The Mighty Merc – M5OD Maintenance

While the 4R70W isn’t a bad transmission, and probably one of the few automatics that doesn’t piss me off, I still rather have a manual. After searching for a small block ZF-5 that wasn’t overly priced or broken, I came across a M5OD out of a 4.2 V6 truck from a ’97 F150. The 4.2 trucks use the Small Bock Ford bell pattern (have to drill out the top two bolts to 7/16”), and they have the shifter tower further back than the older M5OD’s. Which makes it fit nicely into the Merc.

The whole assembly came as a package deal with a manual shift 4406 transfer case and front DS (Score!):

Split it apart:

Drained the fluid and popped the cover to see what the shape of everything was inside. I got lucky and everything looks mint:

One of the big flaws of this transmission is that the rear plugs on the shifter like to leak, so I pulled them out:

And stuck some 5/8” freeze plugs in there with RTV to be double sure that the thing doesn’t leak in the future:

Now it is waiting on the bench to be stuck into The Merc.