to it. Some Diffs require it, the G80 locker does not.

 

You specifically asked about the M-1, no, no additives needed

 

Level of fluid? Yes most list a distance below the fill hole. On my 1/2 ton 2004 it's listed at 1" below. A lot of people fill it to the hole level. I've got mine filled barely below the hole right now.

 

if you  go below the hole, you can use a bent allen wrench or a pipe cleaner like kids have or a piece of stiff wire, all bent 90* on the end. They will show your depth.

Do you have the Owners manual for the truck? It often lists the fluid level desired. You can find the OM online if needed

 

3 qts for rear will do. Black02Silverado is a great source of info as he is a Amsoil dealer and helps sponsor this site. I buy all my products through him.

 

Don't forget your front diff if equipped. Same fluid in both ends.

 

As for torque value? I just know when it's tight. I just use a 3/8" ratchet and tighten. You snug it up, it's not coming out. 20ish lb ft will be fine

 

Edited September 9 by txab