Hey y'all,

So I converted my automatic in my 99 ram 1500 to a NV4500HD years ago, smartest mod I ever did to this truck. I've finally got the engine running again and I was considering changing the fluid. It was about 10 years ago and maybe 20,000 miles ago at most that I put in the rebuilt NV4500 HD transmission in, and the truck has sat for a good 4 of those years. I filled it with 5 quarts of the mopar factory fluid for it (I forget the exact name now but its the specific one called for OEM) when I installed it 10 years ago. I've checked the fill plug a few times since then and it has fluid still at the right height.

Anyhow, what do you guys think, should I swap the fluid? I've been considering it. Especially because I was watching an episode of Leno's Garage and he and his guest spoke very highly of something called "Redline MTL" they said that in their BMW stick shifts that it really perked up their shifts and made it feel almost like new synchros.Jay Leno does like to talk up products, but he's usually not talking out of his *** so it made me curious. My shifts are fine but they could be better I think. I did some cursory google searches which showed that the NV4500 HD is compatible with this stuff. What do you gentlemen think?

Here's a link to the episode it's the one with the BMW 325i Touring .

 

Andrew at Long Range Gear says the only fluid that can be used for him to honor his warranty is Redline MT85. So, MT85 is probably not a bad choice.

 

I have no experience with MT85, but after all that time, yes, you probably should just change it. It’s probably fine, but new fluid is cheap insurance.

I do have experience with Royal Purple SynchroMax MTF in my Liberty with an NSG370 transmission. It was pretty crunchy going into 1st, 2nd, and 3rd gears on the fluid I got it with. The RP made a pretty big difference. 1st was still crunchy sometimes, but 2nd and 3rd were great. 100k miles later (253k mi on the jeep) and everything is still good. I changed fluid 20k miles ago, and it still came out noticeably purple.

If MT85 is on par or better than the Royal Purple, I would definitely suggest the fluid change.


EDIT: I just looked up MT85 and saw it is a heavy gear oil. Royal Purple SynchroMax is a much thinner fluid, so don’t anybody take this as a recommendation for this specific transmission.

 

For whatever reason the NV4500 was allegedly VERY picky about fluid and initially Chrysler was very specific you had to use their fluid only, which I believe later became available as Castrol Syntorq. Supposedly the GM and Mopar fluid today is still made by Castrol.

But now we at least have other aftermarket alternatives like Amsoil and Redline.

I do not believe the NV3500 or 5600 were this restrictive on fluid, but verify before listening to me.