3.0 to 4.0, new tranny or keep the old one?

[Zerocide]

So im looking into going from a 3.0 flex fuel engine in a 99 ranger to a 4.0 flex fuel engine from either a 2000-02 explorer. I figured the tranny should work fine but i read otherwise. my only real concern is that the 99 auto gots 3 gears compared to 00-02 auto having 5 gears. Even then wouldnt the computer swap fix that?

 

[Wicked_Sludge]

the bellhousing pattern is different between the motors, so you need to swap transmissions either way.

 

[Sevensecondsuv]

Well I can tell you for a fact that the 99 auto has more than 3 gears. It has 4 or 5 depending on if it's the 4r55e or the 5r55e.