1998 350 to 454 Swap

[Mikeycook97]

So this is all still a little confusing to me but here it goes.

I got a 1998 Chevy 1500 4x4 from my work with a bad 350 in it. I believe it has a good 4L60E in it. Awesome interior, box looks like it has never been used. So I was looking for a new 350 but one of my friends told me they have a truck i could buy with a 454 so that's where this idea began.


The truck I bought for parts is a totalled out 2WD 1998 GMC 2500 with a 7.4L 454 BB(Big Block) connected to a 4L80E transmission, ending with a locking 4.10 2500 8 lug rear end.

Engine, I did some research already and so far, the computers in the engine bay are matching service numbers. Does this mean the harness is the same? Or can I get away with just re-routing/extending wires?

Transmission, for the 4L80E to work, what do I need to do? I know it's a 2WD tranny, I read I can have a tranny shop swap the tailshaft from the 4L60E to the 4L80E to make the tranfer case line up correctly, correct?
As for the crossmember being moved, can I take the crossmember from the 2500 and just swap it with the tranny to the 1500? Or will I have to fab some mounts?

Driveshaft, since the 4L80E is a little longer I need a shorter rear driveshaft and a longer front driveshaft. Basically I need driveshafts from a 98ish 1500 thats stock with a 4l80e right?

Suspension, I plan on swapping over all the suspension from the 2500 to the 1500.

Exhaust, I plan on swapping all the 454 exhaust to the 1500.

The transfer case and fuel pump should be fine from what I have researched.

Thank you for taking the time to read this, if anything I said is confusing, tell me. If I left anything out, tell me.

Both trucks are full not missing anything. The frame on the 2500 is not repairable.
I work at a recycling/scrap yard so getting used parts is easy for me. Any input helps!! Thanks in advance!

You must be registered for see images attach

You must be registered for see images attach

 

[Supercharged111]

2wd to 4wd conversion requires complete disassembly of trans. Engine harnesses are not the same, but the 454 harness ought to plug right in. It's going to require a flash too because of the transfer case that doesn't exist in the 2wd. I'd snag the engine and harness, wait for a trans and PCM to float along. Or just throw down to get it tuned, there's a TON of power locked up there. Your t case would require disassembly as well to play nice with the 4L80, or get a t case that was already sitting behind an 80.

 

[michael hurd]

The wiring for the transmission is slightly different, although you could make a 4l60 harness work, it's probably best to keep all of the wiring intact when you pull the 454 out. There are a number of swap guides on the internet for swapping a 4L80 in place of a 60.

The spline count is different in the transfer case. You can change the input shaft on your transfer case, or swap it out with one that originally came with a 4L80. ( easiest option if you have a yard handy )

For the crossmember, slide it back the required amount and drill 4 holes in the frame. As mentioned, the computer will not recognize 4LO range, it will not shift properly, but you can drive with it in 2wd mode, until you get it programmed.

The suspension will not swap, save for the rear leaf springs. The lower control arms are the same, but the uppers are different, and the mounting points are different. It's not feasible to swap the front differential and suspension over.

If your truck is a F44 chassis, and you have the 14 bolt semi-float axle, it is a decent unit, if you have the 10 bolt, it's a grenade waiting to happen.

 

[Supercharged111]

I don't recall if the trans harness is 1 with the engine but I think it is. the 60 harness is super easy to change over and already has your t case wiring present. O2 sensor locatons are different from 350 to 454. 350 has spider injection and 454 has injectors. 350 has 1 knock sensor 454 has 2. If you get a different t case, the front driveshaft length will be correct.

 

[Mikeycook97]

The wiring for the transmission is slightly different, although you could make a 4l60 harness work, it's probably best to keep all of the wiring intact when you pull the 454 out. There are a number of swap guides on the internet for swapping a 4L80 in place of a 60.

The spline count is different in the transfer case. You can change the input shaft on your transfer case, or swap it out with one that originally came with a 4L80. ( easiest option if you have a yard handy )

For the crossmember, slide it back the required amount and drill 4 holes in the frame. As mentioned, the computer will not recognize 4LO range, it will not shift properly, but you can drive with it in 2wd mode, until you get it programmed.

The suspension will not swap, save for the rear leaf springs. The lower control arms are the same, but the uppers are different, and the mounting points are different. It's not feasible to swap the front differential and suspension over.

If your truck is a F44 chassis, and you have the 14 bolt semi-float axle, it is a decent unit, if you have the 10 bolt, it's a grenade waiting to happen.

When you say I can make the 4l60 wiring work, does that mean splicing new wiring? how hard would it be to get the modules and wiring out of the 2500 truck and make them work in the 1500 so I don't have to reprogram.

 

[Mikeycook97]

I don't recall if the trans harness is 1 with the engine but I think it is. the 60 harness is super easy to change over and already has your t case wiring present. O2 sensor locatons are different from 350 to 454. 350 has spider injection and 454 has injectors. 350 has 1 knock sensor 454 has 2. If you get a different t case, the front driveshaft length will be correct.

Shouldn't be too hard to swap the engine harness am I right? Do I have to pull the dash out?

 

[Supercharged111]

I don't think so. I imagine harness is plug and play, but you may need one from a 454 4L80 4WD. Check yours and see if t-case is tied into engine harness and what the O2 sensors are tied into. 4L60 to 4L80 wiring is super easy, just repin the trans connector (no cutting or splicing) and add the front speed sensor and pin that guy into the PCM.

 

[Mikeycook97]

So I can't find any wiring diagrams for my transfer case wires. I want to see where they go and what they connect into? will the 98 2500 have the wires for a transfer case on that harness? even though it's not a 4x4 truck?

 

[Supercharged111]

You'll nees to get under the truck and see what's tied to what.