Sorry Eric, I didn't intend my comment to come off the way it may have.
If you disconnect the electrical plug from the left side of transmission, you should be able to drive around just fine as a 200-4R will not care if gas/diesel in reguards to lock up function info back to the ECM or it's apply during a disconnect.
If your Torque Converter Clutch is engaging once shifted into second but won't release without jerking your head loose coming to a stop, you might find the trouble inside the valve body shift train, early '80's 350 diesel powered cars/trucks had so many different hands in the pie at GM trying to deal with drivability issues between car makes using the diesel with: TH200C/200-4R/250C/325/325-4L/350C, ie: Buick,Cad, Olds, Pontiac cars in both front wheel/rear wheel drive models, with Chev/GMC trucks using TH350/375/400 rwd models.
Many techs found it easier to just hydraliacally lock the TCC once in 2nd gear and above, GM offered many different pressure switches for use in the 200 three speeds on the governor pressure tap(37-53 psi) as I recall being available/adaptable to the 200-R4/325/350/700's back in the day, not that I would have ever wasted my time trying to appease GM customer satisfaction/ warranty complaints. There might be a few at GM Powertrain that remember me, especially when it came to the 440T4/4T60 repairs in the late '80's early '90's.
I think my code name was K7535 back then, lol
Kevin.