I have a 91 Galant with 87,000 miles on it. Brake light came on three weeks ago. I took it into garage to check light and do scheduled oil change and trans fluid change. Garage did trans flush even though I told them not to and could not find any reason brake light was on. They said the trans needed to be rebuilt. It was sluggish before I took it in but now it is worse. Once I hit 30-35 mph, it shifts into neutral. Checked the trans fluid level and it was to the top of the dip stick. I took it back to the garage. They drained a quart of fluid and added a trans additive. Brake light is still on.

I saw some forums about switching overdrive off and gave it a try. When I turn the overdrive off via the switch on the shifter, everything runs fine although at higher rpm.

Is this really the trans needing to be rebuilt? What else could it be?

sorry but it looks like that is the case. however if you find out how much it will cost you to get it rebuilt i can find out if it would be worth it to just put in a used transmission. http://www.car-part.com/ you can find some super cheap tranny's there. so just e-mail me if you want me to help you out ok? LATER!!!!

Yes the 4th set of clutches for the 4th gear engagement is out, thus when the gear is trying to be selected the friction plates are too worn out to grab and engage the 4th gear , thus taking the over drive swith to off the trans ecu cancels engaging firth gear and overdrive . rebuilding is a good option , and should not cost that much , thius ive done may . Altho where yu are i am not sure . If yu are looking fpor a used unit there are many models that has an F4A22 transmission that yu need.