Transmission Problem

My 90 Trooper has problems shifting into overdrive, Its an automatic and shifts all the other gears normal but not OD. It does seem like it will shift once it warms up (driven a long time) on the highway but even then it downshifts out of OD without cause. Anyone have this experience?

Could be a coolant temp sensor issue. Lots of cars wont shift into OD until the engine coolant temp warms up. Supposedly this is to *help* emissions by allowing the truck to warm up faster at higher RPM's while not it OD.
G/luck
Joel

i wonder if the sensor is on the trans or the same sensor as the water temp guage, the Haynes manual is no use.

I think you have 2 sensors both of which are on the intake manifold. IIRC, the one towards the front and the side is for the gauge. The one towards the rear and on the bottom (kind of have to feel for it rather than see it) is for the computer.

Thanks, exploring i will go
Have A Happy New Year!

A similar thread just came up here - http://www.4x4wire.com/forums/showflat.php?Cat=&Number=647044&page=0&view=collapsed&sb=5&o=14&fpart=1

Pay particular attention to the post by JLemond as he is probably the most knowledgeable Isuzu poster anywhere.

I'm on my third transmission now.

I'm on my third transmission now.

WOW! 3 tranmissions?!? I'm considering doing my first repair or getting a rebuilt tranny for my 91Trooper 159K 2.8 5-speed 4WD.

Why so many tran. if I might ask?