I have a leaky rear differential that I'm gonna be replacing the silicone with a real gasket soon, here in the next couple of days. My question is that my 1997 F150 5.4 liter with the 9.75 Limited Slip rearend calls for 75w140 gear lube. Do you guys run that up here around Fairbanks/Northpole area??? I don't want to blow something out when its 50 below, any info appreciated. Thanks, schmidty

 

I was reading that Amsoil Severe 75w140 synthetic is good for cold weather. If I don't hear anything I guess I'll go with that.

 

I would definately go synthetic. I know the dealership here in Fairanks installs sythetic when they winterize the new vehicles. You may even look to see what the dealerships parts department offers. If you have limited slip, I believe you need to add the friction modifier for it to work correctly.