GM Specification 9986115 equivalent - again

[Hank30721]

OK...I've searched and searched and am more confused than ever. Is there an equivalent out there?

I bought (last fall) a 2001 K2500 Suburban w/the 8.1l V8 and the locking diff rear. It now has 110,000 miles on it. Since I tow a fair amount with it I was going to change the rear diff fluid before a long trip next month. The previous owner had the rear serviced at the dealership using the expensive grape juice at 92k miles.

I called the dealer asking for the cost of the diff fluid (old part #12378261, new part #89021677) and it's $35/quart(!) Is there a consensus on an equivalent?

 

[fixit301]

I used Royal Purple in my 07 Silverado diffy. Also I believe Amsoil meets the spec. No problems with the Royal Purple gear oil.

 

[pickled]

Amsoil Severe Gear 75W90 or 75W110 are your friends...it doesn't smell pretty like the grape juice, but your wallet won't care about that! The last 6 GM differentials that I did did not require any additional friction modifiers either....just poured in the SVG went and did a few figure 8's and everyone has been happy ever since. Be sure not to ignore the front diff as well (if you are a 4x4) because the wear metals that accumulate in that thing are unreal!

 

[daman]

Any oil will work just fine,you don't need the GM stuff i use
M1's 75w90 in my '99,check your owners manual to see if you need
a diff additive.

 

[JohnBrowning]

First when GM did away witht he dain plugs in a lot of their light duty axles they went to synthetic in the rear. Then they started haveing some issues with vechiles in cold climates so they went back and decided that all trucks should have synthetic int he rear axle assemblythat are going to a cold climate. Latter they realised that they could revise their fluid change interval and decided to elimanate it all together for their axles and called their synthetic fill "filled for life"! This reduced their cost of ownership and such for commercial accounts. Over the years GM has used a variety of dino and synthetic fluids most of wich have come from either Texaco or Mobil. So any synthetic gear lube will work just fine. I would stick with M1,Amsoil,Redline,Dello,Schaffers CenPeco etc.....

 

[PT1]

Get it on ebay for about $11/qt shipped. I stocked up 6qts for $79 total.

 

[daman]

All GM trucks come with syn.now,my '99 came with syn.,to the
OP i'd stick with a good synthetic.

 

[NHHEMI]

The price of the "Grape Juice" is ridiculous. All that stuff is, is synthetic 75W-90 with some friciton modifier. Any of the quality aftermarket synthetic gear lubes w/ FM will work.

RP's MaxGear works great in place of it for $9 a qt. Used MaxGear 75W-90 in the 07 NBS Silverado's rear axle without a hitch. If anything the LS(G80) worked smoother when it engaged and disengaged than with the factory fluid. I will use MaxGear 75W-90 in the new SUV to replace the GJ as well. I can buy the RPMG 75W-90 and have it swapped for almost the same cost as JUST buying the GM fluid.

 

[turbhoe]

why would my front end call for stuff with friction modifier? i have the "f4wd" AWD and it calls for 12378261 where as the s4wd (selectable) requires 1052271 or sae 80w-90 gl5

 

[Rhymingmechanic]

Hank30721,

Amsoil Severe Gear 75W-90 is working fine in my 2001 Silverado half-ton that calls for the mysterious 9986115. It doesn't seem like your current fluid would be worn out in 18000 miles, though. Does the Suburban manual spec a really short interval for towing? The change is easy enough with a drain plug, but maybe the effort and expense could be put off until after the trip. Of course, that depends on whether you're towing a bulldozer or a bass boat.

 

[wapacz]

I wonder if the gm stuff is an ester base. Since esters can have a fruity smell some times.

 

[Rhymingmechanic]

Not sure about the composition, but it seems like I've seen the GM stuff called grape "scented." It smells like grape candy or kool aid. Maybe the smell is added so techs can distinguish oil types?

There's a line of fuel additives that make your exhaust smell like vanilla, orange, or whatever. If that stuff is compatible with oils, maybe it could catch on around here to add a new layer of enjoyment to the oil experience.

 

[Falcon_LS]

To be honest, I just went with Mopar 75W-140 full synthetic in the Avalanche. The GM stuff was just too pricey, and I couldn't find an alternative synthetic of the same viscosity. I change it out every 25,000 miles anyway, and this vehicle does tow quite a bit in high temperatures, so I just went with it.