Another 1991 Suburban

[sean257]

I ordered it off of ebay. right at 100k miles. Something automatic for transmission, suggestions welcome. Looking at craigslist for 4L80e right now.

I was wondering if the windows might be a kit of some sort with all of the screws, and the way things overlap in a home made kind of way

 

[PMA4x4]

Are you still planning on doing the gear change anyways or are you going to wait and see what the new powerplant does?

 

[sean257]

Are you still planning on doing the gear change anyways or are you going to wait and see what the new powerplant does?

Going to stay with the 4.56, and use 37" tires. It looks like if I use a 4L80e with a .75 vs the .7 of the 700r4, I may need to go the other way on gears instead?

 

[PMA4x4]

Going to stay with the 4.56, and use 37" tires. It looks like if I use a 4L80e with a .75 vs the .7 of the 700r4, I may need to go the other way on gears instead?

I think you are starting to split hairs but I have been known to do that myself....quite often in fact. Math on that .05 difference does show 150rpms lower. Its possible.

I plan on doing the same (going from 3.42s to 4.56s) and getting to where you are but my math will have me just a couple hundred rpms above stock as I will be using 255/85-16s. I currently am running 33x10.50s.

if you are wanting to know the extra weight you have added I had plan on weighing mine. I figure since mine is still close to stock and all I have added is the roof rack and bumpers which I know the weights of that would tell us the bone stock weight of these trucks. +/-100lbs maybe.

 

[Renntag]

Awesome build. The bumper and roof basket fab are awesome.
I am preparing to do the same to a 91 burb repowered with a 6BT retaining the 4L80E that was driven by the 6.2 diesel that came from the factory.
I am somewhat concerned about weight and considering aluminum for the roof basket, but cost will weigh heavily in my decision as well.

Sadly I have the tailgate and annoying electric rear glass. I'd love to have a flip up glass option. That would be an interesting fab project.
The barn doors make for a nice ladder mount. I will have to get creative possibly with a side mounted ladder or a pull out and flip down onto the bumper.

Your Burb is sweet. Thanks for sharing the details.

 

[redthies]

I am somewhat concerned about weight and considering aluminum for the roof basket, but cost will weigh heavily in my decision as well.

Don't worry! I just built a headache rack for my 3500, and the difference in price between steel and aluminum tubing was 5%. I obviously went aluminum. The only extra expense was paying a friend to tig it for me, as I only have a spool gun for aluminum.

 

[sean257]

I would have went with aluminum, but the guy that built it did not have what he needed to weld aluminum.

Last picture before heading off for more work.


ARB Locker and Yukon ring gear

 

[sean257]

It looks like an Allison 1000 is just going to be more $ than I need to spend for capacity than I really do not need, so I am looking for a 4L80e. I would like to stay with an auto.

 

[PMA4x4]

Where is it off to for more work and what for?

Nice locker!

 

[sean257]

Off to my trusty mechanic/fabricator's house, as I do not have that ability. Getting the locker, 8.1, transmission, trimming and fender flares so I can fit 37's, ???.
We will still need plenty of advice, as he has never done this particular swap before.

I am very interested in the weight when you get yours to the scale.

 

[PMA4x4]

I'll let you know on the weight as soon as I get it done. As for advice on the 8.1, flares and tranny I think you're going to need Larry for that.

 

[sean257]

Awesome build. The bumper and roof basket fab are awesome.
I am preparing to do the same to a 91 burb repowered with a 6BT retaining the 4L80E that was driven by the 6.2 diesel that came from the factory.
I am somewhat concerned about weight and considering aluminum for the roof basket, but cost will weigh heavily in my decision as well.

Sadly I have the tailgate and annoying electric rear glass. I'd love to have a flip up glass option. That would be an interesting fab project.
The barn doors make for a nice ladder mount. I will have to get creative possibly with a side mounted ladder or a pull out and flip down onto the bumper.

Your Burb is sweet. Thanks for sharing the details.

Thank you. That will be an awesome setup you will have. I think a side ladder would be pretty cool, the way I drive between trees though, I'd probably tear it off.

 

[sean257]

Larry, would you mind telling me some details about your exhaust? Tube size, mufflers. I am guessing you do not have cats?

 

[Larry]

Larry, would you mind telling me some details about your exhaust? Tube size, mufflers. I am guessing you do not have cats?

Sure thing….

The ‘78 K10 w/ 2002 L18 8.1L:
Stock exhaust manifolds, dual 2.5” pipe from tip to tail with a cross pipe behind the cab and dual Thrush Welded Mufflers (these are basically Flowmaster knockoff's but not as obnoxious as a Flowmaster). No cats used. The firing order was changed from 1-8-4-3-6-5-7-2 to 1-8-7-2-6-5-4-3 on the Gen III small blocks (LS) and the 8.1L. With the change in firing order the exhaust sounds really odd when running true duals. A cross pipe (H-pipe) is badly needed to equalize the LH and RH banks and prevent them from sounding like two poorly tuned 4 bangers fighting each other. Or use a single inlet/dual outlet muffler to help equalize the banks. There are some sound clips in this 8.1L specific thread.

Once the 2005 8.1L gets into my '89 Polar Bear Suburban I may run it exactly the way it is now with the TBI 5.7L where it has a Y-pipe from the manifolds, large intermediate pipe that leads into a single inlet/dual outlet Flowmaster with 2.5” pipe from the muffler to the exit just for the sake of saving space underneath the Burb for goodies that may be added later. Running true dual exhaust eats up a lot of space that could be used for extra fuel storage or water tanks under the Burb. I don't run a cat on the Burb either (no emissions testing where I live )

 

[sean257]

Sure thing….

The ‘78 K10 w/ 2002 L18 8.1L:
Stock exhaust manifolds, dual 2.5” pipe from tip to tail with a cross pipe behind the cab and dual Thrush Welded Mufflers (these are basically Flowmaster knockoff's but not as obnoxious as a Flowmaster). No cats used. The firing order was changed from 1-8-4-3-6-5-7-2 to 1-8-7-2-6-5-4-3 on the Gen III small blocks (LS) and the 8.1L. With the change in firing order the exhaust sounds really odd when running true duals. A cross pipe (H-pipe) is badly needed to equalize the LH and RH banks and prevent them from sounding like two poorly tuned 4 bangers fighting each other. Or use a single inlet/dual outlet muffler to help equalize the banks. There are some sound clips in this 8.1L specific thread.

Once the 2005 8.1L gets into my '89 Polar Bear Suburban I may run it exactly the way it is now with the TBI 5.7L where it has a Y-pipe from the manifolds, large intermediate pipe that leads into a single inlet/dual outlet Flowmaster with 2.5” pipe from the muffler to the exit just for the sake of saving space underneath the Burb for goodies that may be added later. Running true dual exhaust eats up a lot of space that could be used for extra fuel storage or water tanks under the Burb. I don't run a cat on the Burb either (no emissions testing where I live )

Thank you sir. Mine is registered in the Peoples Republic or Illinois, so no emission testing for vehicles older than 1996. I think I will stick with dual, but I would not have known to add an H or an X pipe.