1976 with a 4.8 LS swap info

[Branktm]

I am getting gifted a 76 GMC Sierra Grande single cab short bed K15, came originally with a 350. Motor is gone, been sitting in a field for years. Also have option to take a 06 2wd silverado donor truck with a 4.8 Ls in it. I know its not the favorite ls swap, but its free and ive seen lots of info on getting good power out of it. Im new to forum so please point me in right direction if anyone has done this with a 4.8 before. The search engine on this forum wasnt much help, thanks!!

 

[hip2bsquare]

brandon, hi I am new to the forum... a few months. I am currently in the middle of doing a 4.8/4l60 swap in my '86 2wd swb truck. it is ALOT more involved then I had thought as far as the wiring goes.

 

[RoryH19]

x2
The swap takes time and typically more effort than most think.
Plus you have the added work of a transfer case and live front axle.
I've have done this swap with a 6.0/4l65e/np241 in my blazer.
Thread in my signature.
This covers the main points but definitely not everything.

 

[eskimomann209]

I am getting gifted a 76 GMC Sierra Grande single cab short bed K15, came originally with a 350. Motor is gone, been sitting in a field for years. Also have option to take a 06 2wd silverado donor truck with a 4.8 Ls in it. I know its not the favorite ls swap, but its free and ive seen lots of info on getting good power out of it. Im new to forum so please point me in right direction if anyone has done this with a 4.8 before. The search engine on this forum wasnt much help, thanks!!

There is virtually no difference between swapping in the 4.8 vs 5.3.
If wiring is kicking your ass buy a harness off the eBay. your 4.8 is fly by wire?

 

[Crispy]

You need to decide where you are going with the trans.

Are you planning on keeping the 76 a 4wd? If so, gonna use the existing trans and transfer case? They make adapters to bolt an old school trans to an LS motor.

You can also get a 4wd 4l60e and use an NP208 (wrong, its an NP241) to maintain stock 4wd shifter location. Most desirable NP241s are in the 90 and 91 trucks (maybe just 91, not 100% sure) because they have a VSS and will have direct input to the LS PCM.

The harness work is pretty tedious, especially if youve never done it before. I used this website (http://lt1swap.com/wiringharness.htm) and a couple of youtube vids. My project is on the back burner now but I got the harness stripped and am up to wiring the fuse block.

 

[Branktm]

You need to decide where you are going with the trans.

Are you planning on keeping the 76 a 4wd? If so, gonna use the existing trans and transfer case? They make adapters to bolt an old school trans to an LS motor.

You can also get a 4wd 4l60e and use an NP208 to maintain stock 4wd shifter location. Most desirable NP208s are in the 90 and 91 trucks (maybe just 91, not 100% sure) because they have a VSS and will have direct input to the LS PCM.

The harness work is pretty tedious, especially if youve never done it before. I used this website (http://lt1swap.com/wiringharness.htm) and a couple of youtube vids. My project is on the back burner now but I got the harness stripped and am up to wiring the fuse block.

Yes i plan on keeping it 4wd

 

[Branktm]

any experience with Easy EFI solutions on using their $700 wiring harness with the "three wire fire" conversion?

 

[eskimomann209]

You need to decide where you are going with the trans.

Are you planning on keeping the 76 a 4wd? If so, gonna use the existing trans and transfer case? They make adapters to bolt an old school trans to an LS motor.

You can also get a 4wd 4l60e and use an NP208 to maintain stock 4wd shifter location. Most desirable NP208s are in the 90 and 91 trucks (maybe just 91, not 100% sure) because they have a VSS and will have direct input to the LS PCM.

The harness work is pretty tedious, especially if youve never done it before. I used this website (http://lt1swap.com/wiringharness.htm) and a couple of youtube vids. My project is on the back burner now but I got the harness stripped and am up to wiring the fuse block.

241 not the 208.
90/91 is correct. Grab the instrument cluster as well to have a working speedometer.
To use other options like the 208 there are adapters that have a vss option and many signal conversion boxes available through companies like Dakota Digital.

 

[Crispy]

241 not the 208.
90/91 is correct. Grab the instrument cluster as well to have a working speedometer.

Thanks. I'm always getting that wrong.

If you get an older NP241 you can use a dakota digital pulse generator to give the PCM a VSS signal and maintain your existing cable driven speedometer.

 

[eskimomann209]

any experience with Easy EFI solutions on using their $700 wiring harness with the "three wire fire" conversion?

Does this include a controller for the 4l60?
Great thing about converting the ls harness is it controls the engine and trans and runs pretty efficient.

 

[eskimomann209]

Thanks. I'm always getting that wrong.

If you get an older NP241 you can use a dakota digital pulse generator to give the PCM a VSS signal and maintain your existing cable driven speedometer.

Yeah the 88/89 241. It has the mechanical speedo.

 

[RoryH19]

241 not the 208.
90/91 is correct. Grab the instrument cluster as well to have a working speedometer.
To use other options like the 208 there are adapters that have a vss option and many signal conversion boxes available through companies like Dakota Digital.

That's what I did, 90 NP241c and gauge cluster. Used all the stock drive shafts too.
Modified the harness myself, added dual electric fans and cruise control. Easier to add cruise with a DBW setup.

 

[Branktm]

I think i might back out of the LS idea... seems like the easiest thing is to just get a crate motor that bolts right in. No computers, etc to deal with. Plus probably close to same cost and have a new motor vs high miler LS

maybe im chickening out i dunno. Any other ideas or motors i should consider?

 

[Camar068]

There is virtually no difference between swapping in the 4.8 vs 5.3.
If wiring is kicking your ass buy a harness off the eBay. your 4.8 is fly by wire?

The harness isn't bad to do yourself if you have the patience and can deal out about 6-8 hours of your time. If not, ask around to see if someone in your area does them. If they do, they'll prolly throw in removing the VATS for you in the "bundle". Locally I've seen anywhere from $250-$300 for the wiring harness/VATS removal with you providing the harness.

 

[Shorty81]

Welcome Brandon, drop a good ole 350 in and go. It will bolt right in look natural in your truck.