Build Hummer H3 Build

Skinny said:

I think the computer has a table for the low range ratio that it is multiplying by when it sees the input that the tcase is in low range.

Maybe that value is wrong for whatever reason. But I think you'll only get it to work correctly with a single low range ratio.

I am by no means a 6L80 or tuning expert. I just remember seeing those values somewhere in my PCM tables. I too bought an HP Tuner because of poor calibration done by so called professionals.

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The more I think about it the more I think the tcm is setup off of a Denali and I believe those were awd (only 1:1) and not 4wd

Skinny said:

I think the computer has a table for the low range ratio that it is multiplying by when it sees the input that the tcase is in low range.

Maybe that value is wrong for whatever reason. But I think you'll only get it to work correctly with a single low range ratio.

I am by no means a 6L80 or tuning expert. I just remember seeing those values somewhere in my PCM tables. I too bought an HP Tuner because of poor calibration done by so called

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The 4l80e read off the tcase tail housing, the 6l80e reads off the transmission tail housing. So the stock speedo is reading 5.4x's the actual speed when in low low. The only way to really correct it is to somehow read the speedo off the tcase tail housing, while still sending transmission tail housing speed to the tcu.

06h3 said:

The more I think about it the more I think the tcm is setup off of a Denali and I believe those were awd (only 1:1) and not 4wd

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Good point, the escalade is that way also. Tcase looks a lot like a 241 or whatever, but was insanely light with no low range and magnesium housing, had nothing connected to it at all.

Is the transmission function fine and it's really just about making the speedometer read correctly?

Skinny said:

Is the transmission function fine and it's really just about making the speedometer read correctly?

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It works perfectly fine, just speedo is off in low range

While I still have a few things to iron out on the 6l80 swap like the speedo being off in low range. I have decided I can work on that little stuff after the baby is here. That doesn't require as much time as linking the rear.

So Coilover's are ordered. 12in 2.5 Fox Coilovers, DSC's. Accutune told me the spring rate they picked is 350/400. I am 225/350 in the front, and I am about 50/50 weight bias when loaded for a trail like the rubicon. The rear coilovers will have more angle on them to lessen the rate but I gave them my accurate rear weight (sprung and unsprung) and said add a little more weight because it is not uncommon for this thing to end up carrying peoples crap on the trail or being the tow rig for broken down rigs.

With that said, I have decided on a triangulated 4 link. I think it is just the right way to do it for strength and numbers. I can do the 3 link and achieve the anti-squat I want but not the roll axis and lose strength with 1 upper link. I can do a 5 link (4link with panhard) and get the strength, but I can't get the anti-squat or roll axis numbers I want. So, 4 link it is. My one requirement is no fuel inside!

I know of 1 triangulated 4 link H3 and he used a TJ Genright tank. I am not spending 1600 bucks on a fuel tank.

So here we go...



TJ and ZJ tank. We will see which one fits better. 19 gallon and 23 gallon and go behind the rear axle.



Since I don't always run a spare anymore I will be cutting all this crap out, it hangs out far and in front of it is a lot of 1/8in plating from the factory that housed factory sway bar mounts, factory muffler, evap stuff, shock mounts, etc. That will allow me to move the gas tank up as high as I possibly can.

I will cap the frame and do rec. tubing between the frame rails for a gas tank mount, hitch receiver, and tow points. I will have the hitch receiver mounted low enough for times that I do run a spare I can use a hitch extension to protect the tire.

My hope is that I can fit a ZJ tank in there. its 23 gallons and the factory H3 tank is 23 gallons. I am confident the 19-gallon TJ tank will fit as a backup if the ZJ tank doesnt work out. From the other H3 guy that used the genright tank he said that the height of a TJ tank is the same as an H3 and the fuel gauge reads accurately. I will be remounting the evap crap I remove and mounting it along the frame rail. As always, keeping it operating like factory is important.

I am equally excited and nervous about this mod. The leafs have kicked ass for years but I think they have run their course and by the time I price out nice shocks, new leafs (not factory but from deaver/alcan,etc.) a new anti wrap bar setup I am getting close to linking it money. I hope this is an overall win.

Goal is to have it done before the baby shows up and be driving the baby home from the hospital in the hummer.

Here is a random picture, unfortunately a friend of mine passed away in a tragic event last Saturday (standing in the pic.) A group of us are adding pictures to a google drive folder for a slideshow and someone posted this. This is probably back in 2009. It's cool to see the Hummer still trekking along and how many memories it has provided with friends. It's been in the family for 18 years and has been in my life for more than half of my life now.

I believe I still have an XJ tank if you need to test another.

Oh and a YJ tank as well.

Thank you Lincoln !!!

Let me do some research and I’ll let you know. The YJ tank is 15 gallons right? XJ is 19 or 20?

06h3 said:

Thank you Lincoln !!!

Let me do some research and I’ll let you know. The YJ tank is 15 gallons right? XJ is 19 or 20?

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The XJ is out of my 89. The YJ is a plastic 94. I think they are both 19.

I gave the XJ tank to a friend to test in a waggy. Pretty sure its still there. Maybe that is where the YJ tank is.

Things escalated quickly yesterday lol there’s plenty more metal I cut out since that pic. Anyways, cut out all the old crap. Mocked up the TJ tank. I don’t like how low it sits. It’s about 25.5 to the lowest point before a skid is there. I was about 32 to the lowest point before. It still sits higher than the stock fuel tank currently but it definitely hurts departure angle. I knew I’d lose clearance but hoped it wouldn’t be that much. There’s a nice lip I could cut out in the body to give me and extra inch or two. There’s also dead space that’s being wasted. It’s to be expected when using a random off the shelf tank. I need to ponder my next steps. This may be a 2 step process. Build the 4 link, throw a tank in for the time being and then come back and do a tank. I like Brennans approach. I don’t have Brennans skills. I am confident I could take the foam board and make the shape but would have to farm out the actual cutting, bending, and welding of the tank.

If you want it to operate like stock, depth of tank is pretty important so you can run a factory pump, correct?

Can you sacrifice come cargo space to get it higher?

NORDFORD said:

If you want it to operate like stock, depth of tank is pretty important so you can run a factory pump, correct?

Can you sacrifice come cargo space to get it higher?

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Yes, factory depth is needed to run a stock pump and the TJ and H3 have the same depth. With that said, having a pump more towards the rear axle would allow me to taper the end for departure angle.

I’d really like to leave the cargo area alone but I’m open to any and all suggestions. Here’s why I wanna leave it alone.

Have you looked at the F150 tank? It's much shallower, but no idea if it's the right shape.

Trail Quest modified one of their tanks for me back in the day. It doesn't look like they make them anymore but it may be worth a call. The YJ tank I had made was 12ga with a 12ga skid. I had them make their 23gal to 15 and modify the pickup.

Look at BJ Off roads waggy tank. I think it is too long but warth a look. A friend put in one in with his 5.3 conversion. If I remember correctly he modified a pickup from something else. Didn't seem like a big deal.

The XJ tank is tapered and the pickup is at the front. Stick an ohm meter on yours, I wouldn't be surprised if range is the same.

06h3 said:

Yes, factory depth is needed to run a stock pump and the TJ and H3 have the same depth.

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Do you want to run the stock pump for the fuel gauge or just to make the wiring and fuel line situation easier?

I know the GM computers can be scaled for different sized tanks if you're concerned about the dash function

YotaAtieToo said:

Have you looked at the F150 tank? It's much shallower, but no idea if it's the right shape.

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I haven’t, what year?

Lincoln said:

Trail Quest modified one of their tanks for me back in the day. It doesn't look like they make them anymore but it may be worth a call. The YJ tank I had made was 12ga with a 12ga skid. I had them make their 23gal to 15 and modify the pickup.

Look at BJ Off roads waggy tank. I think it is too long but warth a look. A friend put in one in with his 5.3 conversion. If I remember correctly he modified a pickup from something else. Didn't seem like a big deal.

The XJ tank is tapered and the pickup is at the front. Stick an ohm meter on yours, I wouldn't be surprised if range is the same.

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I’ll look into it.

fl0w3n said:

Do you want to run the stock pump for the fuel gauge or just to make the wiring and fuel line situation easier?

I know the GM computers can be scaled for different sized tanks if you're concerned about the dash function

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I just know it works and don’t want to mess with it, every person I know who has messed with non factory fuel pumps on their engine spend all this time ****ing around fuel pressure issues. Maybe it’s my friends not sizing them properly but it just seems to be an issue.

Here’s an update. Axle is out. All the crap behind the rear axle is all cut out.



Nice leaf spring bushing



I thought I was gonna tear up a little. Those leaf springs have put in work for 18 years. Thank you for your time, now you can rest easy in retirement on my sideyard

Fresh housing

So I’m out of town the next 3 weekends. I won’t be able to work on it again until the weeknights of Oct 16th. My buddy is flying out the weekend of Nov. 4th and that’s the time to really get this **** done.

We have been talking about a game plan. I will continue to research more tanks and options and we are reconsidering the 3 link. Like I mentioned, I can get the same anti squat numbers I need. Roll axis is a little worse but a sway bar can help with that. Then gusset, gusset and more gussets, and tie in to as many things as possible

It's the rear tank for an 80-90s F series truck that usually came with 2 tanks

I'm with you on the factory fuel pump, just mounted a toyota pump in a fuel cell for that reason. Although it wouldn't be hard to change the depth if you had to.

Zero gravity does a lot of tuning also. Those folks know their ****.

06h3 does your tune know when the TC is in low range?

gt1guy said:

Zero gravity does a lot of tuning also. Those folks know their ****.

06h3 does your tune know when the TC is in low range?

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It gets the signal but nothing changes that’s why I think it’s a base tune from an awd vehicle with no low range.

Zero gravity did another h3 and he said his speedo is way off too.

My guess is I’ll change the base tune to a vin that I know has 4wd

YotaAtieToo said:

What do you think about starting a 6l80e thread in gen4x4?

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06h3 said:

I’d be open to it. I have a video on how to program starting in any gear

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A thread would be fantastic. Hopefully I'll have a rig with a 6l90 running in the not too distant future........hopefully.

Skinny said:

I think the computer has a table for the low range ratio that it is multiplying by when it sees the input that the tcase is in low range.

Maybe that value is wrong for whatever reason. But I think you'll only get it to work correctly with a single low range ratio.

I am by no means a 6L80 or tuning expert. I just remember seeing those values somewhere in my PCM tables. I too bought an HP Tuner because of poor calibration done by so called professionals.

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In HP Tuners you'll have pages that look like this....under transmission.

I'm very slowly trying to learn how this stuff works, or at least make sense of it .









My understanding is that it's the OS and VIN# that determines what options are available to use. Not 100% sure but, I think all the 6l80/90's are physically capable of all the functions. So a trans in a Camaro could have a tow/haul mode and adjust for a low range, but those tables are not in the software for the Camaro.


Anyway, I vote make a thread

Does anyone know if the vehicles these came in had wheel sensors? I'd think most newer stuff will, and possibly just read the speedo off those?

Yeah I understand about 1% of what my HP Tuner is capable of. I use it more for making **** work in a powertrain swap then to actually tune anything.

So from what I understand the "segment" is the programming your computer comes with for that spec of vehicle. It's the same controller just different configurations and data in the tables. So yeah you could segment swap a Camaro trans with a Silverado and it's the same hardware but completely different calibrations.

I know for a fact that GM gives you a table for the low range ratio and an input to tell it when to use that number. But trying to make that work for various low range ratios is beyond my skillset unfortunately.🤣

YotaAtieToo said:

Does anyone know if the vehicles these came in had wheel sensors? I'd think most newer stuff will, and possibly just read the speedo off those?

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Anything that has ABS will have wheel speed sensors.

gt1guy said:

Anything that has ABS will have wheel speed sensors.

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Well you're probably right 90% of the time, I know ford trucks had just a rear ring gear sensor for years and had rear abs starting in the 90s.

Either way, do the 6l80e rigs use wheel sensors for speedos?

YotaAtieToo said:

Well you're probably right 90% of the time, I know ford trucks had just a rear ring gear sensor for years and had rear abs starting in the 90s.

Either way, do the 6l80e rigs use wheel sensors for speedos?

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Not sure. This is the deep end of the pool for me........and I sink.

gt1guy said:

Not sure. This is the deep end of the pool for me........and I sink.

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There is an option on HPtuners where it asks what will it read from and wheel speed sensor is an option. I’ll screen shot it today

Ok, so the wheel speed sensor signal can get to the speedo. I believe it gets there through the canbus.

The path that it takes is what gets my head spinning. Because the BCM is what sends the signal to the speedometer in the dash.

I just looked at the tune I'll be starting out with when I get my pile running. It confirms what you showed. Though it's from a LS swap in a JK.




For my use I need have it setup to read the signal from the VSS on the HERO tailshaft. I don't have any wheel sensors.
I'll forget to do that, so when you see me start a thread about why my speedo doesn't work...........just remind me please.

While I mentioned in my last update post I was out of town for the next few weeks I have been contemplating things in my head. Has anyone ever built a steel fuel tank before? I see that there are a few companies that sell an anti rust paint that is for fuel tanks. Damn near every tank up until the 90s was steel until plastic tanks became a thing.

The reason I ask if any of you ever have is that it doesn't seem as common. The reasons I like steel is that it is something myself and/or friends can build at home. It is tougher than aluminum. I fear that a few good hits (even with a skid) the aluminum will crack upon impact. Steel should dent vs. crack. Since I can build it and design it, I can maximize the space for the most gallons vs using an off the shelf aluminum or plastic OE tank which range is important to me.

I am thinking I either build my own tank or I 3 link it at this point. To maximize tank volume I need a tank 37-39in wide and less then 16 in long because it will hit the rear diff. I plugged those parameters in the dorman search function for tanks and nothing good came up.

I haven't seen a rust problem with my dads tank but we do everything we can not to run ethanol. They do make a coating for tanks that are rusting. I would think that would be a good prevention measure.

I do know one, maybe a couple, that do coast guard certified tanks out of aluminum.

My dads tank has two braces in it that run front to back. The pickup sits in a little cup that is welded to the bottom of the tank. It has some holes on the bottom of the cup that I assume lets gas in and controls the slosh. The cup is formed, it really looks bought.