So I just bought an 03 Ram 1500 4x4 5.7 Hemi. I also have an 08 (same options) but was totalled by cab fire. I have recently learned that converting the suspension with the 08 lift will be a no-go. What I would like to do is swap the engine and trans from the 08 to the 03 (100k less miles). I know there are some differences (MDS etc.) but I do have the whole truck (less whats inside the cab) for the swap (wiring harness etc.). Has anyone done this or know if this can be done? Thanks for any help or input!

Well, I wouldn't say it will be an easy job. But, having the 2008 truck will make it a hell of a lot easier than not having the 2008 truck! My guess is that it is quite possible, but you'll have some wiring to figure out.

Service manuals are very useful for this and the 2003 version can be found here. For the 2008, you may need to get something from alldatadiy.com (basically the service manual displayed a little differently).

You should be able to take the 08 engine and trans, use your 2003 sensors, etc and drop it in. The only real differences will be MDS (which you will have to get rid of) and EGR (which 2003's don't have). The physical driveline is pretty much the same, the electronics are different. The 08 has a TOTALLY different communications system than the 03.

Will he be able to simply ignore the MDS components and install in his 2003, or will he need to disassemble the 2008 engine to install non-MDS components (valve springs, sensors.. etc? I am not sure of all the MDS specific components)..

I am just curious..

That is a very good question. It does seem like the way to go would be to just use the long block from the 08, and keep all the current sensors, wiring harness, etc. But I do not know what the MDS entails (maybe just programing?).

My bro finally called me back so I figured I'd let ya'll know what I found out. He said the internal differences on the MDS are the lifters and modules on each I believe. He said that the modules can be removed and plugged. Also something about maybe the cam and crank sensors being different but I can switch them. So it looks like I'll just be using a 2008 long block only.

I would take the lifters, etc from the 03 engine (I would takes this opportunity to upgrade cams, but that's just me, if you don't want to you can just use the 03 cam) and put them in the 08. If you remove the solenoids, you will have to plug them. From what I understand, if you use non-mds lifters the solenoids won't matter anyway (your 03 computer won't try to activate them anyway).

Here's a quick update. I did the swap last week, and everything went well. It started right up, and after about 150 miles still no check engine light. I had to use my original 03 wiring harness so there were some adjustments that had to be made to the 08 motor. I had to swap valve covers first, because the newer MDS Hemis use different coil packs and do not have plug wires. Then I had to cap off the EGR at the intake and head. I had to swap the throttle bodies. The only other differences were a few sensors that had to be swapped, as well as some accessories (alternator, ac compressor, starter). It was very easy...basically if the harness did not fit a part then swap with an old (03) part. I left all the MDS components as they were, and just left the harness unplugged at the back of the motor (03 harness has nothing to plug it into). Thanks for the help, and hopefully this thread helps others doing an engine swap.

Good work! No CEL is awesome.

I've done a number of swaps and builds in the "day." But today with the advanced electronics, I have problems trouble shooting CEL codes. Good job jkel1124