You could be correct that this may not be the right transmission for the car. I'm not sure exactly when the change was made to electronically controlled shifting. If your transmission has a large black shitch on the side of the case where the shifter linkage connects, then it is electronic. If not, it is mostly mechanical.
If the transmission is electronic, it will use two sensors for speed. One is toward the front of the transmission, and tells the computer the input (turbine) speed. The other is on the transfer case, and tells the computer the output speed. By comparing the two along with engine load, the computer decides which gear to command, and activates shift sensors accordingly. Late shifts would point to a failed or erratic sensor.
If the transmission is NOT electronic, this is a classic symptom of a bad vacuum modulator or a vacuum leak in the line leading to the modulator.
I might also suggest scanning the system for transmission codes.
Saturday, January 3rd, 2009 AT 8:19 PM