I switched to Redline MT-90 at about 4K miles, hoping that it would smooth out the notchy shifting of my 6-speed box, especially into 2nd gear. I noticed a very marginal improvment with the Redline, but nearly as much as I had expected. 16K miles later, and still unhappy with the shifting feel, I bought some Royal Purple MaxGear 75W90 oil (following apexi350z's recommendation). When I picked the car up yesterday after having a dealer install the oil, I immediately felt a difference. The box feels smoother, especially when cold. It's not a huge difference, but definitely noticeable to anyone who is familiar with the particular car and it's quirks. The stick feels 'lighter' in general, so 5th/6th gears require less effort to engage as well. I enjoy driving the car more, since I no longer feel like I'm hurting it every time I shift into 2nd. If you've tried Redline, Amsoil, etc, and are still unhappy with the notchiness of the transmission, you may want to give Royal Purple a try.
Mika

 

Thats great!
Did you have the dealership do a powerflush (they hook it up to a machine that flushes the fluids- more expensive) or just a regular change (which is like changing the engine oil- no machine- just drain and refill)?

Thanks

 

Based on my experience with Valencia Nissan, changing trans oil to non Nissan OEM will void your trans warranty.

 

If Nissan required use of their fluid, they would have to furnish it free. Since I don't believe they are doing that, any fluid that meets the API service rating would comply with the terms of their warranty.

Personally, I'm using Amsoil Series 2000 75W-90. It works for both the rear diff and MT and got rid of the notchiness immediately.

 

FYI: Royal Purple carried at Pep Boys now.

 

Yeah~ I have a new Z with less than 3000 miles and I hate the notchy feel!