Help me pick a Diff Fluid, 23 GMC Sierra 1500 AT4

[BobsArmory]

Looking to swap out the factory fluid in my trucks front and rear diffs.

2023 GMC Sierra 1500 AT4 3 liter Duramax
Factory Specs
Front: 75W-85 Dexron Low Viscosity ACDelco part #10-4122
Rear: 75W-85 High Efficiency Synth Hypoid Gear ACDelco part #10-4091

I was thinking of using something like 75W-90 Amsoil Severe Gear or HPL Differential Life 75W-90 but was wondering why they specify 2 different fluids. One has a friction modifier and the other doesn't? GL4 and GL5?

What are your thoughts?

 

[Bighorn2500]

Looking to swap out the factory fluid in my trucks front and rear diffs.

2023 GMC Sierra 1500 AT4 3 liter Duramax
Factory Specs
Front: 75W-85 Dexron Low Viscosity ACDelco part #10-4122
Rear: 75W-85 High Efficiency Synth Hypoid Gear ACDelco part #10-4091

I was thinking of using something like 75W-90 Amsoil Severe Gear or HPL Differential Life 75W-90 but was wondering why they specify 2 different fluids. One has a friction modifier and the other doesn't? GL4 and GL5?

What are your thoughts?

Does the rear have a limited slip differential? Typically LSD’s get the friction modifier.

Either of your choices are both very good options.

 

[BobsArmory]

Does the rear have a limited slip differential? Typically LSD’s get the friction modifier.

Either of your choices are both very good options.

It does have a locking rear diff.. As I recall it has an Eaton Locker but I cannot be sure at this time.

 

[mr_boring]

I know people will disagree, but if you are just driving it, use whatever. If you tow often or heavy, use a heavier weight. You can't go wrong with either of the ones you are looking at. I use Valvoline 75/140 because it's inexpensive and I love the flex fill packs (which Amsoil probably invented). I very rarely tow but old habits die hard.

 

[BrendanC]

HPL differential life 75w-90
amsoil severe gear
any syn off the shelf gear oils

^^^my order in picking differential oil. my uncle runs a fleet of tractor trailers and tractor trailer wreckers and he swears by the Amsoil severe gear so i rate the HPL and amsoil very close.

 

[proffittmarke]

I have the 2022 Sierra and put AMSOIL Severe Gear 75W90 in front & rear differentials. Works well.

 

[Snagglefoot]

It has nothing to do with limited slip differentials. It has everything to do with GM trying to get a bit more gas mileage by lowering the viscosity of the front diff fluid as typically the front diff is not used as much in four wheel drive. Have a look at the product information page.

 

[4WD]

It has nothing to do with limited slip differentials. It has everything to do with GM trying to get a bit more gas mileage by lowering the viscosity of the front diff fluid as typically the front diff is not used as much in four wheel drive.

Yeah - have done 5 GM’s now with 75W90 Delvac 1 …
Only my Jeep has ASG - those diff’s don’t hold much …

 

[barkingspider]

In my 22 gmc canyon, I got
Front: Mobil HD 80w90
Rear: Delvac 75w90

 

[proffittmarke]

Looking to swap out the factory fluid in my trucks front and rear diffs.

2023 GMC Sierra 1500 AT4 3 liter Duramax
Factory Specs
Front: 75W-85 Dexron Low Viscosity ACDelco part #10-4122
Rear: 75W-85 High Efficiency Synth Hypoid Gear ACDelco part #10-4091

I was thinking of using something like 75W-90 Amsoil Severe Gear or HPL Differential Life 75W-90 but was wondering why they specify 2 different fluids. One has a friction modifier and the other doesn't? GL4 and GL5?

What are your thoughts?

I’ve used Amsoil for 30+ years. Only problem was putting Amsoil 75W90 in rear diff. Made loud clicking noises when stopping. My rear is SU8 and does not like friction modifiers. I put the factory spec back in, then ordered Motul, works well in locking differentials, no friction modifiers.

 

[Silverado12]

FWIW the G80 rear in my 2012 Silverado doesn't use friction modifier either. I just use the cheap NAPA brand 80W-90 when it's on sale and change it every 25,000 miles.

 

[LDM]

Any good 75W90 will work just fine. You do not need friction modifier for LSD, the G80 in the trucks is a locking style rear end, no clutches.

I used Valvoline 75W90 synthetic in my front and rear when I changed out my diffs a few years ago on my 18 Sierra. Couldn't find the 75W85 anywhere for the front diff, not even the dealership had it in stock when I called. And they wanted an outrageous price for it as well.

 

[userfriendly]

80w140 synthetic in all my GM critters.

 

[BobsArmory]

80w140 synthetic in all my GM critters.

What GM critters do you have?

 

[meep]

My favorite has been amsoil severe gear at stock viscosity. I used to tow a lot and experienced some other brands draining out surprisingly thin after 50k miles. Amsoil goes out like it went in.

I also learned to stick with oem viscosity from some instrumented testing performed by 4x4 magazine years ago - thicker gear oils ran hotter, which is a problem towing - only run a 140 weight if there is a problem that the thicker weight solves. Transmissions are actively cooled … differentials are not.

 

[zuluplus30]

I’ve got probably 300k on various GM platforms all using almost exclusively Amsoil SVG 75w90, including my current ‘17 1500. The MPG difference between 75w85 and 75w90 is negligible at best. The G80 locker needs no friction additive, but any off the shelf lube that contains it works fine.

 

[Jerrysends]

Delvac was my choice.