I recently had a piston and head burn up in my 4.7 (https://dodgeforum.com/forum/3rd-gen...y-guesses.html). I've done quite a bit of reading and I'm super close to buying a used 5.7 hemi for replacement. I've seen a few older threads on here about the conversion, but no conclusions.

I've found a complete 2003 5.7 engine with all accesories, ECU, TCU, and wiring harness. Both vehicles have automatic trans. Both vehicles are 4x4 and have manual transfer case shift.

From what I understand, the transmission should bolt up ok. I'm going to confirm that the donor vehicle has the 45RFE/545RFE transmission. Apparently the TCM tells it to be a 4spd or 5spd electronically.

Does anyone know if the motor mounts are the same for 4.7 and 5.7? They're pretty cheap to pick up used, but I'd like to know if I need them or not.

Also, I'm curious about the throttle / accelerator. I believe the 2003 started using the electronic throttle control so I'm not exactly sure if I need the donor throttle cable or what. I heard about some conversion kit from mopar but I can only imagine how much that costs. Anyone run into this?

Otherwise since I'm getting the computers and wiring harness, I'm thinking positive about this, but I'm sure there are a ton of things I could be missing. For what it's worth, most of my 2002 truck was assembled with 2003 parts.

Thanks for any help

 

Im not such about much on the swaps but I can say if you can find any HEMI that is 04+ then get that. Although the 03 can be hopped up performance wise, tuning options is the down point. Now if you only want an engine and never want to do any major upgrades then the 03 is fine. But also keep in mind tat some of the 03 5.7s also have valve spring breakage issues as well.

 

At this point, I just need an engine that runs good. I'll probably take my chances on the valve springs, hopefully it works out.

For the throttle, it looks like I'll just have to install the drive-by-wire style pedal, etc. I'm able to get the pedal assembly and APPS from the donor. Should be able to mount the new pedal, mount the APPS by the battery, join them with the cable and run the electrical wire to the throttle body.

Still unclear on the motor mounts. I'm able to get the ones from the hemi, but not yet sure if they will bolt up to the truck without fabricating anything!

 

Im sure they would bolt up as the frames on 1500 would all be the same for the most part (2wd anyway). I assume the manufacture would make them so they could drop wither engine on the frame.

 

Engine crossmember and/or mounts may be different, but the transmission is the same. 45RFE versus 545RFE the only difference is a flash programming on the ECU.

Resale on your truck is going to hit the floor if you swap engines - anyone running a Carfax is going to expect the 4.7, heck anyone looking at the under-hood stickers is going to expect to see a 4.7 as well. Do you have to do emissions testing? You may hit a snag with them too.

It may be a better financial move to just throw a junkyard 4.7 in it, then trade it in on a hemi if that's what you want.

 

I would assume so too, but I won't know for sure until I see it. Both are 4x4.

Hmm ok, I'm going to have to see what I can find out about the crossmember. I heard from someone in another forum that did the swap successfully so I'm hoping to get some insight from them. I was a little worried there could be an issue with the mounts.

I'm not super worried about resale. I have an suv and this is a second vehicle. I just really need a truck, but of course I want it to run good. I paid $3600 for this truck with 100k on it. It needed a water pump, muffler, and brakes to pass inspection. It came with a brand new set of 33in BF Goodrich AT and a 3in body lift. It passed inspection about 2 weeks ago, then kicked the bucket a few days later. In maryland, once it passes, you're good. You don't have to keep taking it in for emissions.

I'm really just hoping to get the engine in and have a working truck. Used 2002 4.7s are almost as much as the hemis I've looked at and are 100k+. I found some hemis that come with everything and they are lower mileage. I certainly wouldn't do the swap if I didn't have a bad engine. I do appreciate the heads up though.

 

Swap out the valve springs if you buy an 03 or 04 Hemi! 04 isn't as bad but many 03's drop valves. Changing the springs isn't hard or expensive when the motor's out of the truck. Took me 2 hours, including modifying the tool and learning how to use it.

 

Sounds like a good idea. I'm probably going to have to wait to see how much this it all going to cost beforehand. If things look ok, I'll go ahead and do them now. Otherwise, I might wait a few months.

 

I just looked in the part catalogs and it looks like the crossmember on the 1500 4x4s from 2002 & 2003 are the same (#52021334AC). That is good news for the hemi install. Thanks to weed for the part catalogs.

 

Well, the Hemi assembly gets here friday so hopefully we'll make good progress this weekend. I will post progress and any notes documenting the swap.