SuperTruck: Mercedes Manual Transmission

by Ben N on August 7, 2014

A couple of weeks ago, I made a trip up to a salvage yard several hours drive away. The reason why is that I finally found a manual transmission that would match my diesel engine out of the 240D.

My original concept for the “SuperTruck” hybrid was to mate up the old 4-cylinder diesel to the Chevy stock 5-speed. Of course, I have NO idea how to actually do this.

On a web forum, somebody asked why I didn’t just use the Mercedes manual transmission. First and foremost, because they have been REALLY hard to find. Most of the old 240Ds were with AUTOMATICS, such as the one I got this engine from. Beyond that, I wanted to use the Chevy transmission because it would be easier to fix and find parts for, cost less, already has the right mounting points for the truck, and has FIVE gears instead of only four. Beyond that, the Chevy transmission also has a nice solid splined output shaft that should be relatively easy to connect to an electric motor. It also has the standard stick shifter that will fit right back in the truck, whereas the Mercedes tranny has an unusual set of three levers and rods coming off of it.

However, I was also a bit stuck on the project. I thought that if I at least had the Mercedes manual transmission to look at, it might give me some good ideas. Otherwise, I might also be able to take it apart and use just certain components from it. When I finally found a Mercedes transmission, I bought it.

So that’s where I am right now. I took a look at the bell-housings on both transmissions. The Mercedes is 5.5 inches deep and the Chevy is 6.5 inches deep. So, if I’m able to pull the bell off the Mercedes and put it on the Chevy, I have a spare inch to work with. That would be taken up by some sort of a custom aluminum adapter plate.

DSC_2461I sprayed down the interior bolts of the Mercedes manual transmission bell housing with some “PB Blaster” and let it soak for a bit. Next, I started removing the bolts with a 17mm socket. To my surprise, the bolts came out pretty easily. On the other hand, the throw-out bearing was rusted solidly in place. I have decided that I really ought to own a puller anyways, so I went to the auto parts store and purchased a three-clawed puller. It worked like a charm.

With the bolts out and throw-out bearing removed, I thought I could remove the bell, but it wouldn’t budge. I could now see there there were four small bolts that held in the collar around the transmission shaft. I removed those and then was able to split the bell off the transmission with a pair of pry-bars.

Finally, I could put the bell housing on the engine. Overall, it lined up rather nice, but not perfect. There were a couple of holes in the engine mounting flange that went to solid metal on the bell-housing. Oh well, it just meant that a few less bolts would hold on the manual transmission as compared to the automatic.

I already have a clutch disc and cover that fit the manual flywheel and Chevy transmission. I’ll need to get some replacement flywheel bolts. (Ones for a manual flywheel are SHORTER than for the automatic version!) I also need a pilot bearing.

Next, I’ll see about getting the bell-housing off the Chevy manual transmission and try figuring out what it will take to make a custom adapter plate to mount the bell-housing from the Mercedes to it.

I always feel good whenever I get a little something done on this project. It’s been slow, and feels WAY over my head in terms of skills and knowledge versus what I’ve done before, but I think the finished project will be totally worth it. I always gotta keep reminding myself that before I built an electric car, I had never built an electric car before either.

‘Til next time, stay charged up!

-Ben

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August 7, 2014 at 1:19 pm

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