I use Sta-Lube GL-4 gear lube,in the transmission of my 37 Ford I use the SAE 85W/90, in the Columbia rear I use the straight 140W both I bought from NAPA,both say on the back Not corrosive to copper,bronze or other non ferrous metals to me those are yellow metals,not white as mentioned in another post.I have always believed that GL-4 was the one to use and not GL-5 but someone else has posted not to even use GL-4,but it has worked for me and after one change I sure did not see anything but gear lube I could have/should have put back in with no metal particles. CRC makes Sta-Lube, the part # for 85W/90 is SL24239 and for the 140W is SL24238. The 140W in transmission makes it little harder to shift when its a little cold out,but I prefer it in the Columbia all year as at least it stays in banjo better than the 85/90.