So I bought a 02 SL2 with 60k miles that needed a tranny. I put it in the shop to have the trans replaced. When I go to pick it up, I initially drive away satisfied because the new trans shifted really smoothly. However once it got to normal operating temps it soon started to shift rough and at higher rpm's until it eventually wouldn't shift at all out of first at all. So I gave it back to the mechanic and he replaced the trans and he says its the same result. It won't shift when hot. Has anyone had this problem. What could it be?

 

The service literature that I have for that model indicates that there is an extensive re-calibration procedure and diagnostic procedure for that particular year to insure proper shift point and operation of that transmission. It involves some scan functions to look for error codes, either a manual over-ride of recalibration based on road testing or resetting using a scan tool of some form.
These procedures are emphasised to have to be followed when making major repairs and or replacement.
I have no particular first hand knowledge of the transmission myself, but electronic controlled transmissions can be a bit spooky to work on at times.
When something his complex is included in servicing literature there usually is a reason for it.
The indication that two transmissions are performing the same seems to indicate that maybe something of this nature needs to be investigated.
The only thing that I can generalise at this point is the initial start procedure is (when a transmission is replaced or repaird) is to make a series of road tests starting with partial throttle proceeding to full throttle in a sequence of tests once the transmission has warmed up completly to insure the soft ware learn the proper procedures to deal with the transmission.
It also stresses re-setting error codes with the scan tool which also can be done by turning off the power, which in this case can be done by disconnecting the battery to reset the computor that runs the thing.
I would imagine further information can be found by purchasing a generic service manual through an autoparts store, a Saturn manual or something from Mitchels if you can find them and local libraries have them on file in some cases.
Dunno how much good this actually is, but hope it helps.