91’ suburban 6.0 ls swap

Jsynobie · Jun 20, 2020

I’m starting an 6.0 ls swap on my 1991 squarebody suburban looking for some advice. Over the next few weeks I’m swapping the engine, transmission And possibly transfer case out of a 2002 Chevy suburban and putting it all including all wiring dash gauges and steering column in my 1991 Chevy suburban. Has anyone completed all of this or some of it, That has advice for someone that is doing their first swap? Ripping things apart on both suburbans in the next few days. Can’t wait to feel the difference from the old 350 to 6.0 ls.

Crispy · Jun 20, 2020

You will probably want to find a way to bolt the 4L80E to the NP241 thats in the square. I believe the later model transfer cases drop on the opposite side of the earlier and even if they dont you would need to account for the electronic shifter on the newer unit.

I know the 241 bolts right up to a 4L60E but I believe the output shaft on the 4L80E is different. Sorry I'm not more help but its a point in the right direction.

yevgenievich · Jun 20, 2020

Put a ford front d60 in at the same time and the new transfer case will be pointing on the correct side for it

RoryH19 · Jun 20, 2020

See my k5 build in my sig. Have done all of this.

If you have a 91, you already have the initial fuel injection setup and the NP241c will have the electronic speedo.
You are off to a good start.

What trans does the donor have and what trans does the 91 have? This will help determine if they will bolt up to the NP241c.

Jsynobie · Jun 20, 2020

My transmission in my donor is 4l80e and the one in my 91’ is a 700r4. As for using the transfer case from my donor I have the whole vehicle to pick though for electronic shifter if I want but if the output is on the wrong side then maybe just stay with the original transfer case

bucket · Jun 20, 2020

You intend to swap in the entire dash, or just the cluster?

bucket · Jun 20, 2020

yevgenievich said:
Put a ford front d60 in at the same time and the new transfer case will be pointing on the correct side for it

This is a good idea.

I love manual shifters and "being 100% in control" but admittedly, I have really grown to like the pushbutton transfer case in my '00 Suburban. The Auto 4x4 feature works very well on roads with random snow drifts.

Jsynobie · Jun 20, 2020

bucket said:
You intend to swap in the entire dash, or just the cluster?

The whole dash lol just want to make things simple on the swap

bucket · Jun 21, 2020

Jsynobie said:
The whole dash lol just want to make things simple on the swap

Don't take this the wrong way but...

For the love of all things that are holy, please don't! Imho, the stock dash is nearly a work of art. For a modern truck, the '99-'06 dash is nice but it's the complete wrong size and style for an old truck. Making it fit will be one hell of a headache.

If you do go through with it, please give more attention to detail than the other folks have done when they give up on it and try to sell their half completed 'project' on craigslist.

Vbb199 · Jun 21, 2020

Can't remember numbers for sure, but I've been thru this already,
4L60e is I think 27 spline, same as a Chevy squarebody np208 and np241.

4l80e is 32 spline. Won't work with a square t case. Your options on that is, keep the newer suburbans transfer case, and run a "I think" 77-79 Ford d60 front like @yevgenievich mentioned. It'll be 31.5 Centerpin like a squarebody chevy.
But be mindful, usually one of those with no knuckles and no axle shafts and the seller will want 12-1500 for them.
They're direct swaps for alot of jeep people, so the price is wildly overinflated.

If you feel up to fab work optionally, a 87-91.5 kingpin Ford dana 60 could be used but it's 36.5 Centerpin and you may run into tire rubbing issues without spacers or the correct offset wheels.

My vote to keep it simple as far as 4x4 goes is a 4L60e and a squarebody np241 (90-91 burb, blazer and crew cab), it'll bolt right behind the 4l60e and has a VSS

But I'm with @bucket don't tear up the dash to retro fit the newer burb cluster in.

The 91 uses a super simple dash, positive and negative to feed each individual gauge, with a single signal wire to display the readings.

Only hurtle is the speedo, but you'll muscle thru that in the swap.
The 91 already uses VSS for speedo signal.

Vbb199 · Jun 21, 2020

Wasn't thinking in it, but I'm sure someone sells a output shaft swap kit for the 4l80e so you can go to 27 spline and use the np241, but I think you still run into the issue of needing an adapter to run the 91 suburbans t case.

Do a little looking around, you can find a 91 4x4 3/4 Ton I think gmc suburban, it'll have a 4L80e and a matching np241.
But those are REALLY hard to find.

yevgenievich · Jun 21, 2020

I just sold my 91 3/4 4x4 burb. Mostly regret selling it

Vbb199 · Jun 21, 2020

yevgenievich said:
I just sold my 91 3/4 4x4 burb. Mostly regret selling it

I would've gladly bought that piece off of you

Jsynobie · Jun 21, 2020

Vbb199 said:
Wasn't thinking in it, but I'm sure someone sells a output shaft swap kit for the 4l80e so you can go to 27 spline and use the np241, but I think you still run into the issue of needing an adapter to run the 91 suburbans t case.

Do a little looking around, you can find a 91 4x4 3/4 Ton I think gmc suburban, it'll have a 4L80e and a matching np241.
But those are REALLY hard to find.

I’m pulling stuff apart on Monday so I will start to see what is available and what I’m gonna use. I’m trying to do this swap with spending as little money as possible and in the three week timeline I gave myself. That’s my reasonFor doing some of the swap different than others

Jsynobie · Jun 21, 2020

Vbb199 said:
Can't remember numbers for sure, but I've been thru this already,
4L60e is I think 27 spline, same as a Chevy squarebody np208 and np241.

4l80e is 32 spline. Won't work with a square t case. Your options on that is, keep the newer suburbans transfer case, and run a "I think" 77-79 Ford d60 front like @yevgenievich mentioned. It'll be 31.5 Centerpin like a squarebody chevy.
But be mindful, usually one of those with no knuckles and no axle shafts and the seller will want 12-1500 for them.
They're direct swaps for alot of jeep people, so the price is wildly overinflated.

If you feel up to fab work optionally, a 87-91.5 kingpin Ford dana 60 could be used but it's 36.5 Centerpin and you may run into tire rubbing issues without spacers or the correct offset wheels.

My vote to keep it simple as far as 4x4 goes is a 4L60e and a squarebody np241 (90-91 burb, blazer and crew cab), it'll bolt right behind the 4l60e and has a VSS

But I'm with @bucket don't tear up the dash to retro fit the newer burb cluster in.

The 91 uses a super simple dash, positive and negative to feed each individual gauge, with a single signal wire to display the readings.

Only hurtle is the speedo, but you'll muscle thru that in the swap.
The 91 already uses VSS for speedo signal.

The reason why I’m doing full dash swap is to keep things as simple as possible. Not gonna tear up the stock dash at all just remove it. Thank you for the advice on transfer cases I’m gonna have to keep a look out for the best option and see what happens.

91’ suburban 6.0 ls swap

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