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2003 4.7l swap to 2003 5.7L

Discussion in 'Tech Info' started by tlcservices19, Oct 12, 2019 at 7:50 PM.

  1. tlcservices19

    tlcservices19 Junior Member

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    Hello everyone. I hope im not beating a dead horse here but i cant find the info that im looking for. I have a 2003 ram 1500 4.7L 4 wheel drive with manual shift transfer case. The 4.7L took a crap on me for the 4th and final time. I lucked up on a 2003 wrecked 1500 with a fresh jasper Hemi in it. The transmission in the donor truck is a 2wd. I know that the transmission bolt pattern is the same and the 5.7 will drop into and bolt up to my existing 4wd transmission but the 5.7l has a TCM and the existing 4.7l transmission is controlled through the PCM. Does anyone know if its just a matter of using the PCM,TCM, Instrument cluster and engine wiring harness from the donor truck or is there more wiring that has to be done? Both transmissions are 45rfe 4 speeds. It looks like i also need to change the Power Distribution/Fuse box under the hood too. Neither truck has factory security installed. I'm sure that this has already been done for this year but i couldn't find a write up. Any help would be greatly appreciated!

    Existing truck- 2003 ram 1500 4.7L 4wd manual Transfer Case

    Donor Truck- 2003 ram 1500 5.7l 2wd with external Transmission Control module
     
  2. Fast69Mopar

    Fast69Mopar Senior Member

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    You will need the PCM, TCM, Instrument Cluster, ABS Module, FCM, complete wiring harness, exhaust, oxygen sensors, front drive accessories, radiator/hoses, power steering lines/hoses, airbox.

    Now, for the transmission, is the transmission in the wrecked 2003 donor truck a stock unit from 2003 or does it appear to have ever been replaced with a reman unit or overhauled?

    If the transmission in your current truck is in good condition I would just leave it in place. There is absolutely no difference between the two. The difference is in the programming. When you install the 5.7 wiring harness and the TCM, the programming in the TCM will now make your trans a 545RFE. The difference in the programming goes like this...

    For the 45RFE, 4th gear is obtained by engaging the Overdrive clutch and the 4C clutch.

    For the 545RFE, 5th gear is obtained by engaging the Overdrive clutch and the 2C clutch.

    Mechanically there is no difference between these two units that you have.

    For the torque converter, if you are going to retain the stock converter, use the converter that was originally installed behind the 4.7

    The 2003 MY 4.7 torque converter has a higher stall speed than the 2003 MY 5.7 torque converter. If you use the converter from the 5.7 truck your off-the-line performance will suffer a little bit due to the lower stall speed.
     
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  3. tlcservices19

    tlcservices19 Junior Member

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    Okay. So entire engine bay and outside harness? How about instrument panel harness? Thanks for the thorough response.
     
  4. tlcservices19

    tlcservices19 Junior Member

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    Front of donor truck picture ...sounds like it be easier to just use my good truck with bad 4.7 engine to convert the donor to a 4x4, transfer all body parts and get it painted...I was going to paint it afterwards anyways. So basically swap donors lol

    994CFD35-3612-47E9-BD02-DAA1E00453ED.jpeg
     
  5. Fast69Mopar

    Fast69Mopar Senior Member

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    Which truck has the better interior?

    How about the condition of the instrument panel?

    Which frame and diff's have the least amount of miles on them?

    Do you absolutely want or have to have 4WD?

    I'd keep the 2WD HEMI truck together and put the good body parts on it from the 4.7 truck and then later on if you wanted to then swap the 4WD parts over. That way you can get up and rolling as fast as possible.
     
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  6. tlcservices19

    tlcservices19 Junior Member

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    I’m going to give the trucks a thorough inspection and make a decision on it according. I really do appreciate the good advice. I’m a master ASE certified tech of 25 years and own my own shop but your advice helps me to save a lot of time and head banging. It’s very valuable! One question though..if I decide to engine swap, must I also replace the instrument panel wiring harness as well?
     
  7. tlcservices19

    tlcservices19 Junior Member

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    Well I thoroughly Vetted the donor truck this morning. Front and back Suspension is shot, fuel tank has a leak, bed has a hole in it underneath the liner and it needs brakes all the around. Also the dash is completely toast, both airbags deployed, carpet is a mess and both front seats are toast as well. Seeing as how I’ve already addressed most of this on my truck I’m going with my original plan of the HEMI swap. Also, I visually inspected the instrument cluster harness main bulk connector where it connects under the dashboard after coming through the firewall. It’ll connect but I guess I might need to pull a pin diagram and make sure.
     
  8. Fishstickz

    Fishstickz Senior Member

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    Definitely check the wires, because, at least for later 3rd gens, there is a few of Hemi-specific wires and splices that run around under the dash. On the other hand, if you swap the wiring harness, the 4wd wiring MAY not be there. I'm not sure if the wiring for 4wd would be present on a 2wd truck
     
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  9. ric3xrt

    ric3xrt Senior Member

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    Both trucks being 03 you will be fine.
    The instrument cluster is the same for in 2003 for 3.7/4.7/5.7/5.9(V8)8.0(V10) trucks the odd issue is Manual door locks vs Power Locks..Not sure what the deal is, I just know there were/are two different instrument clusters.

    It's the under hood harnesses and ECUs that are different and were the swap nightmares can happen....done plenty of V6 to hemi, 4.7 to hemi and one Hemi to 5.9 Magnum swap. and the TB is Fly by wire on the 5.7 while the 4.7 is cable.
     
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  10. tlcservices19

    tlcservices19 Junior Member

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    Thanks guys i really appreciate it. I'll let ya'll know how it goes.
     

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