[]My 2001 60,000 miles 300M got overheated while I was on the road.The leaking water pump + an obstructed radiator + the thermostat were changed due to this problem ( Root causestill unknown for me) Prior to this failure (60miles before it happened ) I noticed that the car varied the RPM while going at 3,500 RPM on Autostick mode once. ( RPM suddenly decreaseddown to 3,300 aprox without releasing the throttle & then keep rising back to normal ) I use to shift 1st gear below 3,000 and 2nd & 3rd gear at 4,000 RPM's maximum.
The engine is not getting overheated any longer ( After 18 days at the dealer workshop ), however the RPM variation exactly at 3,500 RPM on Autostick mode keeps happening.The guy at the shop got the code P1797 (Manual Shift Overheat ) from the monitoring. They completed a transmission service without finding any residual part or "dirty" fluids. They do not know how to correct the problem. Theydid not propose to take the tranny down'cause theyarenot surewhat needs to be repaired.Is there anybody out there who can advice on this ? I would like to keepthe car for myself, but just like it was only a month ago....

 

NOTE: Low fluid level can be the cause of many transmission problems. If
the fluid level is low locate and repair the leak then check and adjust the
fluid level per the service information.
NOTE: Always perform diagnostics with a fully charged battery to avoid
false symptoms.
With the DRBIIIt, read the engine DTC’s. Check and repair all engine DTC’s prior
to performing transmission symptom diagnostics.
With the DRBIIIt, read Transmission DTC’s. Record all DTC’s and 1 Trip Failures.
NOTE: Diagnose 1 Trip Failures as a fully matured DTC.
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors.
Repair as necessary.
Perform the Shift Lever Position Test. If the test does not pass, refer to Symptom test
for P0705 Check Shifter Signal.
For Gear Ratio DTC’s, check and record all CVI’s.
Most DTC’s set on start up but some must be set by driving the vehicle such that all
diagnostic monitors have run.
Note: Verify flash level of transmission controller. Some problems are
corrected by software upgrades to the transmission controller.
NOTE: Check for applicable TSB’s related to the problem.
Perform this procedure prior to Symptom diagnosis

 

The people at the shop have access to the same info you have shared on your reply. They said they'd followed these steps. Is there anything else that should be reviewed ? Have you had a similar experience before with another tranny ?