98 gtp trans question

[tankerchief]

My auto 98 GTP has a trans issue. It has not thrown any codes yet. It used to shift from 2nd to 3rd around 30-35 mph at 2500 rpm. Now it will not shift till I go about 42 and let off then it will shift. If I am leaving a light or on an on ramp there is no issue as you are on it and shifts around 3k anyway. It is rfeal annoying when you are in a 40 zone and th rpms are 2800-3000 at 40. Then I go 42 and let off and it shifts just fine. Any idea what is wrong? Car has 136'000 miles

Next question, if my trans is bad what other year transmissions can I put in my 98. I might go the junkyard route to save some money. I have acces to a lift to make the swap pretty easy. What is the average time it has taken any of you to change out a trans?

Thanks for any info you may have to help me out!

[bstuby]

Mine is doing the same thing. Anybody have any help on this?

[SuperCharged0nE]

just bought a new GTP also (98) seeing the same problem.. and when I really get on it I red line like no ones business so I'm getting a little skeptical.. soo... I'm thinking about replacing the tranny also?

[BillBoost37]

OP...take a buddy with you. Get the trans to do this issue. Then go to the parts store w/o turning the car off, have it scanned. Most trans codes don't turn on the light and they also reset with each ignition cycle.