Well, the transmission is fully electronic controlled and if the tcm sees something in it that it doesn't like it goes into limp mode. 90% of the time it happens after the fluid is changed. This is because whoever changed the fluid did not do a very good job at it. Either they forgot to put the new o-ring in or just did not fill it all the way. It went into limp mode because it sucked some air while the car was moving and didn't want air in the system cause you know what happens if air gets in your brake lines, if you don't just think of it this way, hydraulic fluid doesn't compress, air does, and the petal gets spongy. Well, the transmission uses shift valves and there cannot be air in them cause they will not shift properly so essentially the transmission is saving itself by only giving you 1 and 2 speeds. The only way of fixing this is to first get out all of the air from the system and then fill it with the proper fluid. Atf+3, +4, or +5 (I personally use atf+3 in mine with a bottle of lubegard atf protectant, its approved by chrysler and NATRA but thats just me, i like to keep my tranny working a long time, others may not) DO NOT USE ANYTNING EXCEPT THE RIGHT FLUID. Then you will need to take it somewhere that has the DRB II code scanner for the transmission and clear the code. If you have any problems, e-amil me at
Boogieman142@hotmail.com I have rebuilt a few of these 4 speeds and own one in my everyday car.