#59368

Tom,
Have you ever used (observed) 80wt motorcycle (2-stroke, off-road) transmission “gear” oil. It’s viscosity is just like 30wt engine oil, but has better gear face protection, plus it’s designed to work with clutch friction plates, so it’s very compatible with the overdrives. Engine oils & “gear” oils have different rating scales. Maybe you have the rear axle oil (hypoid gear oil) on your mind. I have found many trannys where the previous owner used hypoid oil, even in overdrives.
Tom, look at this chart that I lifted off the web page:
http://www.repairfaq.org/filipg/AUTO/F_oil_facts.html
___________________________________________________________
| |
| SAE Gear Viscosity Number |
| ________________________________________________________ |
| |75W |80W |85W| 90 | 140 | |
| |____|_____|___|______________|________________________| |
| |
| SAE Crank Case Viscosity Number |
| ____________________________ |
| |10| 20 | 30 | 40 | 50 | |
| |__|_____|____|_____|______| |
______________________________________________________________
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42
viscosity cSt @ 100 degrees C

(maybe just go there), as you can see SAE has set up two different ranges for gear & crankcase viscosity numbers. I hope this helps clearify what I was recommending.
Jan