720 Gas to Diesel Conversion Bits

[abumariah]

Hey guys, great forum!

I just bought (last week) an 85 720 KC 4x4 (i've wanted one of these since i was a kid) with a perfect body and frame and a bad transmission. Right after i bought it i found an 81 720 kc 2wd diesel near me with a good engine (75000 miles) and transmission and a bad body and frame.

I want to swap them. I saw that someone on here was contemplating the same thing this past fall...did it ever happen? I'm currently working on getting the bad tranny out of the 85 so i can either fix it and put it back in while i'm parting out the 81 (small garage) or leave it out and pull the engine now too and do the whole mess at once.

If any of you guys have any tips for me, i would greatly appreciate it. i'm going to be diving into this starting tomorrow so i'll post back with any things that i learn along the way.

looking forward to getting to know you guys!

[asavage]

The "diesel engine into gasser chassis" topic already has two threads going: Engine swap 2006, and Engine swap 2007, and you might want to read what's been written there first. I'm doing an '82 SD into an '86 gasser myself right now.

I just bought (last week) an 85 720 KC 4x4 (i've wanted one of these since i was a kid) with a perfect body and frame and a bad transmission.

Transmission info is here. In particular, note that yours should have the larger front CS brg -- which you will not be able to retain if you go with the diesel swap:


Thread with this pic

Right after i bought it i found an 81 720 kc 2wd diesel near me with a good engine (75000 miles) and transmission and a bad body and frame.

I want to swap them. I saw that someone on here was contemplating the same thing this past fall...did it ever happen?

The only member I know who's done this is George. It's been done by at least two others that I know of. A custom, and I do mean custom, oil pan and oil pickup has to be constructed to make it work. You have to use the front case half of the SD's transmission, with the rear half housing and at least the tailshaft of the 4WD's trans.

I'm currently working on getting the bad tranny out of the 85 so i can either fix it and put it back in . . .

If you don't have a Factory Service Manual yet, get one! You will find it a wise and cheap investment in the long haul. You'll want an earlier one ('81 or 82) for the SD engine and controls, and a later one for the 4WD stuff.

See the eBay FSM thread for current cheap offerings.

Welcome to our Sandbox!

[bacho]

Hey, I have just started this swap. I have an 82 donor truck and an 85 4x4, both kingcabs. The transmission from the diesel appears that it will work with no problem, I dont see why that needs to be bothered with. The oil pan is the reason I got on here, does anyone buy the oil-pans from canada? Diesel 4x4's were available in canada so the oil pan and pick-up seems like a good thing to try and get ahold of.

I alot of expeirence with nissan 4x4's. I have a drop diff kit that I can use to drop the diff of the 720 4" along with a .75" drivetrain lift and the oil pan will clear the diff without being cut. I am considering this option because it would be cool to be one of the first to do it to a 720 but I dont really want to lift it 4".

[asavage]

I had in mind that the 4WD trans' tailshaft is shorter. But I admit I don't know; I am not really a 4WD kind of guy.

[bacho]

It may possibly be, I have not measured the exposed shaft. But on that number you can just use the diesel slip yoke and put that onto the gas u-joint. Appears to just be 1310 joints.

[abumariah]

hey guys.

thanks for the introductory info. i did read those other two topics in full. some great information there.

i'm planning to retain the sd22's transmission and put both of them in the 85 together. so it looks like my biggest problem will be the oil pan...except...

my sd22 doesn't have power steering or ac. does anyone know if its possible to bolt them on?

[bacho]

My Sd22 has AC, you should be able to make a bracket for that. I doubt the PS will just bolt on, although I have not really tried to see if the PS will work or not yet.

[asavage]

my sd22 doesn't have power steering or ac. does anyone know if its possible to bolt them on?

I just parted out an '82 SD22 with factory A/C. I have the compressor bracket, idler bracket (and the idler, which has a bad $6 brg) & the compressor. PM me if you are interested.

The truck isn't scrapped yet, though it's no longer in my possession, so if you needed the evaporator, condensor, or lines, I could be persuaded to go out in the snow field and pull them -- those parts would be "free", but you'd have to pay for my time to pull them and box them up. The A/C was not cooling in that rig when I scrapped it, but the A/C system was complete. I assume your '85 is already set up for A/C? If that's the case, you don't want any of that junk. But the SD A/C brackets are fairly rare around here, which is why I saved them. The factory A/C setup has two separate brackets.

I don't have a spare A/C crank pulley though, not right now. If you want to swap the crank pulley with me, I'd do that. It has an extra belt groove.

Power Steering: I can't help with that. I think you are going to have a tough time fitting it all in. Philip, can you point us to the pics of the SD PS setup that you had?

I will see if I can find the pics someone took of the customized oil pan for 4WD use in a Nissan chassis. I don't think he posted pics of the pickup tube though.

[abumariah]

thanks for the help! I wonder if i can fabricate a ps bracket and stuff it in there somewhere...those are pretty big tires on the front...

[asavage]

Philip's '82 has A/C, and it's in very good working condition. Pics of his setup are in this post. You can see the compressor easily; what's not clear, because the belt is removed, is the idler pulley & bracket clear on the other side of the engine. That bracket fastens to the side of the IP timer cover.

The lower radiator hose is a two-piece affair on the SD w/A/C, with a metal 90° connector in the middle. This picture is of the A/C-equipped '82 SD, with the compressor and bracket removed:

(click on image for larger)


If anyone's interested, I can pull out my salvaged brackets and take pics of them tomorrow.

[philip]

I don't have a spare A/C crank pulley though, not right now. If you want to swap the crank pulley with me, I'd do that. It has an extra belt groove.

Power Steering: I can't help with that. I think you are going to have a tough time fitting it all in. Philip, can you point us to the pics of the SD PS setup that you had?

My SD22 has a twin crank pulley. The forward/smaller diameter drives the A/C while the rear one drives the water pump and alternator.

I know of an '84 or '85 SD25 with A/C and P/S. I believe the crank pulley is a 3 groove affair. Same as SD22 but the second large pulley is for the P/S only. P/S pump layout.

View from underneath.


This is an SD25 with P/S and A/C.

[abumariah]

you guys really know your stuff...thanks for being so generous! al, i'd be thrilled with those brackets you mentioned. just tell me how to pay you and how much you want.

i reckon i will either need to find a wiring harness that can accomodate the accesories or fabricate one.

by the way, if there are any parts you guys want off that '81, you're welcome to them.

thanks again!

[asavage]

al, i'd be thrilled with those brackets you mentioned. just tell me how to pay you and how much you want.

I'll take some pics today.

i reckon i will either need to find a wiring harness that can accomodate the accesories or fabricate one.

I just sold the A/C-equipped wiring harness in November, to Andy in AZ whose harness was melted. I've since run into two people who also need A/C wiring harnesses. Since you've got an A/C-equipped '85, you'll only need a couple of wires for the compressor extended.

by the way, if there are any parts you guys want off that '81, you're welcome to them.

Keep the MF switch (turn sig switch assy). If you have keys that fit the Ign (or if your glovebox has the keycode on a sticker in it), pull the Ign. switch/lock assy. Even if you don't have a keycode, if you have a key that sorta works, I can "read" the key and make a new one. The Maxima and 720 Ign. assys. interchange, it seems.

On a swap, if your gasser's fuel tank is galvanized inside, the fuel tank should be swapped out for the diesel one. The sulfur in diesel fuel will combine with atmospheric water to form sulfuric acid that will eat the zinc in the galvanized coating and plug the fuel filter (if you're lucky).

Always pull the heater blower motor. It's easy to do, three screws and a cable.

[abumariah]

thanks for the info. I'm so pumped about working on all this stuff this weekend! i noticed in your pictures that the two sd's have a standard pancake air filter assem. mine has a canister mounted to the driver's fender. is the pancake a more efficient way to go?

[asavage]

The later SD25 ('83?-on) use the top-mount filter; our older ones have the can on the driver's fenderwell. The A/C steel duct on the top of the throttle body is flattened and has a horizontal bend in it, that the non-A/C version doesn't have. Hmmm. I guess I'm going to have to sell you that too.

Philip will insert a picture here of the A/C inlet duct. When I'm at work, I don't have the time to get fancy.

Abu: This is the air plenum Datsun supplied with factory a/c.





This is the standard air intake plenum for non a/c SD22. You'll also see this version with dealer/aftermarket a/c systems.