I drive a 1995 Eagle Vision. At 35,000 miles the transmission seemed to get lost between 3rd gear and overdrive at about 38 - 42 mph. A new transmission filter and fluid change seemed to do the trick, but now at 58,000 miles the problem has returned. What gives? Is there a transmission adjustment to be made? I would like to keep this car to 125,000 miles.
You said the transmission is getting lost between third gear and overdrive. Another word for lost would be "Hunting" when describing a shift problem. This means the transmission can't decide which gear it should be in. So it continues shifting back and forth while under a consistent speed and load.
Also, very often drivers confuse fourth gear (overdrive) with the application of a lock-up torque converter, which feels very much like another gear kicking in, but is actually the torque converter clutch locking the engine directly to the transmission. This aids in highway fuel mileage.
There are several possible causes to the shift problem that you've described, but if you're Vision was built prior to October 24, 1994, the first place to start is with Chrysler Technical Service Bulletin number 18-24-95.
It deals with the recalibration of the Transmission Control Module (TCM) in order to disable operation of the lock-up torque converter, and improve several other shift quality symptoms. Another problem that the TCM update should improve is the early deterioration of the transmission fluid between 15,000 and 30,000 miles.
This condition seems to coincide with your original problem being alleviated after changing the fluid and filter at 35,000 miles.