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Exactly right ! Sometimes it's just the sludge holding things together. Then along comes clean fresh fluid and washes all the gooey sludge away.

There are several combinations of transmissions you can order from Allison. Many ordered a "drop box" which is a reduction unit with front and rear outputs optional. Basically a built in transfer case. They use Helical gear to gears in them so they need the "heavier" weight oils in them. They...

I never said the military was the only ones who could use engine oil. I know Allison OK'ed the use of "Special" C-4 rated oils in "off-road" transmissions, those that used Helical gear to gear drives in them. The also allowed the use of C-4 oils in "Desert" conditions under extreme...

Thank you "glcaines" for this excellent information. We as a community need to spread accurate information about our vehicles if we are to continue as the "main" source of military vehicle knowledge. Also your practical information about converting your AT1545 back to the proper fluid and how it...

Floridianson look where they allow this use though. Here's the page from the MT600 series you posted about. You see their use in "drop boxes" which have helical gear to gear contact.(special C-4 rated SAE 30W weight only) . You see them in "slow speed" "off road" applications, (again special...

I decided to post a picture of the "innards" of an Off-Road Allison so people can see what I'm talking about. Sorry it came out at a funny angle, but you can clearly see the gears are helical gears just like a manual transmission uses. Also these transmissions do "not" go over 20 MPH on...

Having worked on off-road Allison transmission's I can tell you they have large Helical gears in there just like manual transmissions do which need extra "shear stability" . Your over the road transmission doesn't have large gears in them. They use Planetary gearsets only. Also that oil must...

Actually there's not that many opinions here. There's just a few that feel the military can do no wrong so why change it. Most believe the "manufacture" has the best advice for their product. After all "they" designed it and built it. I worked at a "Detroit Diesel Allison" shop in the...

The Allison was never made from the manufacture to run on engine oil. That was a "military" decision. A good Dexron III or better oil is so far superior to engine oil that it is not funny ! A transmission oil must be a "lubricating oil" and a "hydraulic oil" at the same time. Engine oil is just...

Oil changes on an automatic transmission help the gunk that gets trapped in the valve body to come out. Since the oil level usually comes to the bottom of the valve body, the gunk doesn't have gravity to help it drain away. Once the oil level drops, it drags out the oil in the valve body and...

The Allison AT540 series transmission is a great transmission. It has been working in trucks since 1970 now. The main reason they fail is lack of proper maintenance. This is the main reason most equipment fails. Since they are such a good transmission and are very strong, most people tend to...