2008 Suburban HD - 8.1L swap (frankenburban 2.0)

[jekquistk5]

You should have just bought a 8.1 Burb. Those where a plenty when I was searching for 3/4 burbs. It was hard to find a 6.0 burb, but the 8.1's were everywhere. I wanted a 3/4 burb before I decided to go new crew cab dmax. So you are in Watertucky(waterford)???

 

[fidelity101]

You should have just bought a 8.1 Burb. Those where a plenty when I was searching for 3/4 burbs. It was hard to find a 6.0 burb, but the 8.1's were everywhere. I wanted a 3/4 burb before I decided to go new crew cab dmax. So you are in Watertucky(waterford)???

I liked the newerbody style and interior and the GMT800s don't have stainless hardlines for fuel and brakes and etc. its the little things I like about the GMT900. I could not find an 8.1 burb without paying out the ass but it looks like that doesn't matter now lol. Yup waterford MI.

I am not spending 14k for a 12 year old GM truck. All of the 8.1 trucks I found were pretty beat up too. There was no middleground.

 

[fidelity101]

There may be hope yet! I have some friends at GM digging around for a possible bolt together solution. With a specific flexplate. Meanwhile, I mocked up the wireharness and I may only have to extend the evap solenoid and alternator wire. everything else pretty much fits where its supposed to.

 

[fidelity101]

Not a lot of feedback from the custom torque converter shops... but pursuing my parallel path of OEM parts, GM may have a solution for me it turns out...

Chevrolet Performance Transmission Adapter Kits 19154766:

Couple key comments -



Can I use the newer LS 4L60 Family electronic transmissions behind the older Small Blocks and Big Blocks?

As noted above, the bell housing pattern is essentially the same, but you will have the opposite converter nose to crankshaft pilot issue. (compared to LS engine to old style trans) The torque converter pilot on any LS style 4L60 family transmissions will bottom out in the crankshaft before the bell housing touches the block. In this case you need adapter kit p/n 19154766 to space the bell housing back approximately 9.6mm to gain the proper clearance between the converter and crankshaft when using the newer LS style 4/L60 family transmission behind a traditional small block.



Torque Converter to Flexplate Bolt Circle Diameter (BCD)

There are basically 3 different torque converter to flexplate bolt circle diameters (BCD) used by GM over the years.

The 4L80 family and TH400 use an 11.5” (292.1mm) BCD.

The early 4L60 (pre-LS engine), TH350, 700R4, 2004R, P/G, etc, use a 10.75” (273.05mm) BCD

Later “LS” style 4L60 family transmissions use an 11.062” (281.0mm) BCD. (6L80 is also 281mm)



Rear Crankshaft Flange Bolt Patterns

All early Chevrolet Small and Big Block with two piece rear main oil seals used the same 3.580” diameter 6-bolt flange pattern for attaching the flywheel or flexplate to the crankshaft. The Big Block has kept the same 3.580” 6-Bolt pattern regardless of the seal design (one piece or two piece) throughout its history.

In the mid 1980s the small block changed the rear main oil seal to a one piece design using a 3.000”

All Gen III and Gen IV LS design small blocks use a 3.110” (79 mm)





So it sounds like if I go with this kit and I re-drill my existing flexplate to match to the torque converter pattern and then this will work but the engine will sit 10mm forward in the truck so I may need to get a little creative in my engine mounts/mount brackets or move the trans brace backwards and take up some yoke slack.



It seems that if you have an LS you need dished flexplate to make up for the offset because of the shorter crank to maintain the bellhousing flange to crank flange gap. If you have an older style engine or BB with the long crank you need the flat flexplate to maintain that gap. Again this supports my theory that the the new LS engine family is just an SBC built with a computer instead of a drafting pad.

 

[NorCalAnthony]

Out of curiosity have you tried talking to some of the LSx specific torque converter places like Circle D or Yank? They make/machine a lot of their own parts and might be able to make something that other places can't or won't.

 

[fidelity101]

Out of curiosity have you tried talking to some of the LSx specific torque converter places like Circle D or Yank? They make/machine a lot of their own parts and might be able to make something that other places can't or won't.

I did, they were very helpful. Circle D said they could do a custom converter for 1200+ s/h and 2 weeks but they may only be able to get the stall down to 2500rpm because of the size of the torque converter 10.5" if I wanted to go with a custom flexplate they were suggesting that i needed to get the crank shortened 10mm for everything to line up. I do not want to pull the crank for something like this. I COULD go to a billet flexplate now I believe (with the gm performance spacer kit) but seems expensive for what I need.

Yank said it was feasible with their billet series as well but they lowest stall they could offer was 2800 - again due to size etc.

Pro Torque said they could make me a custom one where its the billet series using ultra low stall (similar to a diesel setup) and they could make the right pieces fit together for this to work so they asked me to fill out a custom torque converter form online and never heard back from them.

 

[NorCalAnthony]

Well crap. Hopefully you can figure something out that won't break the bank so you can keep the project rolling...

 

[fidelity101]

Well crap. Hopefully you can figure something out that won't break the bank so you can keep the project rolling...

Just got the kit in and its perfect... except the crank pattern is for the smaller SBC and the 8.1 is internally balanced so it doesn't need the external weight. I am going to try and re-drill the existing flexplate in conjunction with this kit and go from there. the kit provided has longer bolts for the bellhousing to engine but its meant for the gen I/II SBC which is standard thread, not end of the world I can just mcmastercarr some proper sized metric hardware.

Worst case I am thinking of getting a 1/16th" thick BB crank flange pattern made and just weld it to the small block flexplate to give it some girth in-case the re-drill looks like it has really ate away the meat on the flexplate.

 

[Truckman4life]

Why didn't you go with swapping in something like a 6.2L out of a denali or escalade? I think my wife's makes like 403 horse and 417 torque and has the 6 speed trans already. Big blocks are definitely more bad ass but I was just curious.

 

[fidelity101]

Why didn't you go with swapping in something like a 6.2L out of a denali or escalade? I think my wife's makes like 403 horse and 417 torque and has the 6 speed trans already. Big blocks are definitely more bad ass but I was just curious.

Those engines are about 4000-5000 at the junkyard before core/shipping/tax

 

[Truckman4life]

Those engines are about 4000-5000 at the junkyard before core/shipping/tax

Wow! Guess I better make sure to not let the wife ever blow the one up in her denali. At least you are laying the groundwork if I ever need to do an 8.1 swap.

 

[fidelity101]

Wow! Guess I better make sure to not let the wife ever blow the one up in her denali. At least you are laying the groundwork if I ever need to do an 8.1 swap.

yeah trust me, that thought crossed my mind. Also at the end of the day its still gonna be a small block which means its really wound out all the time for power.

I should have just bought a duramax quad cab and an enclosed trailer but I really like the SUV body for practicality and ease of reaching stuff like tools and spares during race weekends.

 

[Truckman4life]

This will be so much cooler than a duramax pickup too.

 

[fidelity101]

This will be so much cooler than a duramax pickup too.

I agree! That was the hardest thing to do when I was considering to sell my k5 burb, the cool factor is just too much. It didn't pick up chicks real well (I live in the city/burbs) but man I could pick up tons of old dudes if that was my thing...

you can apparently still order the suburban in a 3/4 ton in the new body style with the 8.1 or the 6.6 but its like 80k USD and special order for gov't use and etc, basically ready to be bulletproof'd. You can still order the excursion too... just in South America though...

 

[Truckman4life]

I agree! That was the hardest thing to do when I was considering to sell my k5 burb, the cool factor is just too much. It didn't pick up chicks real well (I live in the city/burbs) but man I could pick up tons of old dudes if that was my thing...

you can apparently still order the suburban in a 3/4 ton in the new body style with the 8.1 or the 6.6 but its like 80k USD and special order for gov't use and etc, basically ready to be bulletproof'd. You can still order the excursion too... just in South America though...

Stupid US emissions laws, we don't get any of the cool stuff any more.

 

[ZooMad75]

GM stopped putting 8.1s in light duty trucks in 2005. GMT800 bodystyle. They never got put in the GMT900's at all. Granted, GM was still building 8.1's up to 2009, but they were for Workhorse and Boat applications like Volvo/penta, Mercruiser and the like. There were probably some medium duty trucks that got them after 2005, but by then the General was in full Dirtymax mode pushing diesel.

Had they only seen the crap coming down the pipeline for emissions they would have probably kept the 8.1 rolling along much like ford has with the V10.

They were short sided enough with the plans of killing off the 8.1 for workhorse at least was to replace it with a supercharged version of the gen V smallblock. This discussion was being had back in 2008 solid couple of years before the first supercharged small block in the ZR1 vette was announced. While the blower certainly brings back some torque you still need to wind it out to get the power. I can only imagine a friggen 38ft gas class a motorhome with a 500hp blown small block. BZZZZZ ZZZZZZ

 

[Larry]

Very cool swap fidelity101!

Small world, Rob (Zoomad75) and I used to live out the Detroit area back in the late 90s/early 00’s. We’ll not live together, but our families live there when we went to work for GM out of college. We had a few work buddies that lived in Waterford. Rob lived in Royal Oak and I was in Rochester right downtown by the Paint Creek Tavern. Michigan was a great place to leave.

I dig the method of obtaining a 58x signal but that doesn’t work out for some reason PSI has a 58x reluctor wheel on their 8.8L that you could press on in place of 24x in the stock location at the rear of the crank shaft. The bad thing is that would require the crank to be pulled out to perform the pressing. The PSI part number is 80000564. The crank sensor to go along with it would be 8000562. I've researched this a little bit to go the other way by adding a 24x to an 8.8L to retain my harness and ECM in my K10 and Suburban if I ever get my hands on an 8.8L.

I also have an email into my contacts at PSI to see if they have a flexplate solution for you as I swore they had a 8.8L/6L90 combo running around in a test mule. One of the guys there seems to think there is a PRW flexplate that fits the 6L90 torque converter. Below are the 8.1L flex plates PRW claims to have. Might want to call them for measurements to see if any will work. A couple of them are drilled for different torque converter tab spaces.

PRW
1835021

1835030

1849600.. this one looks like the one you already have

Why didn't you go with swapping in something like a 6.2L out of a denali or escalade? I think my wife's makes like 403 horse and 417 torque and has the 6 speed trans already. Big blocks are definitely more bad ass but I was just curious.

Pfftt, look at the RPM range where the Torque and HP numbers start becoming significant. The 8.1L is making over 100 lbs. of torque at idle. Just because many of those LS engines advertise more HP and Torque on must pay attention to the RPM range where that power comes in. It is one thing to have high torque numbers in a hotrod but having them in the desirable low RPM range is much more important. High reving engines belong in sportscars not big tow rigs or off-roadsters but I am an old fashion kinda guy

you can apparently still order the suburban in a 3/4 ton in the new body style with the 8.1 or the 6.6 but its like 80k USD and special order for gov't use and etc, basically ready to be bulletproof'd. You can still order the excursion too... just in South America though...

Actually, no….the new uglyass K2XX Fleet Only 3500-HD Suburban is only available with an L96 6.0L. The 8.1L is long gone when Tonawanda stopped producing it in 2009 (although it stock was piled up to support Workhorse production through 2011) but its sole still lives on in the PSI 8.8L, which is currently only used for on-highway applications in my company’s IC Bus school buses on propane right now but we will offer it on gasoline next summer. It will appear in our medium trucks later.


Again, cool project. Subscribed

 

[fidelity101]

Thanks Larry! I've read pretty deeply throughout your 8.1 details, very helpful! I used to live in royal oak when I originally moved the area renting a place but now I got a nice garage and I like where I am just a bit north but I know exactly where you are talking about.

I'm really hoping I don't have to drop the crank. I build rotary engines - I always seem to put together overhead valve engines together poorly, I can't explain it... I had no idea there was PRW - thanks for reaching out to your friends at PSI.

I thought they didn't offer the K2xx suburban as a 3/4 ton, I thought they just built the GMT900 style just calling it a new model year and selling it as gov't spec. I think I saw one in NYC over the weekend with diplomat plates.

 

[fidelity101]

Called up PRW the two part numbers you have listed, only difference between the two is that one is lighter than the other (hence the holes) for quick launches. However the torque converter bolt pattern is different. they have 3 patterns the 11.5, 10.75 and some 9.XX" one

PRW suggested I needed 1834620 it is the 164 tooth ring gear not 168 but it does have an 11" pattern which can be made to work for the 11 & 1/16th but I'm not sure the guy understood what I meant. Thats what I hate about this swap I call places and people are confident in what they have but really don't understand what its going in so they provide the wrong part part #s

the description in it conflicts with the other details...

"Ford 429-460, 1966-97, Big Block, 164 Teeth, External Balance"

 

[Larry]

Thanks Larry! I've read pretty deeply throughout your 8.1 details, very helpful! I used to live in royal oak when I originally moved the area renting a place but now I got a nice garage and I like where I am just a bit north but I know exactly where you are talking about.

I'm really hoping I don't have to drop the crank. I build rotary engines - I always seem to put together overhead valve engines together poorly, I can't explain it... I had no idea there was PRW - thanks for reaching out to your friends at PSI.

I thought they didn't offer the K2xx suburban as a 3/4 ton, I thought they just built the GMT900 style just calling it a new model year and selling it as gov't spec. I think I saw one in NYC over the weekend with diplomat plates.

Well, that is a bummer. Was hoping they had one that would be a direct fit. It might be tempting to try their 1835021 and drill the holes you need. Surely, that would be less expensive than the GM 19154766 Kit.

Yeah, they offer a heavy version of the K2XX Suburban that just came out in 2017. Don’t feel bad, as most GM dealers don’t realize there is a HD Suburban either. Like the Chevrolet Caprice police cruiser, it is a fleet only vehicle available to municipalities and other government agencies. The powertrain is exactly the same as the GMT900 ¾’s with a L96 and 6L90 but with the hideous K2XX SUV body. For 2017 it was called Suburban 3500-HD but I noticed for 2018 they are just calling it Suburban HD. Still an ugly sumbish. To be honest, I am not a fan of the GMT900 trucks and SUV’s either. Those were the cheapest made and poorly assembled rigs in GM truck history IMHO. Although, I do like them better than the current K2XX SUVs by a long shot.

Well, good luck with your flexplate caper. If I come a cross any other info from PSI I'll let you know.
K2XX Burb HD with 8 lug wheels. Looks like a herse or Ford Flex on steroids Ugly submish and still doesn't have rocker panels below the doors just like the GMT900s