What to do next? Lots of questions!

So I have finally gotten some money that I can spend on my 06 h3 and make him more exciting. Right now it’s pretty stock. In the two years I’ve had it all I have done is raise torsion bars to level out, add k&n filter, and cleaned the drain lines because there was a ton of water getting in the car.

There is one thing that needs done and I’m not sure what to do. It says “SERV 4WD” on my dash. When I start the car I am able to cycle all through the 4hi and lo settings and activate neutral. But after a few minutes it stops functioning and I’m left in whatever drive it was last in. But I can restart It and get back to normal drive gear. I’m under the impression that it could be the selector switch but I’m just not sure. Any advice moving forward with that would be nice.

Now the fun stuff. I want to make tank (my kids named him TANK) more off-road capable because we enjoy it. So I’ll be adding new shoes and replacing the stock suspension. I’m not sure what tires I want though. I’m looking at the KO2s in a 315. But honestly I’m not set on that size or style. I want something is very capable off-road but still efficient on the road. So I’m not looking for mud grapplers or anything to knobby. Suspension I’m gonna go for the bilsteins 5100s.

I also want want to replace my stereo head unit, upgrade some sound on the inside, maybe replace the headlights with leds or add some halos the headlights. My wife saw one with red halos and she thought that was pretty cool.

I dont plan on overnight trips or extreme off-roading. Not going to Moab anytime soon I would love some insight from fellow owners

Best place to start with you srv 4wd error is a scan guage 2 or equivalent. Just went thru this with Miss' H and we replaced actuator, front hubs, rear speed sensors... In the end it turned out a trip to the dreaded stealer ship was the only way to find the issue ugh!
$700 dollars later it was repaired. ( Note: I dispize the dealer and for that matter paying to have others mess about in our Hummers) I usually do all the repairs possible. Alas I wasn't sure what was wrong and a tech2 was needed.

I'd get this issue sorted out first before fun stuff.

Things I Would Recommend:

Locking Diffs – The absolute best part to increase offroad capability.

Winch – You will get stuck. Having a winch will make it much easier and safer to get out.

Grille Guard/Bumper/Winch Plate – You need something to mount the winch

Schwarttzy’s Skid Plates – Protects your $1000 transfer case and $300 drive shaft.

Rocky Road Outfitter Sliders – Protects your body. Can stand on top of them. Adds Hi-Lift Jack point to side of H3.

Outfitter Design Tire Rods – The factory H3 tire rods are weak. You don’t want to break one of these out on the trail.

CB Radio – Stay in Contact with friends or other rigs out on the trail.

Seat Covers – Protects your leather or cloth seats from water, dust, mud. I recommend Coverking Cordura ballistic covers.

Daystar 1” Body Lift – Helps if you have rubbing issues with bigger tires.


Things I Would Avoid:
All of these things listed are what beginners do to their vehicles. None of this stuff improves the offroad ability of your rig or even utility for that matter. At one time I thought all of this was cool, but it is the furthest thing from it for anyone of has a decent amount of experience in the offroad world.

LED Bars
Smoked Taillights
Halo Leds
Tinted Marker lights, tail lights
KMC Rockstar Wheels or Moto Metals
Universal Roof Racks
Big Subwoofer Box
10,000K HID Headlights
Chrome Billet Accessories
Hoonigan Stickers
20inch+ Rims

Before you do anything crazy with the serv 4wd error, remove that trim panel, remove the button assembly and blow it out with compressed air. This fixed mine; it’s a very common issue especially if you ever wheel in dusty areas with your windows down.

I absolutely love my 35s; they are the single best offroading investment I have made. Aired down to 20psi I can go crazy fast on most terrain and I end up waiting a while for friends who are on smaller tires. I rarely use my lockers anymore unless the terrain is absolutely nuts. However, 35s will absolutely destroy your rig. Transmission, suspension, steering rack, CVs, front diff, etc. I’ve heard people achieve a happy medium on 34s, but IMHO you’re going to break stuff no matter what rig you wheel. So I would build up a rainy day breakage fund.

Acer4lo’s things to avoid list gave me a good laugh. Maybe add Monster stickers to that list.

Agreed on the dash buttons...try that first. The encoder motor is also an easy fix. If neither of these gets you going, then it’s most likely a worn shift fork and you’ll need to pull the t-case. Stored codes might reveal the problem.

On the mods...tires are definitely the most bang for the buck. Since you are only mildly wheeling, I would recommend the KO’s...great in rain, snow, and sand. They suck in mud but everything is a trade off. 315s may be a tad on the large side, and you can expect to loose some power and have some 3rd to 4th gear hunting. But a chip tune can help with that. If this is a concern stick with 285s.

Steering rack mount kit, differential mount kit, and winch/bumper are all very useful mods. A winch in particular can be a lifesaver...well worth the expense. At the very least, invest in a good tow strap and shackles. The KOs are not a pure off-road tire, so the extraction gear will be needed.

Skids, rails, lockers, and tie rods are also nice but, probably overkill for your intended use.

Yeah, lol we painstakingly cleaned the switch assembly and nope. The technician actually found a shorted harness and bad Borg Warner 24236866 tc345-110 module.
I chased that srv 4wd for a few years on and off and just couldn't find the culprit. There were no actual obtainable codes without a tech 2. I tried several expensive readers, scanners but no bueno.
The hubs were replaced as they failed within a year of each other. The rear speed sensors at recommendation of tech at her job and the actuator because it too failed about same time as hubs.

I just dread the stability, 4wd electrical Gremlins in this 06 H3 of hers. On the bright side I'm able to pretty much tell y'all where all the different items are lol!

Oh, before buying a bunch of bolt on cr@p just lightly wheel a few times and see what you feel is lacking. I can't tell ya the number of times people join the forum bolt a bunch of Doo dad's on and then sell because it doesn't live up to there expectations. Only you really know how your driving style works best for you.
Do you wheel?
Do you Mall crawl?
Do you weekend warrior?
Do you plow snow?
Clean or clear land, farm work, trees?

It's great to have a Hummer that looks good, great but pretty useless if it doesn't serve your needs.

Thanks for all the replies!

Ive been checking all the switches for the 4WD. I have gone all over the plugs too. I can get the switches to light up and activate. But nothing happens. Or so I thought. I had it in neutral with just the key in the on position. When I hit 4hi I can a ticking noise coming from the encoder Motor. I don’t have the time right now but I’m gonna try and and take off the motor and see what it’s doing. Input?

this is currently my daily driver and will be until about next fall/winter so I won’t be doing anything do drastic. Street > off-road.
I’m not to interested in a lot of bolt on do-dads. No led light bars or things like that. I will add crossbars to the top but currently my top to do is get my 4WD operating properly. depending on what needs done (ie: I can’t do it myself) I’ll get the 4WD fixed and new tires at the same time.

Actually found a replacement encoder Motor and I’m picking it up today. If it doesn’t fix it I’m allowed to return it. Pretty pumped. Worth the 45 minute drive. Hopefully it’s a bad Motor and this is the resolution.

You can switch modes without the encoder motor attached. This is sometimes useful if you get stranded. Simply remove the motor and rotate the stud with some channel-lock pliers. Keep in mind that this will not work if there is a shift fork issue inside the t-case.

ALWAYS chock the wheels when working on an H3 t-case or driveshafts! The vehicle can unexpectedly roll if you disconnect certain components.

PCM of NC Tune especially if you go with larger tires

Thanks for all the tips guys! I have classes all day so this evening I’m gonna remove the current encoder Motor and do my tests on it and the transfer case.

Has as anyone used the dorman 600-908 as a replacement before? I saw on one thread that power was backwards causing it to rotate in the wrong direction. Is this true? I can switch the pins or something if needed. Just trying to make plans before I hear things apart. I’ve been reaservhing the crap out it but I can’t find exactly what I need. Maybe I don’t know what I need.

How much do the pcm tunes cost? How long will the car be out of commission while that gets done?

1. Replace plastic shift fork with new metal one. Will have to get done eventually so better now while in your driveway than when on a trail.
2. 315 tires. Best upgrade for the $. The loss of power is barley noticeable and bigger tires are always better off road. Yes 33" will work but 35" is better.
3. PCM tune will get back the lost HP, reset the speedo & eliminate the dreaded PassLock.
4. Winch and all related recovery gear. If you always wheel with friends that have one then you can wait but never go it alone if you don't.
5. Steering rack clamp.
6. Replace worn suspension parts as needed.

Thanks. Good advice.
Whats passlock?

A buggy GM security feature (failure) tied to the key/ignition switch. PCM will intermittently not let your H3 start, requires you to wait 10 minutes before it will clear and let you start. Several ways to fix it, PCM way is free IF you are getting yours re-tuned by PCM of NC, a vendor here on the forum.

rascole said:

A buggy GM security feature (failure) tied to the key/ignition switch. PCM will intermittently not let your H3 start, requires you to wait 10 minutes before it will clear and let you start. Several ways to fix it, PCM way is free IF you are getting yours re-tuned by PCM of NC, a vendor here on the forum.

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Dang that would suck. Mine has gone into limp mode a few times. That’s super frustrating. But not that yet. *knocks on wood*

How come no one has 315s in stock of the KO2s! Wtf! Ugh. Was hoping to get the tires installed tomorrow but it’s looking like I’ll have to wait until November to get them. Time for google!

Not a fan of KO2’s because after a few trips out on the trails several treads were totally ripped off. Put on a new set of Nitto Trail Grapplers and did Poison Spider at Moab where at worst they were dusty afterwards.


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MilamJR said:

Not a fan of KO2’s because after a few trips out on the trails several treads were totally ripped off. Put on a new set of Nitto Trail Grapplers and did Poison Spider at Moab where at worst they were dusty afterwards.


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How were they on the road?

Fine. I thought that they would be loud but not much difference than the KO2’s.


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MilamJR said:

Fine. I thought that they would be loud but not much difference than the KO2’s.


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Awesome! Thanks. I like the look of those too. My buddy had a set of nittos and swore by them. He did a lot of off-roading.

Love my Duratrac 315s, I abuse the heck out of them and they keep taking it with minimal wear. I regularly do 45mph on rocky forest service roads at 20psi and quite a bit of rock crawling too. They are decently quiet for what they are, and definitely my favorite tire I have ever owned. Some people are concerned about the sidewall but I haven't had any issues even in situations with very sharp rocks. Yeah you can get dedicated mud or rock tires, but I also drive into the city a lot for work and they are great on pavement, rain, and snow too.

All 5 of my Duratrac 315s were only $1250 after tax installed, but that was over 2 years ago.

So I can’t find KO2s anywhere in 315/75/16. So far here’s what I’ve found. Input would be appreciated. I’m only shopping for 4 right now too. If something happens I’ll use the spare 285 like a donut. Eventually I will have 5 of the same.

Nitto Terra grapplers - 315/75/16 - $1020 with 30 day ride guarantee
cooper discoverer rtx - 305/70/16 - $736 with 30 day ride guarantee
cooper discoverer at3 xlt - 315/75/16 - $1104 comes with alignment and 60k mile warranty
Goodrich km3 - 315/75/16 - $1500ish - didn’t get a full quote but roughly 347 each.

obviously the cheaper one is more appealing but that’s almost a 2” tire height difference. I could get new rims too but that’s gonna eat most of my budget.

I have Terra Grapplers on my F250. Last about 50,000 miles and now on my second set. Liked them so well that is why I put the Trail Grapplers on my H2.


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