I have a '90 V6 Spirit and while driving highway yesterday the car made some violent mechanical shaking, 'check engine' light comes on and then all of a sudden started to down shift and would not go into another gear when accelerating. I drove over and turned it off. After awhile I turned it back on and drove off however more gently and gears shifted normally, getting into the 65-mph range. I took a loop and it started again with it downshifting, turned it off. Started again, shifting upward normal, but only went in 40 mph-range for a couple miles until reached destination. Did check trans fluid and was normal. Tried to leave destination and drive with it but even getting in 25-MPH range caused violent shaking and engine light to come on, so put up white flag and called AAA. I know very little about transmissions and was just asking if anyone can explain issue, and what will take to fix it. I have at a shop now (but won't be got to for awhile) but I just don't want to go blind into this. I appreciate your response.

 

Are you sure it is a trans problem?

 

It is my impression it is the transmission. The car accelerates fine and goes into gear normally, just after awhile you feel its hesitance when accelerating to maintain speed then the violent shake and deceleration. I don't interpret engine trouble. It has 85K on it (a granny car, I bought it at 25K in '04). Thank you for responding.

 

What engine does it have? Is it DIS?

 

Mitsubishi v6 3.0 not sure was DIS means.

 

Distributorless Ignition System. Which it probably is.....

Check your spark plug wires, and inspect the coil packs, see if any are damaged.

 

They are not DIS.
It sounds like something let loose, potentially torque converter bolts, or something internally in the trans.

 

You should have checked codes.

http://www.allpar.com/fix/80s-codes.html

 

Agreed. It's very easy to do, cycle key on-off-on-off-on (without starting engine), then the CEL will flash. Usually you'll get a code 12, you problem codes, then a code 55 is like an end code.