Rear Axle Fluid Change.

SandShots · August 27, 2008

I own an 05 silverado 1500 HD 4x4

It's time to draing and fill the rear axle. The manual calls for 75x90 Synthetic.

How many bottles do I need to buy and what type? Im not gonna use the GM brand. Going to the local autoparts store. Also, do I need to add a tube of that friction modifier?

thanks.

MS3DALE · August 27, 2008

No...DO NOT ADD any friction modifier.

Three bottles should be enough.

2500HD 8.1 · August 27, 2008

I use Mobil 1 and it takes about 2.5 quarts.

C & A s Dad · August 28, 2008

Fill it until the oil is approx 5/8" below the fill hole. You do not want to fill it until it runs out of the fill hole. This can cause leaks at the rear wheel seals.

Be sure and remove the fill plug before you remove the rear end cover. Sometimes the fill plug strips and cannot easily be removed and if you have already removed the rear cover, you are in trouble.

I find that a good quality 3/8" drive pull handle that has square corners works best. It gets a better bite than a ratchet or extension that has rounded corners.

SandShots · August 29, 2008

i think my axle also has a drain plug. so ill drain and fill without pulling off the diff cover.

the freakin dealer said i had to use the friction modifier.

why or why not should i use it?

Paul58 · August 29, 2008

I upgraded my rear diff cover to a larger capacity cove and added 75W90 full synthetic oil and friction modifier. My son-in-law assisted with this mod and he has access to the GM shop manuals which listed the friction modifier as being required with my rear axle (3.73 mechanical locker). He said normally the friction modifier is required if you have the Limited Slip or Mechanical Locker rear axle. Everything has been working great since this mod, and my rear end is running much cooler when towing!

Won_Hunglo · August 29, 2008

Everything has been working great since this mod, and my rear end is running much cooler when towing!

What are your before & after temps?

dlstewart01 · August 29, 2008

I upgraded my rear diff cover to a larger capacity cove and added 75W90 full synthetic oil and friction modifier. My son-in-law assisted with this mod and he has access to the GM shop manuals which listed the friction modifier as being required with my rear axle (3.73 mechanical locker). He said normally the friction modifier is required if you have the Limited Slip or Mechanical Locker rear axle. Everything has been working great since this mod, and my rear end is running much cooler when towing!

General Motors says that a friction modifier is NOT required for a G-80 locker. It is only required for a true limited slip which was only offered in the quadisteer as a G-86.

Have a good one,

Don

MS3DALE · August 29, 2008

I upgraded my rear diff cover to a larger capacity cove and added 75W90 full synthetic oil and friction modifier. My son-in-law assisted with this mod and he has access to the GM shop manuals which listed the friction modifier as being required with my rear axle (3.73 mechanical locker). He said normally the friction modifier is required if you have the Limited Slip or Mechanical Locker rear axle. Everything has been working great since this mod, and my rear end is running much cooler when towing!

General Motors says that a friction modifier is NOT required for a G-80 locker. It is only required for a true limited slip which was only offered in the quadisteer as a G-86.

Have a good one,

Don

Yes,I've seen guys do damage to there rear-ends when they added the modifier and it wasn't required.

SandShots · August 29, 2008

I upgraded my rear diff cover to a larger capacity cove and added 75W90 full synthetic oil and friction modifier. My son-in-law assisted with this mod and he has access to the GM shop manuals which listed the friction modifier as being required with my rear axle (3.73 mechanical locker). He said normally the friction modifier is required if you have the Limited Slip or Mechanical Locker rear axle. Everything has been working great since this mod, and my rear end is running much cooler when towing!

General Motors says that a friction modifier is NOT required for a G-80 locker. It is only required for a true limited slip which was only offered in the quadisteer as a G-86.

Have a good one,

Don

the manual does say to use only on quadisteer axle, and doesnt say to use it on mine.

dlstewart01 · August 29, 2008

I upgraded my rear diff cover to a larger capacity cove and added 75W90 full synthetic oil and friction modifier. My son-in-law assisted with this mod and he has access to the GM shop manuals which listed the friction modifier as being required with my rear axle (3.73 mechanical locker). He said normally the friction modifier is required if you have the Limited Slip or Mechanical Locker rear axle. Everything has been working great since this mod, and my rear end is running much cooler when towing!

General Motors says that a friction modifier is NOT required for a G-80 locker. It is only required for a true limited slip which was only offered in the quadisteer as a G-86.

Have a good one,

Don

the manual does say to use only on quadisteer axle, and doesnt say to use it on mine.

Because you do not have a limited slip. The only truck that offered a limited slip was the quadisteer. The RPO code was G-86- limited slip. You have either an oped diff, or a G-80 Eaton LOCKER which does not require an additive.

Don