5.9 magnum in a 79 3/4 ton truck

Hey guys I have a quick question that may be answered simply. I have a donor 99 truck and I am looking to swap the 5.9 in to my truck and use the fuel injection. Before I embark on this project I think I only have one hang up. My 79 is a manual trans, will my flywheel bolt up to the 5.9 flange and work or am I going to have to do something else with the flywheel. Also if anyone has any tips about this swap let me know. The donor truck is a perfectly running and driving truck at the moment so I am pretty sure I won't run into any problems as far as bad parts from the donor.

sorry guys I just remembered and answered my own question. I will have to find a flywheel from a 5.9 because it has the reluctor on it. Is there any other tips for this swap?

Do you plan to use the 99 computer and wiring? That's going to cause headaches.

The 99 systems will be looking for an auto trans and numerous emissions systems that the 79 doesnt have.

I plan on using the 99 wiring just because I already have the donor and it cost me little of nothing. I thought about trying to flash the computer as a manual transmission before I took it out of the donor just so its not looking for the auto transmission. I don't care if it sets codes for the EVAP system it shouldn't affect how it runs. Also I'm not completely sure if it even matters how it runs if it does not see a transmission other than if it is in gear or not possibly. I also am curious if it actually needs to see a speed sensor or not I don't think that the speed sensor would affect the fuel trim. I am not worried about having to pass any emissions testing or any of that. I actually have quite a bit of background working on these systems as I was a Chrysler tech for over 10 years til about 6 years ago. So I'm kinda trying to "dust" the cob webs off the brain here to remember what these trucks actually had to have to run right as far as the engine goes.

When I finished my v6 to v8 swap in my 97 ram about a month ago I eliminated the evap crap, it's not hooked up anymore and I just plugged the holes where it connected to the vacuum ports etc. Pcm doesn't seem to care and it runs great. I used a pcm from a 98 truck that had manual trans since my truck is manual trans. I talked to a guy who used a v8 auto computer when he did his swap and he told me the check engine light came on with auto trans codes since he was running a manual trans. But it otherwise ran ok he said. So I know you can do it.

That's kinda what I was thinking. I couldn't remember for sure if the engine itself would run any different without seeing the transmission or the speed sensor. I knew the evap would not affect it. Since this is a perfectly running and driving truck I thought about just unplugging the things I know that I will not be using and see how or if it even affects the fuel trim or how the engine itself runs. Like I said I don't have to worry about any emissions testing so I don't care if it sets codes. Thanks for the input. Is there anything else that I have to look out for that I might be missing?

I believe it was the 90-92 trucks that used a speed sensor that fit into the location of the speedo gear housing on the trans. That would keep the computer happy concerning the speed sensor, anyway. Gene

I swapped a 99 5.2 magnum into my 80's jeep with manual trans. I too thought I was going to use the ECU/wiring out of the donor 99 dakota. Not a good idea. To get it to run, you will need to spend a couple hundred having the ECU flashed as an auto trans ECU will be looking for the transmission. Also it will be looking for the body control module. In addition, the 1996+ stuff is OBD-2 and the wiring in an ugly rats nest compared to the 92-95 stuff. For my swap, after digging through the 99 dakota wiring I eventually scrapped it and went to the junkyard. I found a 1995 Jeep Grand Cherokee with the 5.2 and I snagged the engine wiring harness and ECU. The 92-95 OBD-1 harness is so simple it's a thing of beauty. After peeling it apart, I found the engine control section of the harness is almost entirely self-contained. I only had to too 2 or 3 wires up to my original harness so supply power and ground to it. By far the easiest EFI swap I have ever done. I found the 99 engine sensors have different connectors, so I went back to the junkyard and snagged the sensors off the throttle body, distributor pickup and the 95 has an extra coolant sensor the 99 doesn't have. I had to drill and tap a small hole in the intake manifold for that one. I grabbed the fuel injectors off the 95 engine as well, as I read they had a slightly different flow rate. Also found out through trial and error that the Grand Cherokee ECU is looking for a security module(engine would fire for a second then die), so I snagged an ECU out of a manual trans Ram. Also I found out the hard way that the auto trans flywheel pickup sensor will not work with the manual transmission flywheel. The sensor is too long, and by bolting it down, then hitting the starter, the flywheel ground off the tip of the sensor. While shimming it may have worked, I just bought a manual trans sensor. Got her all buttoned up, hit the key and she fired up and purred like a brand new truck. Took her for a drive and found it was stalling on decel when rolling to a stop because I did not hook up the speed sensor. Did some hunting, found a speed sensor that would work with both my cable driven speedometer and the engine computer.

EDIT: FYI, I believe the OBD-2 computers pull timing if they don't see the auto transmission.

Also the magnum has a different ballance than a earlier la. We put a 833 overdrive in place of the 518 in a 93. It took a bit to find the right combination of parts to make it work

The 5.9 Mag needs a 5.9 Mag flywheel, the 360 wheel will bolt up but it'll be way out on the balance. The 360 has considerably more imbalance than the 5.9 Mag. To get it to work you'd have to add weight to where the three holes are drilled out, or else drill directly across from them, to reduce the amount of factory imbalance.

R.

Ok so I have been away for a couple days and appreciate the input you guys have thrown out here for me. So far I haven't started on the swap itself yet. I bought a magnum flywheel today because I realized the balance difference from the LA and the tone ring issue so I think that is covered. Will I have to drill and tap holes for my clutch/pressure plate to work and if so is there a clutch/pressure plate that I should buy to avoid having to do that? I talked with the service manager who is a buddy at the dealership I used to work for about flashing the PCM to a manual transmission so I shouldn't have to worry about the auto transmission part right? I will look into those speed sensors that are driven by the gear and have the cable on them. I will certainly take a close look at the crank sensor clearance. I am still willing to try the 99 harness and PCM surely it can be done. I'm always up for a good challenge and if it can't be done I will bite the bullet and hit the junkyard for a 95 and older donor I suppose. Thanks guys keep the advise commin.

Was your truck originally a big block or small block? I could use your old engine harness???

my 79 is a small block. I have several harnesses for small block but no big blocks.

If you have a buddy who can do the recalibration for free, you can give it a try. However, the way I understand it, the OEM calibration is also looking for the body control module to verify the key against the VIN. If you can have the ECU reflashed to eliminate the security as well, then you should be in business.

While you can make the 99 harness work, once you start ripping into it, you may not want to. I'm good with wiring, have done several EFI swaps and decided it wasn't worth it. However that was also largely motivated by the fact that I didn't want to shell out 200 bucks to have the ECU recalibrated as I don't have any avenues to get that done for free. The ease of working with the OBD-1 stuff was worth it. Also, the OBD-1 engine harness has a wire that I ran to a light in the dash for the check engine. So I can cycle the key on-off-on-off-on and the light will flash codes back at me. With the 1996+ harness you will want to wire in the data link connector so you can hook an OBD2 code reader up to it.

In addition, the OBD-2 can always be recalibrated later on for engine mods, where the OBD-1 system I did can't. For my application that was not an issue.

Don't you need the OBD-2 to use the port injection? My understanding was that the OBD-1 was throttle body injection only.
I have OBD-1 for my coupe, but the next project will have a Magnum engine and I'd love to be able to use the port injection. Gene

Nope. 92-95 magnum engines were port injected OBD-1.

So, I can use my 90 OBD-1 computer to fire a port injection Magnum, or do I need the 92-95 computer?

A 90 computer would be for a TBI motor. Worlds different than MPFI

The factory fuel injection system is very complicated and not swap friendly. The simplest solution would be an aftermarket self learning and tunable system with a 4 barrel standard flange intake.

As for the flywheel. If you do not use the OEM system, you will not need the tone ring. Now you can physically bolt any combination to the crank and block. Just need to copy the 5.9L Magnum balance.

I had a local shop copy the imbalance of an B&M SFI auto trans driveplate. Then drill the same imbalance into a 318 neutral balance flywheel.

The 92-95 magnum port EFI computer and engine wiring harness is totally different than the old TBI system. While the 92-95 magnum system is the easiest to swap, and is OBD-1, nothing from your old TBI system will be able to be reused.

I knew the wiring was different, I also have a 93 Dakota. I guess I assumed when Mopar put in the port injection, and changed everything, they also went with the OBD-2 at the same time. Guess my brain was hoping OBD-1 throttle body would run the OBD-1 port injection if I swapped out the engine harness. Gene

Is there a particular year GM or Ford EFI system
that could be got from a salvage yard
that has already been successfully used on
1992-1995 Chrysler Magnum V8s?

Seems like my fuzzy memory vaguely recalls that someone
modified the guts from a Ford distributor
and fitted it to a Chrysler LA distributor,
then used it and the Ford mass flow sensors on a Dodge Magnum V8.

Using coil on plug
And doing away with any distributor
Would seem to be a further simplification.

If memory serves, the GM efi system has been adapted to the mopar V8 before because the wiring is well documented and recalibration of the ECU is well supported vs the mopar stuff.

https://board.moparts.org/ubbthreads/ubbthreads.php/topics/662655/1/5-9-efi-a-different-way.html

This is the old thread about using ford efi.
The catch was and still is the distributor.

So here a few weeks later I made the swap. I might say it was actually really easy. Much easier than I expected. I appreciate the tips they came in handy. I had to get an crank sensor and flywheel for the manual. Otherwise it was pretty much wire up about 4 wires through the PDC and fire it up. I have driven it probably 30 miles so far and I love the way it runs. I used the 99 harness and controller I was not able to get it reprogrammed yet but not exactly sure if I'm going to need to. Even the fuel tank bolted in with the fuel line out of the 99 with minor modifications. I have a couple wiring issues to clean up but I was impressed how smooth everything went and especially the way the truck runs now. I thought the LA I had was a pretty hard runner after I built it but this magnum is pretty sweet. Thanks guys for the tips and if anyone has any questions while this swap is still fresh in my mind feel free to ask.