Been working on an '83 300TD with 210K on the clock for a while now. The transmission was replaced about 30,000 miles ago and has always shifted really damn firm. Well yesterday when leaving a parking lot I shifted in to drive and started to take off. Got a few feet then suddenly the engine revved up and the car went nowhere. Shifted in to reverse and backed back in to the parking spot, put it in park, shifted back in to drive and it was fine. Still shifted real hard when I left the parking lot like it usually does. A few stop lights later when taking off, shifting in to second gear was totally unnoticeable. That seriously threw me off. Shifting in to third it slipped a bit before settling all the way in to third. Fourth gear change was unnoticeable as well. Shift timing seemed about normal. A few miles down the road there was another stop light and when taking off the transmission was back to it's normal harsh shifts. I pulled over and checked the fluid, it was fine. Clean, full, and unburned. Went to take off and it slipped so badly the car would barely move! A few moments later it started driving like nothing had happened. The flaring and super soft shifts kind of came and went until I got the car home, pretty much hit or miss.

So today I pulled the car in to the driveway to check for any vacuum leaks, although I'm inclined to believe with no vacuum it'll shift hard and too much will make it super soft and flare. Didn't see anything wrong. Went to pull back to where I have it parked normally and reverse would not engage. Instead I heard a whirring sound from the transmission when I tried to engage reverse or drive. I tried to get it to go in to gear for probably a minute straight. I shut the car off, put it in park, restarted the car, and viola it went in to both reverse and drive quickly. Once it was parked I tried engaging reverse again and it took a few seconds but it went in, same with drive. I checked the fluid and it was low so I added a little more than a half a quart and took it around the block. The flares were gone but it shifted a little smoother, actually it felt pretty nice... about a happy medium between slush box and neck-jarring.

I unplugged the two vacuum lines from the modulator on the top of the IP and plugged them. Drove it around the block again and the shifts weren't any different. That could be bad. But I don't really see why such a new transmission would suddenly start acting up, especially if the shifts were always harsh enough that there is no way any slipping was going on.

I'm in the process of trying to sell this car and either this is a sign that this thing needs to get the hell out of my life or it's become so attached to me that it doesn't want to go!

If I have to bite the bullet and put a tranny in this thing... well that just sucks.