For those of you using Redline, I'm planning to do MTL/MT90 mix. Are you guys using this same mixture for both the differential and the tranny?

 

NO. You should use a 75W-90 GL-5 fluid in the differential. MT-90 is intended strictly for use in manual transmissions.
If you want to stick with Redline, you should use their 75w90 High Performance Gear Oil.

 

OK, so MTL/MT90 mix for the tranny, and 75W90 Gear Oil for the diff?

 

Yes.
There are other products out there, though.
Right now, I'm running Specialty Formulations MTL-P in the transmission, and Specialty Formulations 75w90 gear oil in the differential. I like both.
MTL-P is the only fully-synthetic 75w85-weight manual transmission oil I know of (besides Castrol Syntorq LT, which is designed only for the NV4500 truck transmission)
75w85 is the weight originally specified by Nissan (though I think they now specify 75w85 or 75w90 GL-4)

See: http://specialtyformulations.com/MTL-P.htm

Mika

 

I just got RedLine MT90 fluid in my Z. Works great warm.

But it sure is not for cold climate! Below freezing, some gear are hum... closed... And the trany whine is very loud...

 

I spoke with a few mechanics and they all said that Royal Purple is garbage, I am about to replace my trans-fluid and have been researching heavily. I think I am going to go with AMSOIL or RedLine, though I am still trying to track down the proper weight. I read AMSOIL 75W-90 will suffice but I am not positive.

 

I changed my trans and diff fluids friday. Have an 05 35th ann edition with 6 speed about 83k on it. I just got the car a few months ago noticed it was hard to shift when cold and when it got very out hot (summer). I did my research and seems like everyone has had either good or bad experiences with the different types of oils used...
I decided to use the royal purple in both trans and diff, royal purple states its safe for gl4/5. The min I changed the fluid and drove the car it felt like a brand new car. It shifted very smooth no grinding no weird noises and the hum I heard at about 80mph on the interstate went away. I put about 100 miles on it just to make sure and wanted to see how it felt on a cold morning. No change still feels like new. Hopefully the oil is not going to do any damage in the long run. Just wanted to throw my experience out there.