96 12 v,260,000 miles Well I have finally had a trans problem. No overdrive.
No lockup. Wired in a switch for lockup,that works but still no fourth gear.
If I lift off the throttle while in 3 lockup,the ol truck just coasts down the road,so I assume it is releasing the direct clutch,driving on the roller clutch,but not applying the O.D.clutch. However when this first started it was intermittent and O.D. engage speed had been creeping higher.So,have I cooked the O.D. clutch,had a solenoid failure or do I have a TPS issue?
96 12v 3500 drw 4wd 260,000 unmolested miles. Thanks in advance for your help.

 

Try to shift by hand and put it in N for a second or 2 before shifting in D