Lock up before overdrive
 

I have been having issues with getting overdrive to work , done the pot mod over and over tried manually grounding the brown wire number 6 of 8 and nothing , very randomly when the truck is cold it'll go right in , as soon as it warms up it stops , also when driving steady at around 50 the locks up and overdrive will come in randomly while the tc is still locked , rebuilt trans , any one have any insight on this ? 97 cummins 47re thank you in advance

Put in a tc lockup switch?