Overdrive

Same happened to my wife when shopping, turned out to be the 4th gear clutch pack. They repaired it at the dealer and flushed automatic trans and refilled.
Until it's fixed just keep OD button out and stay off highway. It cost us under 400.00 with the 98.00 flush.
I am now having problrms with 2nd gear hitting hard and slipping in 3rd only when cold. 4th still works like a champ. I am taking it to the dealer tonight and will let you know more when I find out.
1993 Mitsubishi 3000GT Base OHC Automatic with OD
103000 miles
Jim :D

We got the car back about 2 weeks ago, the dealer showed me a service bulletin from Mitsubishi stating this was a common problem with the 3000GT's. The shifting solenoids do not function well when cold causing this surge into second and the slip before third. Ours also has a momentary hesitation as it is shifted from reverse to drive and starts to move forward, almost like first gear comes has two stages. I was told the upgraded solenoids were no longer available. They did an entire fluid change by pumping the transmission fluid into a bucket and then pulling clean fluid from another, like a T-Tech but the service manager said that the pressure from the T-Tech is too high and could damage the system. They also installed a new transmission filter. Car is running fine, less of a hit went entering second, even less when it warms up. Hope this lasts.
Jim :D