New to me 300CD - Transmission Woes

[JamesStein]

Just got my hands on a '84 300CD.. thanks CDN.

Has an interesting transmission problem.

About 78 miles into my 180 mile trip home the transmission started acting up. Cruising along at 70mph and suddenly the RPM's hit redline. I backed of the accelerator and re-applied and the same thing free-spinning. Shifted into neutral and back into into drive, no dice, still free-spinning. So I pulled over and stopped. Left the car running and shifted to park, then back into drive and the transmission engaged. However, now it wouldn't shift.. stuck in 2nd gear, top speed about 35mph at 4,000 rpm. So I pulled over again and shut down. Let the car sit for 10 minutes tops. Started back up and drive off. Now its shifting all the way to 3rd gear, but not past 3rd. Eventually it slips again and won't enage.

Gave up had the car towed home. Incidently this started after I pulled off and refueled. Literally 2 miles after I got back on the road is when it started.

Any thoughts?