Transmission swap
 

I recently bought a 1990,2500,4x4,w/6.2 diesel. it has a 3 speed trans. and sounds like an airplane at 70 mph. does anyone knw if it is possible to put an overdrive trans. in it and all the electrical work right with the shifting? any help would be great. thanks. Also this truck is the Z71 package. I have never seen a 2500 Z71 in this year model. Has anyone else? I thought the Z71 came a little later?

do you have a 3 speed auto or a manual trans???

its a 3 speed auto.

Sounds like a 400 turbo what is the tach reading at 70mph??? these truck start to guzzle fuel at them speeds or faster

yes I think it is a turbo 400. does not have a factory tach. so im not sure of the rpm. It just seems like it needs another gear. I know the computers on these trucks are kinda sensitive so I didnt know if i could put a overdrive in it and everything work properly?

Im not positive but you might be able to but the SES light will stay on ??? do you still have the muffler on the truck?if not you just might be experencing what 6.5 owners refer to as droning =airplane like sound

yes the muffler is on it still. Its all stock, the best I can tell. Any other pointers on getting a little more horsepower or torque? I dont want to modify it to much but anything simple or minor to get a little more get up and go?

You could try and find a intake and exhaust manifolds along with a turbo off a 6.5 that would wake it up a bunch and would be the least expensive route compared to a Banks system.