Hello again everybody, its your local hummer dumbass who drives purists insane.

By popular demand, and for reasons related to the solid axle swap, I will be attempting to Hydroboost swap my 2008 and get rid of that God-awful electric brake system from hell that has no business being in a road legal vehicle. I will give the details on why the solid axle swap requires this in my SAS thread as well as go over alternative solutions.

As for non SAS related reasons here they are...
1. No brake pedal feedback - Fine for daily driving, but makes left foot braking while traversing obstacles offroad damn near impossible. You can't feel the "bite" point of the pads.
2. Inconsistent braking performance - IMO dangerous even for street driving - Sometimes the pedal is soft, sometimes it's hard, sometimes it stops quicker than others. No rhyme or reason. I've replaced every part in the brake system, there are no leaks, it just is that way.
3. Digressive brake performance - The pedal progressively gets mushier after a fresh bleed of the system. Usually takes about a month or 2 of normal driving before its noticeably softer. After towing, aggressive driving, or offroading, it becomes unsafe. However a quick abs bleed with a scan tool restores it.
4. Parts availability - Apparently I bought the last brake unit in existence off of rock auto a couple years ago, sooooo good luck everyone else. These are non-rebuildable(Allegedly but I think it can be done).

I want to expand on #3 here for a moment. There is 100% without a doubt a defect inside every brake unit where air is getting trapped somewhere in the hydraulic cylinder the pedal is connected to. I suspect that this is due to cavitation of the brake fluid somewhere in the unit that's getting into the pedal cylinder.
In these units, the pedal cylinder is used for nothing more than a glorified pressure sensor. Its full of fluid and when you press down on the pedal, a valve releases some fluid back to the reservoir and a sensor reads the pressure. The EBCM reads sensor voltage, does some math, and sends a dependent pwm signal to the pressure valves for the calipers. Basically... caliper fluid pressure(for rear) and caliper fluid volume(for front) is dependent on pedal cylinder pressure.
When air gets in here, less pressure can be created, the sensor voltage is lower, and you are left with less braking power. I have felt and seen on the scan tool up to a 50% reduction in pedal cylinder pressure at full pedal travel after wheeling trips or towing.

Anyway... Here's the plan. First of all. I have no idea what I'm doing and have no idea if it will work. I'll take one for the team in terms of experimentation.

Since I want to keep this factoryish with no lights on the dash, I'll need to have an ebcm for the rest of the truck to communicate with that will have the same functionalities as the oem one. I need to find an abs pump/module compatible with hi-speed gmlan(2007.5-2010) and with the same options as my truck. If you look at a 2008 Cadillac Escalade, you will find it shares the same gm hi-speed lan and rpo codes as the 2008 hummer h2. JH6(Hydraulic power disk brakes) and JL4(Stabilitrak). I will try to use that one. I found a used(hopefully good) one on ebay for $50. I am going to buy that just to see if it's even possible to program it to my vin and make sure the other modules accept it and don't keep looking for an ebcm that isn't there anymore.



Fun fact... The EBCM is such an important part of the can network that the vehicle wont even start with it removed. There are 4 total hi-speed lan wires on the ebcm. Two going in an two going out. Downstream of the ebcm is the Fuel Pump Control Module, the Air Suspension Module, and the Terminating Resistor. If there is an issue with any of these wires the network goes down and the truck becomes a very large paperweight. Here's the totally legally acquired wiring diagram of the network so you can see what I'm talking about...

If anyone needs (totally legally acquired) wiring diagrams for 08/09 lmk. I have a few.
Oh and here's for the EBCM. You're welcome.


I have the pinout for the Cadillac EBCM as well on my computer at home. If this works I'll upload it here.

I will keep everyone updated on progress. Might be a week or two.

 

Thanks for posting,
very interested in this one,

Neal

 

Gavin, as always a new path blazer and if anyone could pull this off its you! Getting rid of that Toyota created ABS unit will be a crowning achievement.

 

Do you ever sleep? I bet your brain is going 24 hrs a day. lol

I admire your tenacity and your skills. Will be waiting to see the progress.

 

I do not sleep. There is nothing else I am good at in my life other than this type of bull****. But at least kind of f-ing around will probably land me a solid job out of college.

I also feed off of people telling me not to do stuff. I recently posted about my brake issue and possible solutions on the carhacking subreddit. I had a few people there tell me “buy the correct parts”(lol what parts?) “you shouldn’t be doing this” “it’ll never work” and my personal favorite… “you’re going to kill a family of 7 in a minivan.” No I’m not.


Everyone: “That’ll never work”
POV: me when it does…


Forgive my rant I’ve legitimately been awake since 6am… yesterday.

 

**********UPDATE**********
Hello again...

I have a very important update that everyone(especially me) will be very pleased about. I have confirmed that an abs pump and ebcm from a 2008 Cadillac Escalade(P/N 15834127) is a direct fit to the 2008 hummer h2. And by "direct fit" I mean not at all, BUT the electronics with little effort other than changing the connector. I didn't even have to program it, and all of the modules in the vehicle are happy. No codes from anywhere. Only codes I have are 6 codes all for sensors not being hooked up. It was as simple as matching colors. Minimum required was the two powers and grounds, 4 hi spd data lines, and the serial data enable wire. Here are the confirmed correct pinouts for each module. They are oriented looking at the front of the connector on the harness side. Be careful as orientation is quite confusing on these.



Thanks to the free charm.li website for somehow having the escalades diagrams that alldata didn't have.

One weird thing I ran into is the Escalade EBCM has a set of tan data wires and a set of yellow data wires while both pairs on the Hummer EBCM are tan pairs. The solid colors are can- and the striped are can+. I don't think it matters which pair connects to which pair as long as you don't cross the pairs and you connect + to + and - to -. Even though both pairs are tan/tan-black on the hummer side, they are still next to each other. The hummer side pairs are adjacent long-ways on the connector while the Escalade pairs are adjacent short-ways on the connector(vertical). Can stuff is pretty forgiving as long as you don't put 12v to it, its all 1 voltish, so if you screw it up, you probably wont break anything, it just wont work. The way you know it works is by testing resistance with a multimeter between can+ and can- on either pair. It should be 60ish ohms. If you did it wrong, it will say 120 ohms(only one side connected correctly), OL(multiple bad connections), or 0 ohms(just give up if it says this).

That was the big headache out of the way... Now I have to order parts: Master, booster, hydraulic hoses, and brake line.

Wish me luck!

 

That's great news, if you need any help finding anything post here and we'll lend a hand,

Keep us updated,

Neal

 

Wow… I’m still working on this but man has it been a headache. All stuff that can be fixed or better yet, would have been avoided if I knew then what I know now. Good news is anyone doing this in the future will not have to go through what I did as long as they read this.

I got lucky and found a hydroboost and master cylinder from an 08 Silverado on eBay for $75. I was then educated on the differences between 2010 and prior, 2011, and 2012+ hydroboosters.
Basically in 2011 there are some changes that make steering easier, braking more powerful and a larger accumulator. 2012+ is the same as 2011 but uses the symmetrical firewall mounting pattern from the vacuum boost trucks AND from 09/10 h2s. 2011 and prior have an offset stud for whatever reason gm thought that was cost effective.
I did later find a 2012 booster in a junkyard in nice shape for $45 but didn’t install it yet. If you’re looking for boosters. BUY THE 2012+. Makes life easier. No firewall drilling. Bonus points if you can get the hydroboost brake pedal with it. Also makes life easier.



I also purchased a generic hydroboost swap braided AN hose kit for $50 on eBay. This is fine. However you should NOT use the included rubber return hose, clamps, or the tee fitting. Get good quality oil rated hose.


After much fussing, I had to purchase a new power steering pump. You cannot tee together the power steering and hydroboost return lines. The small return fitting and internal filter on the pump create too much restriction and will blow your hoses off, soak your brand new belt, and leave you walking. Bite the bullet and buy a pump from a 2008 or equivalent Silverado 2500hd with the 6.0 that has two return fittings. Mine was only $80 at autozone and it works fantastic.

You’ll need some more things too and I’ll get to that.

I mounted my abs pump directly underneath the master cylinder. Motor side down, ports facing forward. That way I have to do minimal bending of the existing brake lines, and the new lines from the master are kept short. And yes. It will bleed and function just fine in this orientation. Just be sure to have the ports angled up slightly. Still working on the mounting bracket, but the lines are holding it up just fine.
Keep in mind the order of lines left to right is different. If you screw this up, stabilitrack will promptly put you in a ditch.


Wiring was straightforward. I know I posted 2 of the same diagram earlier. I will fix that later. Your can bus pairs on each are next to each other and twisted together. Wheel speed sensor signal and corresponding 5v ref are next to each other and twisted. There’s some color differences in either the yaw sensor or steering sensor I figured out by process of elimination. I mention this because the diagrams aren’t clear which 5v reference goes to which sensor. I don’t think it matters, but I played it safe and did it this way.


Everything does not work but will work later. I’ll explain. There are currently codes for 1. base brake pressure sensor(actually the sensor in the vacuum booster of the Escalade) and 2. the yaw sensor. 1. Can be fixed using a bypass mod I haven’t done yet but someone on the Escalade forum has. 2. Can be fixed by replacing the h2 yaw sensor with the Cadillac yaw sensor. Why they are different? Idk. That’s retarded. The wires are the same. I haven’t fixed this yet either, but this stuff WILL work when I’m done.
So anyway. You’ll need a pack of resistors(specified later) a relay, and an 08/09 Escalade yaw sensor.

now unplug your rear wheel speed sensors cuz this is where I get really angry and pissed.

CURRENT STATE OF THE TRUCK
I am driving this truck daily right now which is why I’m not working on it as much. Brakes feel AWESOME! Lights on the dash are not so awesome. I also have no working stability control, traction control, or abs, but internal proportioning of the abs pump is good enough that I feel comfortable driving it until I get the other daily fixed and a bunch of projects out of the garage and done.

All that being said, the axle swap and brakes have quite a bit of work to be perfect, but I LOVE the way this thing is riding and driving right now. I’m having a blast.


Back to the project
Why I unplugged the rear wheel speed sensors… one thing I overlooked was the # of teeth on the reluctor wheels. I figured that even if the tooth count was different, it was going to be symmetrically different on all 4 wheels between the Escalade and h2 and not be a problem(wouldn’t be true anyway). Because having different tooth counts between your vehicles on the same platform is crazy right? And it would be EVEN CRAZIER if they were not only different but staggered front to rear… RIGHT?!?!?!?

WELL… DO I HAVE NEWS FOR YOU!
The h2 comes with a 9.5 inch 14 bolt differential and 55 tooth tone rings on the rear axle and front wheel hubs. My new Dana 60 in the front uses the same 55 tooth rings. Nice.
unfortunately, the Escalade with the 8.8(awd) AND 9.5(2wd) used 32 tooth in the rear and 55 tooth in the front. Why? Idk. Probably just to **** me off.

Fortunately if you look online. Specifically at Yukon gear, they list a 32 tooth ring to go inside the axle housing for the 9.5 diff and specifically list compatible with Escalade, Silverado, sierra, and Hummer h2… okay cool. I’ll just grab a set of those. Just pull the axle shafts and it’s time for new bearings and seals anyway… **** THEY DONT FIT.


The h2 doesn’t use a ring/sensor in the tube like the 9.5s elsewhere. It has the ring on the end of the shafts, behind the hubs, and a sensor in the parking brake backing plate. Not only that but the tubes and shafts are different diameter, so I can’t just put it in and drill a hole.


I tried to cut off the old rings and cnc plasma cut some out of 1/4 steel, stack, and weld them on, but the plasma table simply isn’t precise enough. Went online to sendcutsend to have some milled, but they want $300/ea. BUT they have lasercutting(much cleaner than plasma) so I had them cut some out of 1/4 that I will stack and weld. Fingers crossed I find a way to get the airgap tight and consistent enough. This is what’s up next on the truck.




HOW YOU CAN AVOID ALL OF THIS
If I did more research and wanted to spend more money, I could have avoided a LOT of extra effort with sensor bypasses and tone rings

What I suggest for anyone doing this swap is to find an abs pump/module/connector from a 2008 or 2009(depending on your year) Silverado 2500hd with rpo JL4(very important). They are setup for hydroboost, so no sensor bypasses, and they work with the factory tone rings. The downside is they are $800-$1000 for a nice one(vs $50-100 for the Escalade) and getting hard to find. Sometimes you can get lucky and find someone who doesn’t know the difference in a jl4 vs jh7 pump(3 vs 4 outlets) and it’ll be $100.



The reason I’m going to continue the Escalade route is 1. I don’t have a grand to spend on another abs module
2. I don’t want to spend a grand if I have to replace it
3. Future parts availability(half the reason you’d want to swap)
4. I don’t want to reroute plumbing, and redo another 32 pin connector.

But for anyone else. Unless I figure out an easy tone ring solution, I would say just splurge on this one. It should have a bigger pump and internals and work better. I’m not sure I’m right about parts availability. I’ll have to dig further.

More updates coming soon. Not all details were included in this post but will be in the final write up.

 

Fascinating, really enjoy reading your thought process and amazing get er done attitude.

 

Gavin, I am absolutely amazed at your engineering and technical skills. You have taken on projects I am sure many GM specialty engineers would not have even thought of approaching.

I look forward to every update on this and all of your H2 projects. We here in the Hummer community are so lucky to have someone with your abilities and expertise in keeping these icon's healthy and on the road for years to come. Wow!