Has anyone tried swapping out the MT fluid with something like Royal Purple to smooth out the shifting? Any good results or problems with doing that?

 

Yes, I changed mine to Redline and its been good so far. I changed it at around 3K miles. Overall it has been smoother in the cold and especially in warm weather. The main thing I noticed was the 2nd gear occassional grind in the morning dissappeared after I changed to Redline. Its been close to 2 yrs now and its still solid.

 

Does it help with sound? Like the whine etc some of our trannies get

 

How many miles did you get out of yours? I put Redline in mine and the third gear grind hit full force at 28k miles. Having the tranny replaced this Friday.

 

Someone told me not to use anything but the Nissan fluid is a bad idea. Why would that be?

 

Well I only have 11K miles and havent noticed anything weird about the tranny.

As far as the whine goes, that is also one of the things I noticed after changing to Redline. It is not as loud after changing, but it is still there.

I guess only time will tell if something pops up. Im crossing my fingers...

About using just Nissan oil, I dont know its up to you. If you fear the hassle it might pose against your warranty, then I guess you are going have to stick to Nissan's. But im sure the Redline is the same or close to Nissan specs. Im just keeping all the receipts of all the changes ive done just in case warranty issues come up.

I dont really know the real answer to that question...

 

If I use the same rated oil as what is mentioned in the manual, I doubt they can dispute warranty.