75w90 recommendations for GM AWD

[HOG]

Hey guys, I'm researching gear oil for my Buick Enclave AWD. The vehicle has both a rear differential, and a transfer case (and some say it has a front diff too?? but i'm not sure?). Anyways, I'm in Toronto ONT, and am having a super hard time finding Amsoil which only has great reviews everywhere.... but again, I cant seem to find any. I also can't seem to find any Mobil 1 or Valvoline... so lets rule those out.

My local parts store does have Royal Purple, Castrol and Lucas.

Are there any reviews or recommendations about the above 3? What do you guys think for GM's AWD vehicles? Also, do I need to add anything to these when changing?

 

[MSTUEBER]

Just last month I used Valvoline 75w90 to replace the rear differential in my 1992 Miata.

 

[901Memphis]

Between the three you listed royal purple

 

[dlundblad]

I would find out if you for sure need the limited slip additive. If you're unsure, find one that has it just in case. It shouldn't hurt a thing.

Find the cheapest of the 3 you mentioned. Your results will be the same regardless of what you buy.

 

[barkingspider]

Of the 3 u listed, I like Castrol best.

 

[HOG]

Thanks for your replies guys,

Originally Posted By: dlundblad
I would find out if you for sure need the limited slip additive. If you're unsure, find one that has it just in case. It shouldn't hurt a thing.

Find the cheapest of the 3 you mentioned.


Regarding the limited slip additive - this I am unsure of and was hoping someone here could shed some light on that particular question. I was leading towards Royal Purple MAX GEAR, with Synerlec - which appears to indeed have some additives, but didn't want to get pulled in by all the hype of RP products (never used RP before). I'm familiar and satisfied with Castrol products, but if theres something better, I'll bite.

Price ranges from approx $17 to $25 up here in Toronto, RP being the most expensive at $25. AC Delco stuff goes for $20/L at my local dealership, but its a generic fluid, with NO description other than the GM part #.

I was also hoping to find out if the Lambda trucks from GM have a FRONT diff as that also seems to be up for debate.

 

[MrHorspwer]

There is no front differential. The transfer case (more appropriately described as a power take off) is just a helical gear on the transmission output shaft that drives a hypoid gear set. No differential.

For the rear differential, no limited slip additive is needed. The gear lube you're replacing does not interact with the clutches. The clutch is a sealed electromagnetic unit with no provisions for fluid service.

The AC Delco synthetic 75W90 (P/N 88900401) is a very high quality fluid made by Petro-Canada.

 

[charbaby]

The only 75W90 that I have ever used was Mobil 1 Gear Oil 75W90 LS(limited slip). I have used it in several vehicles and I really like it. I can't answer for any other brand. I have even used it in vehicles that DID NOT require the LS additive and it's fine there too. But as least it's in there for those who need the LS additive.

 

[HOG]

Originally Posted By: MrHorspwer
There is no front differential. The transfer case (more appropriately described as a power take off) is just a helical gear on the transmission output shaft that drives a hypoid gear set. No differential.

For the rear differential, no limited slip additive is needed. The gear lube you're replacing does not interact with the clutches. The clutch is a sealed electromagnetic unit with no provisions for fluid service.

The AC Delco synthetic 75W90 (P/N 88900401) is a very high quality fluid made by Petro-Canada.


Thanks MrHorspwer, I could not find a definitive answer on the front diff, but i guess this is actually the transfer case. Although I trust the AC Delco stuff, I just figured there may be other manufacturers that exceed what the manufacturer offers (such as RP or Amsoil). I'm trying to find some Amsoil Severe Gear, and a store here says they can get it, but its been over a week since I ordered it and it still hasn't come in yet... so I'm not holding my breath. If I can't get that, maybe I'll go with the ACD stuff...

 

[4wd]

+75% of the last 20 years using M1 gear lube - last time M1 and Delvac 1 ... got Redline for transfer case