Looking at a 79 SD 116...strange transmission problem???
 

Ok I am going out to look at a 1979 SD today(I've gone diesel crazy) that from the pictures looks to be in very nice condition...perfect interior, no dents, no RUST...the A/c apparently even works! One strange thing, the owner said that he just had the transmission fluid changed and since then the car is driving "strangely" in D. He says it drives perfectly in S, but D is not quite right. I won't really know exactly what that means until I see it, but I was wondering if anyone had any ideas? Is it possible that when they changed the fluid that something (vacuum?) became dislodged and is causing the problem? Thanks!!!

More detail is needed to yield any sort of assessment. Transmissions on these diesels can be very finicky... and can exhibit all sorts of offensive shift conditions without necessarily being ready for the scrapyard...