eltonjohan said:
I'm about changing the oil in my stock 4 speed manual gearbox, but am a bit confused about what oil to choose.
In the manual "SAE 80" oil is recommended but also says that it shouldn't be of hypoid type. The oil I found so far is a "SAE 80" but is also specified to be used as a hypoid oil... I would be happy if anyone has a recommendation of what oil to use! Regards Johan
Use Hypoid lube at your own peril on a stock manual transmission. It is not recommended for a reason.
Hypoid additives are incompatible with the phosphor-bronze /brass synchros in your manual transmission. Evidently, the strong sulfur-smelling additives have a corrosive effect on bronze-brass and similarly based metals. Hypoid gear lube is more typically used in hypoid/bevel cut gears found in differentials and manual steering boxes. THe hypoid additives lend the lubricant greater shear strength which is important for bevel cut gears. There were other transmissions that could use hypoid gear oil, but
not the manual transmissions BMW used in the 60's and 70's. I think there were Japanese made manual transmissions that also had phosphor bronze synchros too, so you might want to explore where those Datsun owners get their lubricants. Many European makers of the era used the same transmissions, but there may be exceptions.
One indicator is a GL4 on the label (for non-hypoid) rather than GL5 or GL6 (for hypoid). It is available, you just have to look a little harder for it. If you read your manual, you will notice there is an "emergency" alternative: ("Hd engine oil).
http://www.cscoupe.org/tech/handbook/at_a_glance.htm Another possibility is automatic transmission fluid. I would not be surprised if you found synthetic gear oil compatible with all transmissions - without potentially corrosive hypoid additives. The synthetic lubricants may not need the hypoid additives because of its superior anti wear properties. Look on the various oil manufacturer's web sites. Just read the labeling carefully, or be very lucky. If all else fails, there is always the dealer.
Good luck