I've heard that rumor myself, but I can't see where that would have better results than what is recommended.



I *have* heard of people running 90-140 in their differentials, but they had to do some kind of seal work, as it (supposedly) tends to ,want to migrate out of the axle shafts and up the driveshaft housing, putting it where you don't want it.



On the other hand, Ruckstells use a different grease (I saw it on someone's websie, I think it's 90w or 90-140, but the gearbox apparently needs the extra fluidity).



Me, I use 600W... I used to get it from a local old car parts place (Mal's A sales in Martinez, CA) but last time I checked I couldn't find them... maybe out of business??) I would assume any of the big vendors would have it (I hope I can find some anyway!!!). I've heard you can get it through industrial supply places and lube jobbers (esp. if you're in "farm country&quot but I don't know for sure.