What fluid to run in my Getrag/Tcase/Diffs/Cummins? Opinions?

[Niki]

I know it says 5W30 in the FAQ for the trans, but can I run 10W30 or 10W40 in the summer? My Getrag has a little seepage but nothing major, and 165K on it, should I switch to synthetic or stay w/ reg? What about the Tcase? I have a bunch of 80W90 Amsoil, would this be OK in the diffs, even in the winter? What about the motor? Switch at 165K to synthetic? Which one, Rotella synthetic or other? I've always ran Delo or Rotella in my other Cummins' and never have had a problem, but always open to new ideas/extra mpg/quicker warm up!

 

[dpuckett]

Personally, I have run 15w50 in the transmission in summer when towing. Synthetic or dino is up to you- I think the important thing is to get it that 1-1. 5qt over stock fill. Since you have some seepage, it coule become a leak if you went to synthetic. The main thing is engine oil- the lighter-than-gear-oil weight.



10w30, 10w40, 15w40, et al, shouldnt hurt it a bit.



Daniel