I have a 98 ram 1500 with the 5.9 liter engine and I'm having trouble with the transmission. Trans would not shift gears correctly so I adjusted the TV cable. Now trans will shift but will not go into overdrive. When on hwy truck in turning about 3k rps at 70 mph. First thing in the morning trans will shift into OD but as soon has it gets hot it drops back down into drive and stays there.

Fluid is good.....

Does anyone have a clue what is going on .....

 

It could be your torque convetter or that you have o/d turned off if you have the option

 

If the fluid is getting TOO hot, the PCM will disable O/D, and the O/D Off light should come on.

If you aren't getting that, are you getting a check engine lite??? PCM should whine about it if it doesn't see RPM drop when it commands 4th gear, and TCC.

 

I will check codes and report back.

 

Could be leaking overdrive piston seal too. Because when the seal is cold it hold fluid pressure to apply the piston for overdrive, and when the fluid get hot the piston loose fluid pressure.