I have a slight bearing noise in my rear diff. Not too bad, can be heard with the back glass opened. I assume it's the pinion bearing. Is a 9.25 corporate axle, 155k miles. Now I have a junkyard axle waiting if I need it, but in the meantime I was going to change the fluid in there for a different type and see if that would make any difference. I realize it probably won't, but I'd like to look around inside the pumpkin anyway. Manual says 75w90, but I was thinking about trying 75w140. The 75w140 would be thicker, right? Which I guess could reduce noise... What do you guys think? I already know it probably won't help much if at all, but I know sawdust will make it quiet (for a while), so I thought the thicker oil might too. Isn't the 75w140 a thicker weight oil when hot? Or have I got all the designations confused?

 

www.bestlubeusa.com/gearlube.pdf Heres a read for all the ppl asking about gear oil might put it in with the gear FAQ post?

 

the 74w140 is just for cold weather....80w90 will do just fine....

 

75w140 is recommended if you tow a lot, it is thicker.
80w90 is fine if you don't tow a lot.

Noise a pinion bearing with a couple chunks missing from some of the rollers makes.
http://www.youtube.com/watch?v=wq2GAGBzU4s
http://www.youtube.com/watch?v=WTXlqa8pX90