I'm having an issue with the '97 in my sig. The trans will shift great when cold, pulls hard and shifts perfect. But soon as the temps get above 140*, it will not shift out of 1st from a stop. Sometimes I can let it rev up close to 3000, and when I let off the accelerator it will drop into 2nd, but that doesn't always work, especially when the temps get closer to 160*. It will always go to 2nd when I manually shift to 2. Once in manual 2nd, I can get up to where it should shift to 3 and place the shifter back in D. Rather than shift into 3, though, it goes to OD and chuggs along from 30 mph until I'm up to 40-45 where it would, under normal operating conditions, complete the 3-4 shift.

Its been doing this for about a week now. I used a superchips tuner to scan for codes, and none were found. The ambient temps have been 90-100, but the trans has not gotten above 180.

There was an instance 3 weeks back where I was climbing a steep grade at a slow speed in manual 2, and the temp got to 200 at the crest. Cooled off on the descent. I don't know if this could be related.

The fact that it shifts perfect when cold, and no codes, leads me to believe that the PCM and wiring is all in good shape, but there is something internal which can't operate properly when the fluid thins out, or when the item itself gets hot. I'm all ears for things I can check.

 

It sounds to me like you have a internal leak and after the fluids gets warm and thin it can't build pressure

 

So, how could I go about diagnosing where the source of this issue might be? I could drop the pan quite easily if I knew what to check when I got in there.

I've never torn down a transmission before, so I'd appreciate any input on how to do it, and what to look for.