Not sure what would cause a first gear only condition. A B2 piston failure can often cause a tranny to NOT want to go in first, and then do better in higher gears.

The B2 is real easy to check. I'd do this before I condemned the whole thing. There is a access port on the passenger side rear (round, about 3.5" in diameter) that will allow you to pull the B2 piston out and get a look at it. This CAN be done with the transmission in the car, though you will be working by feel. It's much easier if you have another transmission around you can get a look at first, or at least some diagrams of what is where.

If necessary, yes, it's really pretty easy to pull the transmission from the car with the engine still in place. The toughest part is getting the bell housing and starter bolts loose for the first time. They can be in there pretty tight. Helps to have some good ground clearance to work with. If you've got a hoist, or some other way to get the car a couple of feet off the ground, it helps.

If you do end up replacing the transmission, be absolutely sure the torque converter is fully seated on the input shaft before you bolt things back together. It might seem like it's all the way on there and not be. Good way to ruin a front pump. Don't ask me how I know. With the bell housing up against the block, there should still be a little free space between the torque converter tangs and the flexplate. If it seems tight enough the flexplate won't still turn, the torque converter still isn't seated all the way.

I've replaced transmissions four times now on a 1984 300D. The first time took most of the weekend from start to finish. By the last time, I could go from pulling the car up on the ramps to beer in just over 3 hours.

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Gary Thompson
Georgetown, TX
1995 E320
1984 300D