720 Gas to SD22 Diesel Conversion

[CJ7fun]

Hi all looking for advise: We have a 83 720 Gas 4X4 with a seized Z24 engine. I also have a 81 720 2wd with a good running SD22 and a rough body. My goal is to have a 4X4 diesel 720 for cruising the Oregon logging roads and minor Hwy travel to get to the logging roads (No Freeway speed needed, not with a SD22 :). The 4X4 has 3:89 axles and 30" tires.  I would like to use the 4X4 gas frame and move the frame pads for the motor mounts. (I am a profession tech, have hoist, welder and fab tools.) I am going to swap the engine, transmission, fuel tank, wire harnesses, cluster. My main concern is the oil pan.  Is there room to clear the front diff?  Has anyone else done this?  Would a custom oil pan and oil pickup tube work?  Go to a straight axle? (Not really making a rock crawler)  What else am I missing? I know there are lots of little things in a swap. Thanks, for any input

[620slodat]

Wayno (on this web site) is the SD-22 and SD-25 expert. He would be able to tell you if the oil pan will work with the stock independent 4 X 4 front pumpkin ((I don't thank it will work). He put an SD-25 (22?) into a 720 frame. I think that he went SAS though instead of independent suspension. He also put the diesel wire harness into the 521 cab, and put that onto the diesel frame. So, he is well experienced in what you are thinking of doing.

 

The motor mounts for the SD-22 are in a slightly different location than the gasser motors. I started putting an SD-22 into a 620 standard cab pickup. Then I was given a 720 long wheel base frame that originally had the SD-22 in it, so I went that way. By using a piece of 1/4" plate I was able to put the SD-22 motor on the 620 gasser motor mount. I don't remember the exact dimensions, but the gasser mount is somewhere around 1 to 1 1/2" behind the SD-22 motor mount. However, if you are a better welder than I am putting the motor mount in the correct location would be better than the plate.

 

I did not have the diesel wire harness, but I was able to get the SD-22 running, like from the factory, with a rotary switch from Radio Shack and the stock IP controller. I now have an aftermarket diesel ignition switch, which is still up in the air if it will work for me in the final set up. 

 

By the way, could there be a typo in your location? I couldn't find a Wilerville in Oregon, but Wilderville is just west of the Applegate River, and a little bit southwest of Grant Pass. I lived in the Grants Pass area in the early 70's.

 

Don

[wayno]

If you keep the stock drive train in your 4wd truck you will need to make or buy a custom oil pan, they had 4wd diesel 720s in Australia but I have never had any luck getting a response from any wrecking yard over there about any part, make a oil pan or convert over to a solid front axle, oil pan seems easier.

The 720 with an SD22 had 3.89 gears in the rear stock, but I would not expect it to push a heavy 4wd truck down the freeway at freeway speeds, it just doesn't have the HP.

I helped my friend turbocharge his 2wd 720 with an SD22 engine last Saturday, I was not impressed, the result was not even close to the result I got when I turbocharged both my SD25 engines, he says he has more power now, but I was not impressed, I need to talk with him more and he still needs an exhaust system.

It appears you have thought about this from your first post, I know a guy that has a 4wd diesel with the stock front diff as I recall, if you need photos I suspect he will let me take photos if he still has the truck, he had some health issues a few years ago and had to buy an automatic vehicle so he could drive, let me know.

I can say this for sure, the 4wd diesel oil pan is very strange looking, but so is the gasser 4wd oil pan.