MF 1855 trans fluid change

First drain a little off and look at it. If it hasn’t been change since 1978; it’s a good chance it needs changing ? I don’t know if there is a drain low on transaxle. You want to check for water, muddy or milky oil or sharp smelling oil. If it looks good and clear, don’t change. I’ve heard of a lot of failures after oil change usually by getting dirt in or disturbing residue.

There is a wide selection of suitable fluids. Massey recommended ATF type "A" (now Dexron) as the alternate for their house brand. Also acceptable is ATF type "F", 10W-30 motor oil, any of the house brands of hydro transmission fluid, and most quality hydraulic oils. Check the bottle for the Allison 3, or 4, or the Caterpillar T02 specification. The filter is a Wix #51410.

The drain plug is in the bottom center of the final drive. Fill though the dipstick tube, but it needs a vent opened or it burps at you.

I used Dexron in my 1655 (now 2055), as well as for the separate loader hydraulics, due to mostly winter operations.

As Hydronerd mentioned, if it's clear and clean, you can leave it be, but it is in a gear box with all the gear and bearing wear that goes with it. At least change the filter periodically. Mine saw heavy work for over 24 years, and the hydro fluid and filters got changed every 400-600 hours (4-6 years). The loader gets it's fluid replenished as it leaks out when a hose fails, or due to the normal slight weeping at the rod end seal. The filter gets changed every 10 years or so.

Your transmission is a Sundstrand Series 15 Inline Type. The part number is 90-xxxx, not to be confused with the Sundstrand Series 90 hydro in 50-90 hp utility tractors.