Sorry if this thread has already been made, I had a little trouble finding it if it was. I was doing a little research as to what oils I should use in my tranny and rear diff. My car has about 72000 on it and I had a new motor put in but I havent changed my gear oil or my differential oil since I got the car and the Manual says 60k for the reccomended change. I know some people put synthetics in their trannys and diffs (they didnt have rx8s) so I didnt know what people reccomended. I went on a few sites and I was just wondering if any of you had reccomendations.

http://www.5cats.org/rx8/trans_diff_refill/

http://www.rx8web.com/forum/showthread.php?t=4946

Any help would be great. I really appreciate it.

*shurgs*

There was a thread about tranny/diff oil just like last week

I be nice today

For Tranny, You can use anything thats GL-4 rated @ 75w90

Keep in mind there are a few products on the market that they "claim" it works for both GL4 and GL5. Do NOT use those products for our Transmission. For Example, Royal Purple and Pennzoil. They both have a product that they said works for both GL-4 and GL-5. Dont use it. Use a TRUE GL-4 rating Gear oil for our tranny like Redline's MT-90, Amsoil's Synthetic Manual Transmission and Transaxle Gear Lube, etc.

For Rear Diff, Anything GL-5 rated @ 75w90 (Some people use 75w140 cuz it offers a lot more protection with about 1-2% performance hit)

Transmission: Redline MT90

Differential: Redline 75W90

Transmission: Redline MT90

Differential: Redline 75W90

Agreed

does it matter whether I use synthetic or not?

For gear oil, the cost is about the same (synthetic mightl cost a few bux more, but usually about the same)

so why not Synthetic ? You just need like 2 for tranny and 2 for rear. not that expensive.

and if there is a pepboys around your area, you can get them cheap. Search for my thread :)

ok thanks guys i really appreciate it.

if its only a few bucks more I might as well but do you think it will make a huge difference??

Does anyone know what Mazda uses from the factory and at the dealers for the transmission oil? I'm experiencing the 09 5th and 6th gear grinding. The car is going in tomorrow, but I'm wondering if I might help the situation by using Redline MT-90. On the miata.net forums, there is also a large thread about a Motorcraft synthetic GL-4 transmission oil that's supposed to be very good (and is apparently twice the price of Redline MT-90).

Does anyone know what Mazda uses from the factory and at the dealers for the transmission oil? I'm experiencing the 09 5th and 6th gear grinding. The car is going in tomorrow, but I'm wondering if I might help the situation by using Redline MT-90. On the miata.net forums, there is also a large thread about a Motorcraft synthetic GL-4 transmission oil that's supposed to be very good (and is apparently twice the price of Redline MT-90).

Your tranny has a problem.

Nothing to do with oil.

Trans (http://www.amsoil.com/storefront/mtf.aspx)

http://www.amsoil.com/StoreFront/images/mtf_qt_300.jpg

Diff (http://www.amsoil.com/storefront/svt.aspx)

http://www.amsoil.com/StoreFront/images/svt_qt_300pxh.jpg