Once again, the age-old quandary of what lube to put in the G56 6-speed manual trans in the Dodge Ram diesel.
I have been running AMSoil ATF, which is what they recommend for the application. Chrysler recommends their C+4 ATF fluid. In my opinion, Chrysler really screwed the pooch by recommending ATF in the G56, when in medium duty European trucks, Mobil Trans SHC 50 DC was recommended. There was a wide gulf of viscosity between the Mobil fluid, at 15.7 cSt, and the Chrysler C+4, which was 7.5 cSt. I have read a lot of stuff on the Interweb including some lengthy and colorful threads on BITOG that showed up in Google searches. There never is a resolved outcome of any of the discussions.
Mobil Trans SHC DC is no longer available. Nor is Mobil Trans SHC. Some equivalents from other oil companies are available that claim to be replica fluids (of the SHC, not the DC version). But they're expensive.
Now we're heading into hot weather, and it's time for a fluid change. I want something with higher viscosity, but if I want to respect the Chrysler recommendation, I could find a higher viscosity ATF.
I looked on Redline's site, and they have the High Temp ATF, at 9.5 cSt. 27% higher viscosity is a significant step up from C+4. I e-mailed a question on the Contact page, and got a reply from Dave at Redline. He recommended either the MTL or MT85. MTL is 10.4 cSt. MT85 is 12.0 cSt. I have experience with MT85 on my old truck. It gave the best shifting feel of any fluid I ever ran in the NV4500.
And then there is AMSoil MTG, which I ran in the old Dodge because of the higher viscosity. It was 14.0 cSt.
So there are fluids I have mentioned above ranging in viscosity from 9.5 to 14.0 cSt. Which would you pick?