Anyone know which Royal Purple to use in NV5600 six speed?

 

im gonna give you my honest opinion...i ran it in m 5600 and after 3-4k miles the fluid broke down and the shifting was crappy. it would grind, was notchy and made noise. I drained it and it wasn't purple anymore, it came out brown. the best fluid I have tried thus far has been redline MTL.

 

I have the RP SynchroMax in mine. Check out their website.
It's been almost three years now, and about 40k miles. Still nice and smooth....when it's warm. Cold I notice some notchyness to it. I think I may try the Redline when I hit 50k....just because so many people say good stuff about it.

 

I have used Redline MTL in my NV5600 and thought it was better than the fluid that comes in the trans although I have read it runs at a higher temperature than the standard fluid. I believe the increased temps have burnt out the seal between my trans and transfer case making it leak. I have also been talking to an off road racing gearbox builder and they claim Redline Heavy Shockproof gear oil is the absolute best gear oil they have ever seen. I have been topping my trans off with this fluid as it leaks daily and have noticed smoother shifting, much like it shifted when the trans only had 45,000 miles on it. I will make the complete change to the Heavy Shockproof oil when I get around to changing the seal. Eric

 

I noticed no difference at all going from factory oil to Redline MTL, 5 1/2 quarts. and the oil I drained out looked perfect, some brass reflected in the light, but the oil was clear amber. $50 I could have saved.

 

I run the Redline MTL at 6 qts. I changed out the stock 'lifetime' fluid at around 57K. It was black with a small amount of yellow metal flakes in it...normal. It shifts a lot smoother w/ the redline, but I really don't have anything to compare it to other than dirty stock lube. I also ran the Royal purple gear oil in my diff's, but haven't drained any out as of yet. The rear was black, the front was an opaque yellow and seemed pretty thick. I found this to be normal for the front after posting some questions regarding this. I chose to go that route from researching a few searches regarding trans lubes on this site. So far so good. Good Luck, Kurt