Before I begin- yes I did ALOT of searching on this topic before I posted so please help and don't tell me to search lol.

I have an 87 D100 Ram with a 3 speed auto transmission. Its fine around town, but on the highway it drinks gas and revs high- So I wanted to swap in a 4 speed automatic. I can't find anything about someone actually doing this on this truck- The guy at the dealership said all 4 speed trannys were computer controlled, so I would have to get the computer too. Has anyone dealt with this and can tell me exactly what I need? I would like to make this as simple as possible. Im not agaisnt a used transmission and computer. I really just want to do a straight 3speed to 4speed swap but its not looking that simple. Anyone with info please help. If I get a computer controlled, what exactly does it take to install? I am pretty mechanically inclined, but transmissions I dont know a whole lot about. Thanks guys in advance for any help!!

 

The 46RH is hydraulically governed. The computer controlled the lock up torque converter but that could be manually controlled by a toggle switch. My understanding is that this is not a simple bolt in but then I have never done it. Others can probably tell you more.

 

it may be alot easier and cost effective to change out the rear gears. if its reving high like you say,it must have a high numerical number rear like 3.91 or 4.10. the 2.76 or 3.23 may have been standard on this truck,3.54 and up being an option.just my opinion. what ever you may figure out,good luck

 

http://www.transmissioncenter.net/SwapInformation.htm

I have no clue if this is accurate, so use at your own risk.

 

I have personally done this swap to three ram vechicles--2 ramchargers w/small blks and a crew cab d200 w/a 440. worth every penny and the work. can sell you the parts needed and talk you thru the entire swap. Just get ahold of me. Will check this web site and e-mail tomorrow nite.

 

Did you see a gas mileage increase with the swap?

 

from the what i have found it should increase you gas mileage. if you are traveling down the highway your engine should be running about 1000rpm lower in OD than it would without it. i just topped up the ramcharger i bought and it got 14.1mpg with me driving it like a bit of a maniac while getting used to it. i think if i start driving it a bit easier and keep it all hi way miles i might be able to get into the 20mpg area.

 

Any increase in mileage will depend mainly on what kind of driving you do. Around town it won't increase but on the highway it will help.