I just pulled my '81 Imperial out of storage. The trans required about 2 quarts of fluid to top it off. I used some of the generic Dextron III/Mercon fluid. It may be slightly overfilled.

Today I took it for its first long-ish drive and noticed the a bad shudder just after a light throttle upshift (when you would expect the converter to lock-up). Does not occur under harder throttle.

Do you think this is related to the fluid? Are these converters very sensitive to the fluid's friction qualities like more modern transmissions?

I think I'm a little overfilled.. Could that do it?

Need this problem to go away so I can drive it to the Nats!