Gear Lube for Front Dana 60 Axle - Which One?
 

Going to be doing a Diff oil change on my front Dana 60 Axle. Ford recommends 80W-90 Synthetic for the front axle. I plan to do a fair amount of drag racing this next year and I'm wondering if running 75W-140 in the front has any drawbacks? I will be running close to 100mph in the 1/4 mile in 4Wheel drive and figured maybe the thicker oil would be better. The gear lube of choice will be Amsoil Severe Gear. Thanks in advance!

I wouldn't, 140 is for extreme loads, I don't see that kind of pressure inflicted on the front during drag racing. I always ran Amsoil 75-90 in the front sled pulling, with zero issues, and that was with hanging weights.
For drag racing, I wouldn't run 140 in the rear, either.

I agree... and actually, Ford's front fill isn't synthetic either.. just the rear.

The front is 80w/90 dino, and the rear is 75w/140 syn. The heavier weight oil would probably hurt you for windage losses.

Good information! Thanks. I do a fair amount of towing with the truck as well so not sure it is wise to drop back on weight for the rear axle? What do you think? But, I will definitely be running 75W-90 Severe Gear in the front now.

Dino Oil in the front diff? But the service interval is still 100,000 from Ford? Am I missing something?

You might want to check that interval.. I'll look at my book tonight, but I'm thinking it was 50k or 75k... not too many people are going to burn out front oil. When I change all my fluids, they'll all be syn.

Drag racing might see the difference in weights for the rear, but I think sled pulling you're not really turning it fast enough that you'd see any appreciable differences. Heavier oil would give you a little better protection over time though. I'll bet it's minimal though.