Here's one I was presented with today. I decided to let a professional Transmission house rebuild my FS5W71B 5 speed transmission. They suggested to fill it with ATF, after the rebuild, being as it is very cold up here in Quebec city, and Martin the owner of the company claims that using ATF in the manual transmission rebuilds he does, is working out much better than standard oil. The issue he claims is with lubrication and the cold, the ATF he says works much better, and his customers are very happy as he has had no returns. He says on cold days, that the GL4, and GL5 is too thick, and the bearings & other parts, starve for lubrication, which is causing bearing failure at an earlier interval. What do you think Tiger Racing? and Datzen Mike, and other Oil specialists? Should I go with the ATF? or stay put with the GL4 - GL5 ? Id' like your input on this...DAttsun Al,
ATF has a viscosity of between 6 and 12 w I think. Automatics have basically the same gears and bearings to lube but they do have an oil cooler. I have 'rinsed out' a 5 speed with ATF before installing it. If you just drive it I guess you can get away with ATF. I don't think I'll use it.
My new '70 Dart 340 4 speed began growling at 6 months and I took it in for warranty work. They changed all the bearings. I took it to my garage and drained the red ATF out and replaced it with 90W GL4. Admittedly I drove the shit out of it with 300 hp. Just sayin'...