Wont shift into 4th gear (auto)
 

Can anybody suggest where I might start to look so that I can diagnose why it stays in third. Shifts up to third fine but stays there. Any suggestions?

is it like this all the time or just when you floor it? you do realize the automatic is only 4 speed right?

try pressing the "hold" button on the shifter.

Just regular driving it doesent pass 3rd no matter what I do. I have played with the hold button but still nothing.

i'm not too knowleable on auto transmissions in general but have you checked your auto trans fluid level or has the tranny been serviced recently? hard shifting, jerky....any other symptoms?

How many miles are on the chassis/transmission? Usually when something like that starts happening, its time for a transmission rebuild.

What does it sound like when you try.

Everything about the trans seems ok. Its is not jerking or acting irregfular except that it just wont go into overdrive. I am driving on the higway on cruise control and am at 3500 rpm at about 60 mph. It just wont engage the overdrive.

Yea, that's typically how they fail. They usually start engaging the upper gears more slowly than when they were new. Eventually, they just stop going into the upper gears. Take the car to a transmission shop and have it checked out. Any decent transmission shop will do as transmissions aren't a "rotary" thing.

hmmmmm...no noises.......no jerky feel......no hard shifting..... without looking at anything except those as indications i'd say you were having an electrical issue........speed sensor or solenoid in the tranny gone bad.

Any codes from the transmission ECU?

Run a jumper wire from TAT to ground in the diagnostic box, this will cause your hold indication light to flash just like checking for engine codes. Thats where to start.

it may be a problem with the transmission control unit. just like the ecu the tcu will give off codes. have a trans shop check it out. and at the least get it serviced with synthetic fluid it will give it a little more life.

Jeff