cobra tranny

Iv been posting msgs about my 97 gt I just swaped in a 99 cobra t45. I can get in go through first, second, a little into third and the car just dies it will do it in 4th and 5th also. so Iv been puzzled. I noticed third does it around 3500RPMS but its weird cause in second I can turn 5oooRPMS with no problem. well i put it on a scanner computer and no codes poped up. the only light that is on is the ABS light. My speedometer isn't working either someone told me it could be because the speedometer isn't regulating what its doing . could my abs have something to do with it? or whats the difference's between a 97 gt t45 transmission and 99 cobra t45 transmission. Are the speedos differrent im stumped
 
The 97GT T45 transmission has a mechanical speedometer and the 99 Cobra T45 has an electronic speedo. That is why the speed isn't working. I would try and get that speedo working because I think that is what is killing the motor.