I have been researching the 3.9 to 5.2 swap for a week now. I have no oil pressure after 5 min of driving is why Im swaping. I think i understand most of it but I have never touched a dodge b4. I have a few questions from looking at the swap section.
1. What trany do I have (94 dak 4x4 auto). Will this trany be good for getting around town all winter and not beating on it? Shifts nice and firm no hickups at all. And this is just a winter truck to put my 72 Cutlass to sleep. from what I understand the flywheel teeth are atached to the TQ coverter? So I just use my V-6 conv and the V-8 crank wheel?
2. I can use the v6 comp but run 2 wires to the the other injectors. I took the 5.2 from a 95 jeep and have the entire engine wire harness. Can I get the factory v8 dak computer and use this harness or do I use the v6 engine harness and cpu? Might have more questions but these are my main conserns.

 

Also I believe I need to change the oil pan to. I am picking up a ram pan tomorrow. Will this work?

 

You probably have a 42RH. It is not intended to be behind the 5.2, and I would say it will go out. The 46RH tends to go out, so I don't think a 42RH has a fighting chance. I would sell it and use the money to get a 46RH, since it is working good you should be able to get some decent cash for it. If you destroy it you won't get much more than scrap money for it.

You need a flexplate, not a flywheel, and yes, the one you have attached to the torque converter should work since the 5.2 is also internally balanced. Somone check for me when they read this, but the torque converters should be interchangable between the 3.9 and 5.2, correct?

V6 computer will not run your V8. You need a V8 computer and the two extra wires. Yes you can use the V8 wiring harness you got with the engine and even the computer if you have it. I think the jeep computer should work for you, no need for it to be from a Dakota necessarily. So you have a choice, run the two extra wires or swap out the engine wiring harnesses, up to you really. Either way you need a new ECM.

No, the oil pan from a Ram will probably be larger, I think. At least depending on the Ram, a Ram 2500 pan looks to be larger. Best way to verify what pan you need is to call or go to napaonline.com and check the P/N for the pan you have in your truck with the 3.9 and the pan from the 95 jeep and your 94 dakota with a V8. See what P/Ns are from different years and you should have your answer.

 

So if I use the jeep computer I would probly loose my gauges? How do I tell the differences on Dodge transmissions? Can you look at the oil pans? Would the 46rh work with 4x4 and do I need to change the grive shaft? Hell I might try to find a decent 3.9 and sell the 318 lol. Now to find one without sludge lol.

 

If you don't beat on it AT ALL and its in good shape now, it should last you a little while. But I agree 100% that you should sell it now that its in good working condition rather than destroying it and then having to replace it. Because it will inevitably go out on you faster than a 46rh in the same condition would. And when it does, you won't get any cash for it.

Just to clarify... the flywheel and torque converter should work (I'm not 100% sure though). The flex plate from the v6 WILL NOT work. It has the wrong crankshaft position sensor hole pattern.

+1. I have a computer from a 1995 Dodge Ram 5.9L v8 running my 1995 Dakota 5.2L v8 and everything works as it should. So you don't need the computer from a Dakota. However, I'm not sure if a jeep would work or not. I'd go with yes, but don't hold me to that... its just a guess.

+1. You would need a Dakota oil pan. They are all different to clear different front axles, crossmemebers, steering components, etc.

There are 2 different 46rhs... one is designed for a 2wd, and the other for a 4x4. You would need one for a 4x4. Your original driveshafts should work just fine. There shouldn't be enough of a dimension different between the 42 and 46rh to stop your driveshafts from fitting. Remember, the driveshafts have slip yokes on them, so you have an inch or so of play.

 

I personally wouldn't let the transmission issue scare you off of the swap. YOu can sometimes find an engine and trans for a good price as a unit from somone, the only probem I see is that the 46rh trans does not show up as much.

Externally, the cases for the 46RH and 42RH are identical. It is hard to tell them apart. I believe you need to go by the numbers on the case if you don't know which is which.

Keep an eye open for a trans and you should be in good shape.

 

So with the 46rh do I need to change the kickdown cables (if they use that?) or will the wires and conectors work that same? Where are the codes on dodge transmissions? I think I almost got this figured out. Now I keep hearing i need 2 wires for the injectors. If I ust the v-8 harness and computer where would there be a need for new wires? Thatnks for all the help guys. Anynody interested in a good 42rh lol

 

Is there any direct bolt in upgrade? I noticed that Rams, vans, and jeeps all cary the 46rh. I assume all will work? Also seen some say 46rh-518? is there any difference

 

One thing I am not getting is the need to run 2 injector wires? If I use a V-8 harness and a v8 computer what are these wires for? Thanks for all the help