Hello all, first time post, and I've read a few posts on transfer oil. My question is a bit more basic. Do you all recommend the same transfer case oil as your diff oil? I just changed my diff oil using 85w-140 (have aftermarket eaton lockers and this was recommend by the mechanic), and I'm having trouble getting hold of my mechanic on transfer oil recommendations. Any suggestions or advice is welcome. Thank you!
Question on Recommend Transfer Case Oil
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I use Valvoline Flexfill SAE 75W-90 Full Synthetic in both diffs and the transfer case. I find 85w-140 too heavy, not great for cold weather, and you will take a MPG hit...
More Information: FAQ - 80-series FAQ for General Info, Modification and Repairs - https://forum.ih8mud.com/threads/80-series-faq-for-general-info-modification-and-repairs.84888/
More Information: FAQ - 80-series FAQ for General Info, Modification and Repairs - https://forum.ih8mud.com/threads/80-series-faq-for-general-info-modification-and-repairs.84888/
Same 80-90
140 is out side of OEM spec
140 is out side of OEM spec
hisandhers80s
SILVER Star
I use the red line 75w-90 in both.
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- #5
Thanks all. Odd that my mechanic recommended that…Is it something to do with the aftermarket lockers? Relatively new to working on cars but enjoying the ride.
Get a new mechanic.
Better yet start doing your own work.
You can go to Eaton website to see what they recommend, but I still say 90w
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- #7
Looks like both google and Eaton recommend 80W-90…stupid of me not to verify. Seems like I get to drain the diffs this weekend too…Thank you
He's lazy. Wants to fill both with the same product because it's easier
FWIW, I've been using 75W90 in all 3 diffs for the last 30 years.
I stock 1 grease for everything (Amsoil moly) and 1 gear oil (Amsoil 75W90).
I stock 1 grease for everything (Amsoil moly) and 1 gear oil (Amsoil 75W90).
I run 75w-140 synthetic in all 3, but that's because I fairly often find myself in the situation of 2nd gear, pedal on the floor at 4,000 rpm, for 20 minutes straight, towing a trailer up mountain grades.
75w-140 typically has the same viscosity as 75w-90 at a 40F higher operating temperature, within normal 100-200F operating temps. I hope I'm not higher than that...
I don't actually know my temps, but I can only assume running peak power for extended durations makes for a lot more heat than standard cruising or towing on flat ground. There's no coolers on those 3 other than the air against the case and housings, and there's not as much of that in the 45-55 mph range compared to how much power is being transmitted when climbing grades with a trailer.
If you don't find yourself at peak power for extended durations, I wouldn't use anything that has 140 at the end of it. You're just wasting gas and making it even slower.
75w-140 typically has the same viscosity as 75w-90 at a 40F higher operating temperature, within normal 100-200F operating temps. I hope I'm not higher than that...
I don't actually know my temps, but I can only assume running peak power for extended durations makes for a lot more heat than standard cruising or towing on flat ground. There's no coolers on those 3 other than the air against the case and housings, and there's not as much of that in the 45-55 mph range compared to how much power is being transmitted when climbing grades with a trailer.
If you don't find yourself at peak power for extended durations, I wouldn't use anything that has 140 at the end of it. You're just wasting gas and making it even slower.
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- #12
Thanks, all. Went with 80w-90 Lucas in the t case and diffs. I’m not towing anything, just camping/off-roading with a RTT on the top. Seems like the best option.