Offroad-Express

i have got 1993 isuzu bighorn 3.1D. Only when i start the engine when the engine is cold and try to drive after warming up for 3 to 5 minutes, the transmission doesn't change to overdrive till the engine temperature gauge is about 1/4 up. Once the engine is all warmed up the transmission changes smooth as. the mechanic has changed the transmission oil as well as transmission flush, changed the transmission solenoids, mechanic also looked at speed sensor, changed hot water sensor, transmission fluid sensor, but the problem is still there. we have also bought a secondhand tranny for replacement yet to be replaced. Can somebody help me pleeease.

What gear is it late changing into...
Most electronically controlled auto's will hold back the OD until upto temp.
They either use a stand alone sensor or use the water temp sender unit.
You could also have water coolant / thermostat issues and it could be slow to warm up....

it only happens at the begning when i try to drive. once when the van is moving then there is no problem

Does it just shift later, or doesnt shift at all until its warm? Ie, my car when cold revs a lot longer before shifting gears, but is sweet after a few mins driving, but it shifts gears.

Peace

Arvin

it doesn't shift till warms a little bit. it does not slip. once warmed up it runs normal.