Hi PPL. I'm a new member coming over from Trailvoy.com yeah I'm an ex trailblazer owner which by the way is a lot like the H3.
Anyways I recently installed a Gear Vendors under/over drive for wheeling and was surprised to find that it can also increase mpg a lot.
Here's my setup
Manual Trans
Front leveling kit
Cold air tube
Cooper Tires DISCOVERER S/T 255/85R16
Gear Vendors underdrive/overdrive unit
PCM for Less Tune

My last three hwy trips I got 24 mpg not too shabby I can notice my gas gauge doesn't go down as fast in overdrive.
My next mod will be an HP tuners PCM so I can play around with the tune like I could with my trailblazer.
I'd also like to find a way to make my transfer case selectable, I was thinking a case from a Chevy Colorado might be able to be adapted, has anyone heard of this?

 

Your Trail Blazer taint no Hummer.....big misconception but glad to see you had it here with some possible alternatives.

 

I get so sick of people walking up to me in parking lots and gas stations trying to tell me I drive a Trail Blazer with a body kit.

 

Hahaha sorry man I didn't install this on my Trailblazer I install it on my 07 H3.

 

So with $4200 spent and 24 mpg how many miles do you have to drive to break even??

How much where the new drive shafts?

 

Or a Canyon/Colorado. I think the official number is that somewhere between 15-20% of parts are common and those are mostly engine/trans.

I come up with just over 90 tanks at CA prices to recoup the $4200 based on upping my mileage an average of 9 mpg. I fill up about once a week on average. So in my case it looks like the break even would be just shy of two years at current prices. If prices continue to rise it would be quicker. That's what I come up with unless my math is wrong somewhere. Not bad since it will continue to pay you back after that.

 

First I didn't buy the under/over drive for mpg gain I bought it cause it makes wheeling easier with a standard trans, but the mpg is there, mind you that city driving is the same mpg as before the install. Hwy driving is where I seen the gains when I could shift into over drive and get my rpms down.
I also pull at 4500lb camper trailer for work and pulling it in under drive and fifth gear seems a lot more stable than fourth in regular drive.
The kit cost me 3395 plus shipping and having the drive shafts redone and installed cost me just under 800 from my local 4x4 shop.
I didn't see much gains with my other mods which were done first, city drive is still maybe 15 to 16ish so this is no cure for this big azz suv.

 

:d lol