Nv4500 fluid-
 

Getting ready to do the swap. Need fluid. Obviously the OEM Castrol Syntorc is no longer available. Remaining supply is almost impossible to find and the $$$ is ridiculous. I see several aftermarket brands that are advertised as replacements:

Amsoil-Redline-Royal Purple...

Cost aside, anybody have any knowledge, experience or opinion on one over the other?

Re: Nv4500 fluid-
 

I’m running redline in 3 different trans right now with no issue. Used the AC delco too

Re: Nv4500 fluid-
 

I went straight to the dealership to get mine....but get ready...this stuff ain't cheap...

Re: Nv4500 fluid-
 

amsoil is cheaper than the dealer crap.

Re: Nv4500 fluid-
 

Amsoil Manual Transmission and Transaxle Gear Lube 75W-90. If you sign up as a preferred customer you'll save 25% over retail, earn points towards future orders for additional discounts and get free shipping with orders over $100. I'd be happy to sign you up and be your sponsoring dealer, the cost is $10 for 6 months or $20/year.

Re: Nv4500 fluid-
 

The official oil from GM and Chrysler is Castrol Syntorque with AC Delco or Mopar labels on the bottles.

I've used Torco RTF and Castrol Syntorque in my NV4500's.

Syntorque is a specialty oil for a single transmission... the NV4500... That transmission, in GM dress, ended production almost two decades ago and was mostly only used in 3/4 & 1 ton trucks in the 1990's to any large degree. Castrol can't make thousands and thousands of gallons of the oil to get the price down to Wally World pricing and there are rumors that it is no longer being produced so it will not be going down in price for that reason as well.

One of the important properties of Castrol Syntorque is the slow rate it heats up supposedly because of low friction. It also doesnt attack the oddball composite synchro rings New Venture used in these gearboxes. Torco RTF Gear Oil is a group IV/V oil. It's performance is a very close second to the Castrol Syntorque and it's still being produced. $23/qt from Summit.

The Dodge Cummins boys claim it takes 5-6 full power dyno passes to get Syntorque and 4-5 & sometimes 6 to get the Torco RTF up to 140°F in the NV4500. Most other possible oils fall well short of that and neither oil attacks the synchros.