Swapping a z24 from a 84 4wd into a 2wd 85 sd25

[720boi]

Hey guys, im wondering what sort of modifications im going to need to do to the wiring(things like if im going to need to swap the harness from the 4wd), fuel lines, oilpan clearance from the 4wd oilpan, and if the motor mounts need modification im not very experienced with big projects and would appreciate any help.

 

Thanks

Paul :)  

[620slodat]

If I'm understanding your topic correctly you are planning on  pulling an SD25 out of the 1985 2wd and replacing that motor with  Z24 from a 1984 4wd. The wiring is slightly different between the diesel motor and the gas motor although I am not experienced with the wiring differences, but Wayno on this site is.

 

From experience I know that the motor mounts are not in the same location. The diesel motor mounts in the 85 will be about 1 1/2 inches (guessing) too far forward for the gas motor. The motor mounts (same configuration for the diesel and gasser) for the diesel will have to either be moved back, or an adapter plate made allowing the gas motor to be placed on the diesel mounts. I was in the process of putting an SD22 into a 1973 620 pickup when Wayno gave me a 1982 720 diesel frame. What I found was that the 1973 cab was a perfect fit (body mounts) onto the 1982 diesel frame.

 

With less work it may be possible to remove the 4wd suspension, the transfer case and and the front driveshaft from the 1984, put the 2wd suspension and driveshaft under the 4wd and never touch the motor mounts or the wiring and end up with what you want. I don't know what you ultimately want to end up with (2wd with a gasser motor?) or your abilities, but thinking out of the box could possibly require less work and money on your part.

 

Don 

Edited August 27, 2019 by 620slodat
spelling error

[wayno]

I think the only issue you will have is the engine mounts and the wiring harness, put the Z24 and transmission in and connect the transmission mount, now make a set of mounts for the engine motor mounts to connect to.

You will need to use the Z24 wiring harness also, the diesel harness doesn't have the wiring to power the coils, the diesel wiring is not user friendly for a gas application, I tried finding a keyed power source for the VE type injection pump in my inline injection pump truck and the best I could do was use the window washer power source with a relay to make the starter work, it was a pain.

By the way, that SD25 engine and transmission is worth something, people want them engines because they have more power than an SD22 and they bolt right in.

[720boi]

Well i suppose i should have specified what the big plan was. Im taking the z24 out of my 4wd because its a rust bucket and i would never be able to fix it and register it. So i found a 85 with a blown sd25 that was already taken out of it and stripped apart because of a cracked head, and when i went and looked at the truck i saw that the frame was completely rust free and would be a sweet project that i could try and it was only $300 so i snagged it and brought it home. So I need to put the z24 into the diesel.

 

When i finally get my manuals if the mail ill begin taking the z24 out and measure the mounts 

 

thanks don!

 

Paul :)

[wayno]

I just thought of a couple of other things that might be an issue, your going to need a 2wd oil pan and oil pick up tube for that Z24 engine, I believe the 4wd engine sits higher in the frame and I don't think the 4wd oil pan will clear the 2wd cross member.

Also your 4wd likely has a short shaft transmission, I don't know what 2wd chassis/frame you bought(kingcab, regular cab long box, regular cab short box), your likely going to need the proper drive line, what is the 2wd frame/chassis?

Edited August 27, 2019 by wayno

[720boi]

Its a king cab

[720boi]

and wouldent the trans off the diesel bolt on to the z24? or are they different?

[wayno]

Kingcab 2wd 720 trucks all have long shaft transmissions, your 4wd transmission is likely a short shaft so you will need to find a 2wd kingcab drive line, early 4wd trucks have a long shaft transmission, but around 1983 and up 4wd trucks all had short shafts.

You could take the front case off the diesel transmission and put the Z24 front case onto it from your 4wd transmission and then sell the front diesel case for quite a bit of money to someone, diesel guys need that case and so do the Roadster guys as the R16 and U20 Roadster engines use the same transmission bolt pattern as the diesel engines and the Roadster guys like the overdrive gearing in the 82/83? Z cars and it will mount on their engines with the diesel case.

[720boi]

Do you mean Swapping the bell housings on the transmissions? I have the driveline from the 2wd, actually the transmission is being held in the truck with a ratchet strap currently so I was wondering if I could just mate that one with the z24 without any swapping?

Edited August 27, 2019 by 720boi

[datzenmike]

Biggest difference between diesel and gas transmissions is the starters are on the opposite sides.

[wayno]

Yes, but it is more than just the bellhousing, it's the front half of the transmission, and your lucky as the both of your transmissions likely have the large lower counter shaft bearing.

Here is a link on how to take off and put back on the front case.

 

[datzenmike]

Well '85 was the year the 62mm counter bearing was introduced. I had an '85 diesel transmission and it was the larger one. Just pull the 62mm counter bearing off the diesel transmission and get a new 56mm bearing from any pre '85 transmission and hammer onto the diesel transmission so the Z series case will fit. To fully drive it home use a suitable pipe that just fits over the counter shaft and bears against the inner bearing race.

 

If for some reason the transmissions are the same length you could take the rear case off the diesel that has the speedometer drive pinion and swap the worm gear off the main shaft to the Z24 transmission main shaft. It's held on with two C clips and very easy to do.

[igotatruck]

What you gonna do with those 4wd parts?