After removing the drain plug, the original Dexron III poured out of the transmission. The red color confirms the fluid is the original spec Automatic Transmission Fluid (ATF). The fluid has less than 10,000 miles on it and visually does not look that bad or overheated. Even though the factory service interval is every 12,000 miles, 14 years of age is a long time and it was definitely due for a change.
We are replacing the original Dexron III ATF with 4 quarts of Mopar 75W85 Manual Transmission Lubricant (MTL), Part Number: 04874459, MS-9070.
In 1998, a Technical Service Bulletin (TSB) was issued to address the Neutral-Gear-Rattle “NGR” that happens when the clutch is engaged and the transmission is in neutral. This minor noise is caused by slightly loose tolerances in the transmission’s gears. The solution was to use the thicker Mopar 75W85 MTL (or Castrol Syntorq LT 75W-85W), which helps to cushion the gear movement to reduce the noise.
I find it surprising that anyone who would buy an 8-liter, 10-cylinder monster would complain about a little noise like this, but I digress. The new MTL is said to cause some increased shifting effort at 20*F and below, until the transmission is warm. Since our Viper will never see sub-freezing weather, and since the thicker fluid is reported to make shifting smoother in normal weather conditions and at operating temp, we decided to use the Mopar MTL 75W85.
Trans Fluid Notes By Year:
Earlier 1992-1993 Vipers were filled with Dexron IIe, which was superseded by Dexron III in 1998 and then by Mopar ATF+4 in 2008. The 1998 TSB clearly stated that these cars should NOT use the Mopar MTL.
1994-1998 Vipers were filled with Dexron III (superseded by ATF+4) and are able to use Mopar MTL 75W85 to address “NGR” issues.
Vipers built after 1998 were filled from the factory with Mopar MTL or Castrol Syntorq LT 75W-85W (Part Number 04637579, or GM #12346190). This fluid continued to be used in the Gen-3 Vipers while the 2008+ cars switched back to Mopar ATF+4.
Castrol Syntorq LT 75W-85W has (2) “w”s and is NOT the same as Castrol’s “Syntech”.
NEVER USE GL-5 transmission fluids in the Viper T-56 due to the aggressive additives that will corrode yellow metals (brass, bronze, copper = synchros) in your transmission.
The Mopar MTL 75W85 is clear in color and is easy to differentiate it from the red ATF we are replacing.
After filling the transmission, we reinstalled the lower transmission cover plate.
Quick Reference:
Page 1 – Trans Chassis Plate Removal
Page 2 – Trans Fluid Drain & Fill
Page 3 – Diff Fluid Drain
Page 4 – Diff Fluid Fill, Coolant Drain
Page 5 – Coolant Fill, Brake Fluid, Front Brake Bleed
Page 6 – Rear Brake Bleed, Power Steering Flush
Page 7 – Power Steering Fluid & Engine Oil
6 comments
Have any idea why ATF was specced for a manual? That seems pretty ridiculous to me.
Because the transmission was design to use ATF for good shift quality in cold conditions, compatibility with synchronizer friction materials, and minimized parasitic drag to maximize power to the wheels.
They probably didn’t want to develop a specific MT fluid since most of their vehicles are AT. It just seems a bit lazy to me, especially with a high horsepower halo car like the Viper.
I have no idea what the viscosity is on the Mopar MTL, but I bet it’s higher than Dexron III:
“Manual transmission fluid, as noted earlier, tends to be a higher viscosity than automatic transmission fluid. This helps the fluid develop a thick, durable protective film.”
What about clutch fluid?
The same Castrol SRF as the brakes.
The passion and dedication you have for this project shine through your writing, and it’s contagious. I can’t wait to see what’s next in store for Project Viper. Keep up the fantastic work, and thank you for sharing your journey with us!