Trying to change gear oil, confused...

[Daryl LBZ]

So my front axle has been howling at low speed wether I'm in 4wd or just 2wd. I've been wanting to change the fluids to Royal Purple anyhow so I'm going to change it. I looked in the owners manual and here's what is says:

 

Front Axle (1500 Series) - Four-Wheel Drive - SAE 80W90 Axle Lubricant

 

Then it says this:

 

Front Axle (1500, 2500 HD, and 3500HD Series) - SAE 75W90 Synthetic Axle Lubricant

 

 

1500 is listed in both lines so I have no idea which weight oil to go with? Can someone help me out? Thanks

[DaveH71]

either one is fine, i personally use 75w-90 synthetic

[Z45]

75W-90 is best. 80W-90 is not being used much anymore, 75W-90 synthetic is more fuel efficient and the best choice.

[Carder09]

I would use what the manual says. Why defer if it says use this in the front. If synthetic is not required, there is a reason I would think.

[MS3DALE]

Daryl,

 

80W-90 "non-synthetic" would be the correct fluid and weight,although 75W-90 wouldn't hurt a thing, There are two different specs for the two different front axles that 1500's use..the part-time 4wd (S4WD) and the full-time 4wd (F4WD)

...

 

Front Drive Axle (8.25” S4WD Axle)

 

 

SAE 80W–90 GL5 Lubricant

 

 

89021671

 

 

 

 

 

Front Drive Axle (8.25” F4WD Axle )

 

 

Synthetic Gear Oil

 

 

88900401

[Daryl LBZ]

Ok thanks for the info everyone. If I remember right I think the Royal Purple is 75W90 I'm going to try it out and see how it goes.

[Black02Silverado]

The Royal Purple will work well.

[jaredlucky16]

Theres a TSB to use 75-90

[Daryl LBZ]

Theres a TSB to use 75-90

 

 

 

Didn't see that anywhere? I put Royal Purple 75W90 in the front diff this morning, and so far so good. I ran it around the yard in 4wd and 2wd without it making any noise at all. Not really that many metal shavings in the fluid to be concerned about, but there was a little more than I expected. This weekend I'm going to get two more quarts and change the rear too.

[JaBradt85]

I need to do this on mine, I have had 5 qts of Mobil 1 75w90 for months. I did my transfer case about about 12k ago. I can't get the courage to take the cover off the back witht the brake line and bracket on the top bolt. Also is the gasket reusable?

[brainpause]

I need to do this on mine, I have had 5 qts of Mobil 1 75w90 for months. I did my transfer case about about 12k ago. I can't get the courage to take the cover off the back witht the brake line and bracket on the top bolt. Also is the gasket reusable?

 

 

Rear diff is the easiest one.

 

Get a new gasket. Make sure the mating surfaces are smooth. The old gasket in mine had gotten hard, so the Dremel carbon brush worked wonders.

[txab]

I need to do this on mine, I have had 5 qts of Mobil 1 75w90 for months. I did my transfer case about about 12k ago. I can't get the courage to take the cover off the back witht the brake line and bracket on the top bolt. Also is the gasket reusable?

 

 

Loosen the fill plug before pulling the rear cover

[Daryl LBZ]

I need to do this on mine, I have had 5 qts of Mobil 1 75w90 for months. I did my transfer case about about 12k ago. I can't get the courage to take the cover off the back witht the brake line and bracket on the top bolt. Also is the gasket reusable?

 

Rear diff is the easiest one.

Get a new gasket. Make sure the mating surfaces are smooth. The old gasket in mine had gotten hard, so the Dremel carbon brush worked wonders.

 

 

 

I'm not sure if I even need a new gasket for mine. If I remember it right I think I saw a drain plug on the cover the last time I was under the rear of the truck. I'm gonna take another look tomorrow and find out for sure.

[Z45]

Daryl,

 

80W-90 "non-synthetic" would be the correct fluid and weight,although 75W-90 wouldn't hurt a thing, There are two different specs for the two different front axles that 1500's use..the part-time 4wd (S4WD) and the full-time 4wd (F4WD)

...

 

Front Drive Axle (8.25” S4WD Axle)

 

 

SAE 80W–90 GL5 Lubricant

 

 

89021671

 

 

 

 

Front Drive Axle (8.25” F4WD Axle )

 

 

Synthetic Gear Oil

 

 

88900401

 

 

The reason for the 2 spec's is fuel economy and no other reason.

 

The S4WD front axle sees part time use and thus the non-synthetic 80W-90 is more cost effective and since GM says the front axle fluid NEVER needs replacing, they are saving money.

 

The AWD (Denali, Escalade, Etc) the front axle is always turning and the 75W-90 provides better fuel economy and better protection from excess heat.

 

This goes back a few years but will shead light.