Transmission is not operating correctly when cold. The RPM's are above normal operating levels prior to shifting. After the vehicle travels a couple of miles, all is fine. Normal operational RPM's are around 2000 at 70 MPH. Now it is 2500 RPM's. Had the catalytic converter changed out about 6 months as well as the solenoids for shifting. I put an OASIS computer on it but could not find anything out the ordinary. I'm thinking the converter may be going out again.

First check transmission oil level.
If the oil level is normal, it is possible either the transmission pump pressure is low, transmission solenoid may be bad, or clutches are worn. Have someone check to see if there are any diagnostic codes with an OBD code checker.

what makes you think there is one,? not in the traditional sense, no.
read the operators guide yet?,
notice that page is missing, (trans checks) there is a DTC for this.
to tell you its time, that is covered in the FSM.

its missing for a good reason, on many newer cars.

AF33-5 trans box>?
fsm quote ( only an ecerpt, not COMPLETE< READ THE BOOK.
Important: Routine inspection of the transaxle fluid is not required. Transaxle fluid inspection is only required if there is a symptom indicating a concern with the fluid.

1. Park the vehicle on a flat level surface.
2. Operate the vehicle in order for the transmission fluid temperature to reach the normal operating range. Specification
   Transaxle normal temperature: 60-70 degrees C (140-158 degrees F)
   
3. With the engine at idle, manual shift through all transaxle ranges and return to the PARK position. Leave the engine idling.
4. Clean any dirt or debris away from the area of the transaxle fluid level indicator.
5. Remove the transaxle fluid level indicator bolt (1) from the transaxle.
6. Remove the transaxle fluid level indicator (2).
7. Wipe away any transaxle fluid from the indicator.
8. Insert the indicator into the transaxle until fully seated.
9. Remove the indicator and inspect the level and the condition of the oil on the indicator:
   
   • Transmission fluid level at normal operating temperature (1)
   • Transmission fluid level if cold (2)
10. If the fluid level is incorrect inspect for the following conditions:
    
    • Fluid below level, inspect for a leak.
    • Fluid above level, inspect for contamination of the fluid.

Important: The tranaxle uses T-IV fluid, GM P/N 88900925 (Canadian P/N 22689186). The fluid is normally red in color. The oil may darken in color with more miles on a vehicle.

run the fault codes
the rpms change indicates a ratio change up then back down indicating a TR or VSS problem

Over Drive..... Generally speaking, overdrive (OD) is the highest gear in the transmission. Overdrive allows the engine to operate at a lower rpm for a given road speed. This allows the vehicle to achieve better fuel efficiency, and often quieter operation on the highway. When it is switched on, an automatic transmission can shift into overdrive mode after a certain speed is reached (usually 70+ km/h [43+ mph] depending on the load). When it is off, the automatic transmission shifting is limited to the lower gears. For an automatic transmission, it is almost always best to select overdrive and allow the transmission to control engagement of the overdrive. (It may be necessary to switch it off if the vehicle is being operated in a mountainous area or when towing a trailer.) With a manual transmission, overdrive should usually be selected when the average speed is above 70 km/h (approx. 43 mph).

This may apply. ...............................

Carry out the adaptation drive cycle road test:

Note: This process must be carried out in normal mode (not sports mode). On a flat road, the transmission fluid temperature must be above 60° C (140° f) and below 100° C (212° f) (vehicle at normal operating temperature will ensure that the transmission fluid temperature is above 60° C (140° f)).
9. Accelerate from rest with light throttle (do not exceed the upper rev limit in appendix 1). 1-2, 2-3, 3-4 shifts must occur with engine speed between the following limits:.
Note: Do not move the accelerator pedal during shifts.

• 3.0L VIN ALL 1800 - 2000 rpm
• 4.2L N/A Prior VIN M96321 1450 - 1600 rpm
• 4.2L N/A From VIN M963221550 - 1700 rpm

10. Continue to accelerate gently to 50 mph (80 km/h) so that transmission shifts into 5th gear.
11. Go into overrun and let the transmission shift down into 4th gear without braking.
12. Brake gently to a standstill and hold footbrake on for at least 15 seconds.
13. This process should be carried out at least five times.

Page 2 of 3 Bulletin Number S307-17
________________________________________________________________________________

Sounds like you should not be driving the vehicle at all until the issue is rectified.

Try changing the transmission fluid and transmission fluid filter. It is a fairly easy but kind of messy job. Just buy the new fluid and filter, Grab your metric socket set and go at it. NEVER WORK UNDERNEATH A HOT VEHICLE. You have to pull the transmission pan to do this job. When you break the gasket seal several quarts (liters) of transmission fluid will cascade down on you. Be ready for it. Don't forget that when it stops draining there is still a lot of fluid left in the pan. When you finish cleaning up the fluid clean the gunk out of the pan. Install the new filter and reinstall the pan with a new gasket. Do not over torque the pan or filter bolts. If you strip them out or break them off you will need professional help to repair it. Refill the transmission with fluid. It should take six or seven liters.

check fluid level, make sure proper fluid is in transmission otherwise take to trans shop to diagnse if level and type is correct(check at idle normal operating temp)

P0733-GEAR RATIO ERROR IN 3RD

Theory of Operation
The Transmission Control Module (TCM) constantly calculates the transmission ratio based on the input speed sensor 1 and 2 (N2-N3) signals and the calculated output shaft speed. The intent of this diagnostic is to detect if the transmission is slipping or an invalid gear ratio is present.

• When Monitored: Engine RPM greater than 450 RPM , output speed greater than 180 RPM , no N2 - N3 input speed sensor errors present, no gear selector lever errors present, no ABS system errors, and all wheel speeds above 450 RPM .
• Set Condition: No shifting operation and detected gear is not the actual gear. No shifting operation - detected (calculated) gear is less than actual (expected) gear, no plausible gear is calculated, actual turbine speed - calculated turbine speed is greater than 300 RPM or calculated transmission ratio is above threshold. During an Upshift detected (calculated) gear is less than actual (expected) gear. During Downshift - detected (calculated) gear is less than actual (expected) gear.

Possible Causes

• LOW TRANSMISSION FLUID
• OTHER TRANSMISSION DTC's PRESENT
• INTERNAL TRANSMISSION FAILURE

Always perform the NAG1 Pre-Diagnostic Troubleshooting procedure before proceeding. See: Transmission Control Systems\Testing and Inspection\Procedures\NAG1 Automatic Transmission

Diagnostic Test
1. CHECK FOR OTHER TRANSMISSION DTC's
With the scan tool, check transmission DTC's
Are there any solenoid and/or solenoid supply voltage DTC's present?
YES >> Refer to the Transmission category and perform the appropriate symptom(s).
NO >> Go To 2 2. CHECK TRANSMISSION FLUID LEVEL
Check the transmission fluid level.
Is the fluid level correct?
YES >> Go To 3
NO >> Properly adjust the fluid level.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1. See: Verification Tests\Transmission Verification Test 3. CHECK IF DTC IS CURRENT
With the scan tool, record the Environmental Data and erase Transmission DTC's. NOTE: If the TCM detects and stores a DTC, the TCM also stores the vehicles operating conditions under which the DTC originally set and is located in scan tool under Environmental Data. Before erasing any stored DTC's, record any available data to assist in duplicating the conditions in which the DTC originally set.

Using the Environmental Data recorded earlier, test drive the vehicle while trying to duplicate the conditions in which the DTC originally set.
Did the DTC P0733-GEAR RATIO ERROR IN 3RD reset?
YES >> Repair internal transmission as necessary.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1. See: Verification Tests\Transmission Verification Test
NO >> Go To 4

4. INTERMITTENT WIRING AND CONNECTORS
The conditions necessary to set this DTC are not present at this time.
Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.
Wiggle the wiring and connectors while checking for any possible open or shorted circuits.
Check for any Service Information Tune-ups or Technical Service Bulletins that may apply.
Were there any problems found?
YES >> Repair as necessary.Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1. See: Verification Tests\Transmission Verification Test
NO >> Test Complete.

Not sure on yours but on my vehicle, it doesn't shift up until engine reaches a certain temerature, and right now in the winter weather it takes a little longer. On mine it's normal.