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What oil for Datsun 5 speed?

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Bayless

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I have something that states GL-4 75W90 but don't know its source. What I found a the local parts store today was GL-5 synthetic. If the 75W90 is correct, will the synthetic GL-5 be all right? I'm hoping someone who has one will know what to use.
 
No, don't use it as GL-5 synthetic reacts with Bronze parts. I would never use it in an older standard shift transmission, Use what the manufacturer recommends, it's out there.
 
I can only speek from mazda, they recomend the GL4 75W90 and it is stated that if you use GL5 it makes the gears a lot stiffer to select.
 
Thanks mezy. I thought I remembered something about staying with the GL-4 but I can't seem to find it now when I need it (well almost ready). So now I have done a little more research that I should have done before asking. It seems that most GL5 oils contain an additive (sulphur?) that deteriorates the yelllow metal (brass?) in many gearbox synchros. So GL4 it is then even if a little harder to find.
 
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I found something from Royal Purple that was a GL4 and the right weight the last time I did a trans fluid swap in my 5-speed Minor. Think I may have found it at my local parts store.

Redline makes one as well:
> MT-90 75W90 GL-4 Gear Oil <
 
I use Red Line MT-90 75W90 GL-4, per their recommendations. Doug
 
Thanks guys. I got the Royal Purple at Autozone.
 
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