Okay guys, I haven't been around here much, but I have come across an issue that I know you BITOG experts can help me with...
I have an Oshkosh M977 HEMTT military 8x8 cargo truck. It has a Detroit Diesel 8V92TA engine, and an Allison HT 750 CRD 5 speed automatic transmission. I recently put this transmission in, and was under the impression that it was a fresh depot-level rebuild. I filled it with Dexron 3 atf (Chevron) and drove the truck for about 400 miles over the last few months. I began noticing the transmission slipping in 1st gear very early on. It has now gotten so bad the truck is barely operable, and the fluid is very dark. I have set up an appointment to have the transmission rebuilt at a factory Allison Remanufacturer next month.
My problem is the Allison rps are saying that any fluid that is C-4 approved is okay to run in it. The factory Allison literature bears this out. The military literature specifies that I should only run 15-40 oil in it. I have spoken to several MILITARY techs who state that they ONLY run 15-40 in their hemtt transmissions, and that atf is not able to cope with the high temps that this transmission creates.
I just want to make sure I am filling this tranny with the right stuff. Is 15-40 C-4 certified? What brand is best? I usually run Delo 100 or 400 straight 40 weight in the engine.
I have an Oshkosh M977 HEMTT military 8x8 cargo truck. It has a Detroit Diesel 8V92TA engine, and an Allison HT 750 CRD 5 speed automatic transmission. I recently put this transmission in, and was under the impression that it was a fresh depot-level rebuild. I filled it with Dexron 3 atf (Chevron) and drove the truck for about 400 miles over the last few months. I began noticing the transmission slipping in 1st gear very early on. It has now gotten so bad the truck is barely operable, and the fluid is very dark. I have set up an appointment to have the transmission rebuilt at a factory Allison Remanufacturer next month.
My problem is the Allison rps are saying that any fluid that is C-4 approved is okay to run in it. The factory Allison literature bears this out. The military literature specifies that I should only run 15-40 oil in it. I have spoken to several MILITARY techs who state that they ONLY run 15-40 in their hemtt transmissions, and that atf is not able to cope with the high temps that this transmission creates.
I just want to make sure I am filling this tranny with the right stuff. Is 15-40 C-4 certified? What brand is best? I usually run Delo 100 or 400 straight 40 weight in the engine.