Muncie Transmission Cleanup and Installation

Next on the project list is cleaning up the transmission before installing it back on the chassis. After all those years under the car that old 4 speed Muncie M21 transmission was looking pretty ragged. And quite honestly, chances are this old Muncie isn’t going to hold up very long against a fresh 454 motor pushing over 550 foot pounds of torque. I’m guessing that within a year or so I’ll have to get a more rugged transmission. With that in mind I’ve decided just to clean up the transmission and check out the internals for major problems.

So, here are few photos of the transmission and bellhousing right after they came off the engine (several months back). As I mentioned in my last update, the old bellhousing is being replaced with a new McLeod scatter shield.

    

After a quite a bit of time spent degreasing, pressure washing and scrubbing, I was ready to open up the transmission case to check things out. Additionally, the case had a bunch of fluid leaks so I wanted to replace all of the gaskets while I had it out of the car. So, here’s the patient ready for some attention. I was surprised how well it cleaned up with a bit of elbow grease!

Here’s a shot of transmission with the side cover removed. As evidenced by the dark brown sludge covering all the internals, fluid changes apparently weren’t high on the previous owners list of priorities. You can also see the shifter forks on the case cover…

Here’s a picture through the side cover opening of the internal gears. From this point I completely disassembled all the gears and removed everything from the housing so that I could thoroughly clean out all the gunk (already partially cleaned in this photo). In order to replace all the gaskets it was necessary to gut the transmission case almost completely! I’m not going to document the disassembly step by step, it just wouldn’t come close to covering the whole process. I suggest that anyone who’s considering doing this first get your hands on a copy of the “chassis overhaul manual” which documents the whole process step by step.

While I was at it, and since I had everything disassembled anyway, I took the opportunity to bead blast the housing using some glass beads I bought. Glass beads are nice because they are less aggressive, and therefore more forgiving on the aluminum housing, than the blast furnace slag I used on a frame. Essentially they leave the surface with a smoother finish.

After bead blasting, and after a very very thorough cleaning, I replaced the tail housing bushing…

As well as the rear seal.

Reassembly was a bit tricky, there are a lot of parts that need to be aligned just right to get the case back together, but after two days of playing in the garage I had it all back together. Here I’ve placed a new bearing retainer seal in place before reinstalling the bearing retainer.

  

After a few coats of clear engine paint it was time to get the Muncie mounted back onto the new scatter shield. Here I’m lowering it into place with the engine lift.

And here it is, installed on the chassis again! Once I get the driveshaft installed I’ll once again have a complete driveline. I’m debating whether I should paint the bellhousing orange or leave it as is. I’ve got a while to think about it, so I’ll leave that decision for later.