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**hatzie** · 10-12-2018, 05:51 PM

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.

10-12-2018, 05:51 PM	#6
hatzie Moderator Join Date: Oct 2008 Location: Wentworth, NH Posts: 4,916	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. __________________ 1959 M35A2 LDT465-1D SOLD 1967 Dodge W200 B383, NP420/NP201 SOLD 1969 Dodge Polara 500 B383, A833 SOLD 1972 Ford F250 FE390, NP435/NP205 SOLD 1976 Chevy K20, 6.5L, NV4500/NP208 SOLD 1986 M1008 CUCV SOLD 2000 GMC C2500, TD6.5L, NV4500 2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263 2009 Impala SS LS4 V8 RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials... 1973-1991 GM Light Truck Service, Unit/Overhaul, Wiring Manuals, Parts Books and Some 1968-1999 GM Service Training textbooks in PDF 1988-1998 GMT400 CK service manual project 1988-1993 GMT400 CK parts books. 1967-1972 GM Light, Medium, & Heavy Truck Service Manuals in PDF Please include at least the year and model in your threads. It'll be easier to answer your questions. And please let us know if and how your repairs were successful. Last edited by hatzie; 10-13-2018 at 08:48 AM.