2006 Ford Econoline 5.4

Repalced Transmission about 6 months ago.

Original transmission had failed and I purchased a rebuilt unit from a local company. No problems for 6 months.

Now this issue I am having, once the van sets 6+ hours the transmission does not engage in Drive. If I put the transmission in 2nd and go for a few minutes i can switch to drive with no problems at all until the van sets again.

Shifts perfectly once Drive engages Transmission fluid level is perfect and still of brand new condition. No codes set at all in PCM Or TCM.

I’ve even let the van idle for 20-30 minutes in the morning and still will not engage in drive until going through 2nd gear for a little while. Any input is appreciated thank you for any help on this situation.

 

Have a look at the torque converter and see if that's the cause of the problem.

 

Torque converter is the same whether you place it in drive or second.
Suspect there is a possible internal leakage problem that gets temporarily corrected until it drains again.