I DO WORK FOR A LOCAL USED TRUCK DEALER, THEY CALLED ME ON A 1999 24V, WITH A 188K WITH UNKNOWN REPAIR HISTORY, THAT WHEN YOU START UP COLD IN THE MORNING THE TRANSMISSION WILL NOT SHIFT OUT OF FIRST GEAR AT ALL. THE MECHANIC THAT TEST DROVE IT THIS MORNING SAID THAT HE EVEN OVERREVED THE MOTOR TO 3500 RPM AND IT STILL WOULDN'T SHIFT, THEN AFTER A FEW MINUTES OF DRIVING IT SHIFTED AND SHIFTED FINE, I DROVE THE TRUCK THIS AFTERNOON AND IT SHIFTED FINE FOR ME. I WILL GO DRIVE THE TRUCK IN THE MORNING COLD, BUT I WAS WONDERING WHAT TESTS I CAN DO, OR WHAT TO LOOK FOR BEFORE I WASTE MY ONCE A DAY CHANCE TO EXPERIENCE THIS PROBLEM???

 

Check the fluid level first then the pump for operation.

 

Mine did the same thing when i put my after market trans temp guage sensor in the port on the line where the factory trans temp sensor was.If these factory temp sensors do not pickup any temp above 70 or 80 degres,they will not shift correctly,try a new sensor or check the wiring that goes to the old one.Hope this helps.