I'm having aa slight problem with my trany in my 95 ctd in dont slip or any thing but it will not lock up on it's own. i have a switch that i used way back to keep trany from going in and out of lock up if i use it it will lock the converter and at about 60-65 mph it shifts into overdrive. all shifts are hard like always have checked for particals in the fluis and there were none fluid is not burnt but dirty . any ideas

 

have u checked to make sure the plug on the trans is still plugged in good? make sure the rubber coating on the wires is still there. what about trying to scan it for codes?