gearbox oil 75W85 GL4 or GL5?

[carlv12]

Hello,

I have a 2004 Viper SRT10 with stock Tremec T56, but with a lot of other modifications like Paxton etc..

Dodge is now here in Spain represented by Fiat and I asked them about the transmission oil and they told me ATF4. But my owner's manual says that I should use a synthetic 75W-85 oil.

I have searched a lot in the web and a lot of cars fitted with the Tremec T56 were filled up with ATF4, but NOT the Viper due to its huge torque. I my particular case even more torque due to the Paxton supercharger.

Some say only use API GL-4 oils in a transmission. GL-5 oils are for differentials and have much different chemistry. Some oils claim both GL-4 and GL-5, but don't use a GL-5 only oil.

I can buy this synthetic 75W-85 oil here in Europe, but should I use GL4 or GL5???

I hope you can just clarify this and help me

Thank you and best regards from sunny Valencia

Carlos

 

[Steve-Indy]

Hello, Carlos...hope all is well with you.

Our sources here say that ATF+4 is now the lubricant of choice (as supplied by CJDR via dealership parts departments) for Viper T-56 cars (99-06)that originally came with Mopar Synthetic Manual Transmission Lubricant 75W-85...which is, as you know, rebranded Castrol Syntorq.

While I have not yet switched our Vipers from those years over to the ATF+4...I will be doing so in the future.

 

[carlv12]

Hello again,

ATF+4 is thinner than the 75W-85 = therefore Tremec filled their T56 gearbox with ATF, but NOT for the Viper's. This engine has much more torque and it is NOT limited electronically like on DSG or other modern gearboxes. On cars with a supercharger or Turbo even more, so it could make sense to use the 75W-85 oil even as GL5 that has a higher compression resistance. What do the Paxton and TwinTurbo guys use?
The main problem with GL5 is that is designed for hypoid gears that are in rear ends, NOT manual gearboxes and that the additives could damage the synchronisation. So I guess synthetic 75W-85 GL4 will be the best.

Thank you

Carlos

 

[Steve-Indy]

ATF+4 IS the factory transmission fill for Gen IV and Gen V Vipers. It works quite well for street use.

 

[lefty232]

We use ATF4 in the comp coupe race cars, never had an issue with over heating or losing a tranny.

 

[Catwoman]

Hello Carlos.
I´m using Motul Multi ATF in booth my Vipers Gen III and V. Gear shifting goes much easier with ATF than with 75W - 85. I´m often out on Track days and havent had any problem since I shifted Motuls products.