Tranny Swap

89 Dakota 3.9 2WD. Can I put a 3 speed in place of the 4 speed?

I have a dumb question stick or auto?

Not dumb. Auto

replace a 4 speed with a 3..... why? I have gone the opposite way before on an 88 D100.

Just asking because I'm coming across them more often than the 4 speeds.

You can, but the 4 speed auto is longer then the 3 speed auto of the same size (904/A500 or 727/A518).
My luck with used automatic transmissions aren't very good. I would spring to have the one you have rebuilt, or buy a rebuilt trans from an online source. Gene

That's what I'm leaning towards.

I haven't attempted such a swap, but suspect it could be done. Some parts swapping and perhaps a bit of minor fabrication may be required. The older 904's had mechanical speedometer drives. I think the transmission mounts may be in different locations. No idea how the computer would react to the transmission swap.

Some people buy a manual or video and rebuild the transmission themselves. The 3 speed transmission are rumored to be easier to rebuild than the overdrives.

With the 3 speed transmission, you may want to consider changing the rear axle ratio if you plan to drive it on the highway.

Personally, if it was my truck and the money was available, I'd follow Gene's recommendation!