Dodge Diesel - Diesel Truck Resource Forums - '98 12 valve no overdrive or lockup

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'98 12 valve no overdrive or lockup

my friend just bought a truck im trying to help him out on. every gear shifts fine except that it doesnt seem to go into lockup or overdrive. he already replaced the two sensors on the passenger front corner of the valve body. Is there any common things that could cause this besides maybe the od/ lockup solenoid?
the truck specifics are that its a 98 3500 4x4 12 valve engine. any thoughts or ideas of what to try are appreciated. also im pretty sure the transmission has been replaced at one point or another and it has roughly 250,000 miles on the truck

You need to hook up a pressure gauge and make sure it's going into OD. Had one that would do this and it was time for a rebuild.

TPS can be a culprit as well...

get rid of the TPS all together, do the potentiometer mod.. way better setup and alot cheaper. do a search and you should find it..