1994_3500_6.5 died, swaping in a 1996_3500_7.4...wiring questions...

[Another]

Project vehicle is a 1994, 3500 with a dead 6.5 but a good 4l80e. I have a donor truck 1996, 3500 with 7.4.. I will be putting the 7.4 were the diesel was sitting using the old 4l80e from the diesel. I have all the wiring from the 7.4. What is the best path for wiring it in so the dash works (tach), and transmission. 94 Transmission has the nss on column, and the 96 had it on transmission, how to fix that, what path or direction or site to find out were to start splicing or do I get a stand alone harness? Any advice/ help is appreciated.

 

[someotherguy]

To be 100% honest you have an uphill battle ahead of you. The '96 PCM isn't going to play well with that '94 transmission, to begin with.

Standalone harness for a Vortec 7.4?

You have a donor truck.. what's up with its transmission?

Richard

 

[GM Guy]

Project vehicle is a 1994, 3500 with a dead 6.5 but a good 4l80e. I have a donor truck 1996, 3500 with 7.4.. I will be putting the 7.4 were the diesel was sitting using the old 4l80e from the diesel. I have all the wiring from the 7.4. What is the best path for wiring it in so the dash works (tach), and transmission. 94 Transmission has the nss on column, and the 96 had it on transmission, how to fix that, what path or direction or site to find out were to start splicing or do I get a stand alone harness? Any advice/ help is appreciated.

IM a little biased, but id give the 6.5L a chance, sometimes you can sneak up on one for cheap. If not, you can swap some 6.5L components onto an old 6.2L for an economical replacement. 94 is a great year for them, quadstar multi-tuner is available for the 94-95 models.

 

[Another]

The 7.4_96 runs and drives so the transmission is good, its just that the warranty isn't even expired on the rebuilt 94 transmission. I'm guessing there is no stand alone harness for the 7.4? I thought I read you can get a holly cpu with a stand alone harness for the 7.4.
I'am not able to rebuild anything atm and got a price of 9g to fix the 6.5. I can however pull and swap.

 

[618 Syndicate]

@Supercharged111 has done this I believe.

 

[Supercharged111]

I did do that swap on a newer truck, but as far as I could tell it would have been the same on an older truck that started life as a diesel. As I recall it was plug and play to get the engine running, the C100 dash connector remained the same. I ended up making a jumper harness to get the dash working 100% (that was all behind the glove box). You'll need to jumper the speedo buffer too as the Vortec PCM will buffer the signal for you but it all flows through the firewall connections the same. If you want cruise to work, you'll need to swap in an interior dash harness and for the fuel pump, I grabbed that harness off of a donor. I also added the charcoal canister and line from that same donor. That's all I can think of off hand, see my build thread for more details.

CCLB dually #2

Hi, my name is Dustin and I have an addiction. Found this truck devoid of a powertrain. Originally a diesel, I intend to swap the powertrain from the parts truck into this and flip it. Interior is in good condition, body is pretty straight, no rust, but there is some clear coat peeling...

www.gmt400.com

 

[99xcss4]

I am in the same boat as you for the most part I agree with someotherguy it a lot of work. I started with 2 vehicles a 92 k2500 suburban that had a 94 power train swaped in to it and a very clean 94 c2500 pickup (8 lug) 6.5 turbo diesel cut the front ends out from under both and grafted the suburban front end to the pickup. pulled the whole drive train from the suburban and put it in the pickup and am still trying to get it running. I think your options would be get a stand alone controller for the 4l80e and a hei and carb swap or or you can go down the path I am trying to go down that is a tbi swap what is really bad you have an obd1 and an obd2

 

[Schurkey]

Don't forget to scrap the Diesel torque converter in favor of one with a stall speed appropriate for a 7.4L.

No doubt there's going to be significant exhaust mods, too.

Wire harnesses, computer programming, etc., I can't help with. I wouldn't even consider that swap. If they ever start doing emissions inspections, you're gonna be screwed.

 

[Another]

My thought on how to start now that I know a little more.
Take the entire wiring harness off the 96 front to back. Swap the 96 engine,transmission and the inner fenders so everything bolts up and looks factory. Get an aftermarket cluster and splice/solder the rest of the plugs and controls or just put in a 96 dash and column.

 

[Supercharged111]

Don't forget to scrap the Diesel torque converter in favor of one with a stall speed appropriate for a 7.4L.

No doubt there's going to be significant exhaust mods, too.

Wire harnesses, computer programming, etc., I can't help with. I wouldn't even consider that swap. If they ever start doing emissions inspections, you're gonna be screwed.

From what I understand there are 2 stall speeds: 350 which got the B82 high stall and B81 standard stall came with the 454 and 6.5.