I’ve got a 98 with about 210k miles on it (bought it with 170k mls) and over about the last 6 months the trans has been shifting very weird.

this is most noticeable when cold but right after startup and letting the car idle for a few minutes, I put it into gear and the car does nothing. I have to rev it up about 2500 rpm for it to engage into gear. The other symptoms I have is whenever I come to a stop (car warm or cold) the car seems like it doesn’t downshift and nearly stalls. After a few seconds while stopped the car eventually kicks into gear and it feels pretty harsh.

when I first bought the car the transmission never had any problems especially when coming to a stop. Trans fluid is still new-ish, very red and completely full (never needed to top it off. I’ve gotten a p0715 code only twice since I’ve had the car. Any ideas? Not sure why but I’m leaning towards replacing the torque converter.

 

Well, it could be communication problems somewhere. Your car as a A650E transmission. I kept a memo in this forum regarding transmission issues, someone stated that the electrical solenoid that controls the flow of transmission fluid to lock up the torque converter clutch is wired in a series with the brake light switch. So they actually stated believe it or not that it could be the stop light circuit switch. There have been cases apparently.

But you are also getting a speed sensor code P0715, that sensor is on the right side of the transmission I believe. If that is malfunctioning that also can cause weird problems such as hunting for gears or not shifting at all.

Just throwing out a couple of possibilities to look into before you tear everything apart. I believe you can test certain sensors with an ohm meter, check for damage or debris etc.

Image is location of the speed sensor to the best of my knowledge on the right side, I've never replaced mine on my car but they say that's where it is.

 

I’ve already replaced that speed sensor and inspected the circuit. Everything all checked out good but unfortunately I noticed no difference after replacing the sensor.

I have found some wiring diagrams however so i’ll definitely look and check out the circuit for the lock up solenoid.