GM 12378261 75W-90

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Oct 3, 2008
I need to service the rear axle on my Grand Marquis, and I've had zero luck with anything 75W, let alone 75W-90. The only one I've found was ACDelco Supreme Plus 75W-90, sourced from Delphi Belgium, but that was also out of stock. The GMC dealer instead had Genuine GM 75W-90 synthetic GL-5 available, which I just purchased for ~$16 a liter (I need 2L). It's got a nice scent to it, too...smells like grapes. Just wondering what base stock this comprises of though, anybody know? I think it's safe to assume Group III? Also, who's GM's supplier? It seems Fuchs is their supplier in Australia for their ACDelco range, but I haven't found anything about their US supplier. Could the Genuine GM stuff be sourced from a different supplier than ACDelco? Thanks!
All 75w90 gear oils are synthetic. They are a group III synthetic unless you go with redline, royal purple, or amsoil which I believe is a group IV. From what i've heard there isn't anything special about the gm grape juice except the price. Just rmember if it calls for friction modifier. They don't have an autozone in kuwait?
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Valvoline sells conventional 75W-90 GL5 if you want it. I buy it at NAPA and use it in my Tundra front diff and transfer case.
Thanks for the input! thumbsup We haven't got an Autozone, but there are other stores locally that sell stuff in a similar fashion. Only problem with those are, they don't really sell much of the premium stuff. People often go to those places for cheaper aftermarket alternatives, and if an aftermarket product is more costly than the dealership, they avoid it all together. Only thing I could find was 80W-90, and I was after synthetic. I haven't got a locker in there just yet, but am upgrading to a 3.73 locker rear end soon. thumbsup
You got a deal on the GM fluid--dealers charge about $30 per quart in the States. When the grape juice first came out, it was made by Texaco. This was the fluid specified for the Eaton Gov-lock rearend in 1999-up pickups. If you are installing a clutch-type limited slip, I think you will also need to add friction modifier. The fluid for Camaros and Corvettes should be a different part number, as they had limited slip. Of course, I could be all wrong about this since I don't have part numbers in front of me, and I don't know if the fluid for cars had the pretty grape smell.
Thanks for the input! thumbsup I replaced the fluid this evening, difference is quite noticeable. The car originally came with 75W-140, and I only realized this tonight when I saw the tag, as I was changing the fluid myself this time. The last time I had a mechanic change it out, and I used Motorcraft Premium Rear Axle Lubricant 80W-90 with 40 ml of MoS2. Anyhow, the car feels noticeably lighter, and acceleration after a downshift to 2nd or 3rd is much more fun! Wonder if fuel economy will be affected.
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