Gear oil question
 

What type of gear oil do you use in your trans and rearend. The owners manual says 90W for rearend(GXL) and 80w-90(or something like that) for the trans. Do I use what the manual says.

thank you
derek

I'm using Red Line's 75-90 synthetic in the trans. Some guys like Red Line's MTL (Manual Trans Lube) instead. I don't know if there's much difference between the two. It made shifting on cold days much easier, and 2nd gear doesn't crunch anymore. Expensive, at $9/quart, but worth it, IMO. I still have regular gear oil in the rear.

Yes, use what the manual says. You might want to go to a synthetic, such as redline, NEO, etc.... Synthetic oils are considerably more expensive than regular oil though, but can be worth it if you are experiencing any minor wear issues.

Royal Purple Max-Gear in the tranny and diff for my '87/GXL. It's 75W90, but works for our cars.

i was gonna use that purple stuff, but it's hella expensive and i decided to just abuse the shit outa my tranny and rebuild it early next year...:p:

Well, "Go-For-It" if you have that kind of money to waste :) Preventative maintenance is my preference, plus being a woman, I don't know jack about rebuilding, LOL.

80W90/85W90 is a little thick for the tranny. You need 75W90 for the tranny. If you go with Redline, the product you want is MT-90. Anybody elses product, use there 75W90 weight.

I have been using Redlines Super Lightweight Shock proof in all my cars and trucks rear ends and have been very very happy with it.

The super light SP is the equivelent of 75W90.

As far as the tranny, I normally use Redline MT-90, but if I find a tranny that is in bad shape, I'd recommend the super lightweight SP for that as well.

Actually Mazda does suggest straight 90W in all temps above 0F, and 85W90 if temps are below 0F

Redlines Super Lightweight Shock proof believer +/-, using it on the tranny as we speak :)

I would advise against royal purple.. I remember reading an artice about where it was tested, and proven to deteriorate brass.. Guess what your synchros are made out of?

yeah, but almost all gear oil will start to eat brass at temps above 200F (although redline claims theirs does not).

I know Mazda recommends strait 90W for summer temps, but that recommendation makes for a very slow shifting tranny. Agree?

I couldn't say. I only use synthetic Redline (like the MT-90 or SLSP both of which are really a 90W or 85W90 depending on your point of veiw) in the gear boxes and find shifting much better than average.

But I can say that, I would not ever be using a 75W90 or 75W140 in a RX-7 gear box, be it synthetic or conventional. There would not be enough shear strength to prevent gear wear. While shifting might be improved, power handling and longevity would be radically decreased IMO.

My question is....why does it stink so bad?
Man! That stuff is rank! You can actually taste it! Yuk!

Interesting opinion. But isn't the Redline Super-Lightweight Shock Proof rated as a 70W90 equivalent? I would think the Lightweight product (75W140) or MT-90 (75W90) would be a better match for our requirements.