Engine light came on the same time this occured. Maybe a connection between the two ? We've 203,000 and are not too thrilled with a pricey tranny job. Otherwise it's a super car and in great shape !
Thank you for looking,
Marty

 

Took out the battery and cleaned up around the shift lever and (knock down lever?). We've had trouble with that before. Put everything back together and it worked perfectly until about 6.5 miles and then it shifted down one gear and the check engine light came on. Almost simultaneously.
Am i missing something with this transmission. The manual says it's a 3 speed. When I put it in "D" I consider it first. Then it shifts 3 times from there.
I'm going to stop by Autozone for a diagnostic to see if we can narrow it down. The problem seems to be electronic in nature.
I know someone here knows what's going on. Thanking you in advance,
Marty

 

the 4th shift is the lock up torq converter locking up...

 

yep I agree, theres a plug right in front of the tranny housing (its round I think) that needs to be connected for the lock-up. It was Dodge's way of avoiding a more expensive 4 spd auto and saving MPG at highway speeds. I left mine off when I did my valvebody swap, and the check engine light came on.