Friction Modifier?

[Blk88GT]

I'm changing out the axle seals and doing some rear brake work on my dad's truck.

 

It's a 2004 GMC Sierra 1500, 5.3 4x4 extended cab with a 6600lb GVW.

 

I am not using GM rear end lube. Does this truck require friction modifier?

 

Thanks in advance.

[csheatz]

not sure why I bother to post because i am not sure about this, guess I am bored! But I think Mobil 1 75-90 gear lube is what is used.

[Blk88GT]

That's not what I'm asking. I need to know if this rear end requires friction modifier.

 

The manual states to use GM 75w90 lube only.

 

I am not using GM lube. I am using Castrol 75w90.

 

I need to know if I need to add friction modifier or not because I don't know if the GM 75w90 lube comes pre-charged with it. The Castrol does not.

 

Hope that clears up my question.

[Majorleaguebass]

ahhh and we see the light

[gvbhunt]

This is what Amsoil recommends for your truck.

 

Differential, Front .....GL-5

All Temps......80W-90

SAE 80W-90 Synthetic Gear Lube

Severe Gear 75W-90

SAE 75W-90 Synthetic Gear Lube

Standard Differential, Front Full time 4WD.....GL-5[4]

All Temps......75W-90

Severe Gear 75W-90

SAE 75W-90 Synthetic Gear Lube

Severe Gear 75W-110

Differential, Front Selectable 4WD.....GL-5

All Temps......80W-90

SAE 80W-90 Synthetic Gear Lube

Severe Gear 75W-90

SAE 75W-90 Synthetic Gear Lube

Standard Differential, Rear Others.....GL-5[4]

All Temps......75W-90

Severe Gear 75W-90

SAE 75W-90 Synthetic Gear Lube

Severe Gear 75W-110

Differential, Rear W/ QS4 Axle.....GLS[5][6]

Severe Gear 75W-90

 

None of which have an additive.

[Blk88GT]

Thank you, that's what I thought. I appreciate the quick answer, now if only the parts store can find the right axle seals I can get this thing off my hoist!

[csheatz]

ahhh and we see the light

 

 

light? wooooo where?

[Ranger]

Does the truck have a rear locking differential? It's called the G80 in your RPO list, that would be the only reason you'd need the friction modifer.

[dlstewart01]

GM says to use synthetic, and NO additive is needed for the G-80.

 

Don