OK, here's the story. I bought this car from someone in Louisiana a couple of years ago. He had busted the oil pan on the car, and kept driving. 86's the engine, but the car did not appear to have any rust and also had service records.
He was coming through my area, and I agreed to pay him to tow it here. Unfortunately, when he got here, he had dollied it, with the rear wheels on the ground. Bummer.
My indy had an engine, and he installed it. ( Which, was lucky to say the least, as the oil pan was also cracked (due to moving) and while R&R the pan, noticed that the engine apparently had been rebuilt very recently.!!!
Fast forward. Money was short, and other circumstances dictated that this car needed to be on the road. The engine runs quite well (although I think one injector is not quite right) and with 3500 miles, it runs OK, averaging 27 MPG. It also have much better acceleration than my 87 SDL.
Now, when I first start it, if I put it into Drive, it slips to the point of not moving the car. If I let it idle for a minute or so, it will move the car. This happens in both forward and reverse. When the engine was replace, the transmission fluid was also changed. Now, the dipstick seems to have a lot of black, in addition to the regular red. At highway speeds, it seem to work fine, and also when it's warm, the signs of problems are not noticeable.

Suggestions or comments?
THX

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87 300SDL - 215K Miles !!
99 F-350CC Dually PSD - 190K
86 300SDL - 189K
All on B-100