Test Mule-Still Kick’n

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Captn. Crunch

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EE998C5C-8A23-4881-9FC8-EAA366A9098C.jpeg Hello
As you can tell from the photo, my build is a head scratcher to most so allow me to explain myself. First and foremost I can’t leave anything alone. Most everything I’ve ever driven has seen mods, some good some bad. Like my attempts at land speed racing on antique Harley Davidsons, I find myself drawn to improbable builds.
I bought this 99 GMC Safari AWD when my sons joined scouting and it became apparent so did I. Tried and True drivetrain with the torquey 4.3 Vortec engine, the venerable 4l60e automatic, the 7.625” rear end out of the camaro/firebird platform, the 7.25” IFS front diff from the S-10 4x4’s and the rest of the front end from the K1500 4x4. GM had the start of something fun, I just had to push a little bit.
First to go was the np136 one speed transfer case. It’s electronicly controlled to transfer torque to the front when wheel slip is detected. Upon further review, the np236 case from the S-10 was the same case with low range stuffed inside. I went so far as to buy two broken tc’s a136 and a 236 and built a case with parts from both to ensure that when I stated they were interchangeable I wasn’t talking figuratively but stating fact. With the addition of a dash switch and a dozen or so wires added to the existing harness I had 2hi 4hi 4lo and 4auto which is the same setting as my original AWD and it was a direct swap.
Next was to address the open/open diff situation. I needed something that would get power to both sides but not cause me hate and discontent on the street. I settled on a Torsen unit I found on eBay. It came out of a firebird and was a direct swap.
While researching the np236 swap I found the Zr2USA forum. They were instrumental in locating the tccm and wiring harness I needed. I quickly came to realize that these guys were seriously twisted and laser focused on offroad improvements on their rigs.
With so much being shared between our platforms I was quickly finding other items to swap into my van
One such item was a cast iron front differential found only in S-10 4x4’s with manual transmissions and the mp233 transfer case. I found one such unit from a properly equipped Zr2 to ensure it had the 3.73 gears found in all Zr2’s to match my vans 3.73’s. It was into this cast iron diff I had installed the at that time never before seen 7.2” Torsen carrier for a first of its kind cast iron limited slip. I swapped this unit in place of the stock aluminum open diff and upgraded both sideswith Detroit axles.
The S-10 pickup and my van shared the same length rear spring though the S10 was +5” in arc. I swapped in a set of S10 rear springs, lifted the front with a 3” body lift and a mild torsion bar crank. I increased tire size by 2” for a total of 6” of lift.
So I now have a van with twin torsens like an Audi Quattro, a two speed tc and underside armor from a Zr2 and a lift that puts the floor of my rig at mid thigh height. It handles like a dream and corners like a sports car. It has plowed thu three feet of snow yet I’d let my mom drive it. It really is a fun rig. I look forward to getting it well offroad to see just what it’s capable of-for I truly have no idea
 
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618s10

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That is awesome a bunch of good info on here can you post some pics of the build and after math of it
 

Captn. Crunch

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That is awesome a bunch of good info on here can you post some pics of the build and after math of it
I’d love to post up on this build but....
My ‘99 succumbed to terminal rot and had to be put down. I pick up an ‘03 Safari AWD to replace my beloved test mule. Full leather and a factory G-80 factory locker were bonus points. I have so far done the S-10 spring install, 2” body lift with a twist and swapped over the Torsen equipped cast iron front diff. Installed Falken Wild peak AT3’s. I’ve modified the rear shock hangers and getting ready to install the S-10 Blazer aluminum skid package. I’ll start taking pics as I go. I suck at that as I’m usually working by myself and just plain forget
 

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Captn. Crunch

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I had the van out in the snow a few days ago and I WILL be pulling the G-80 and swapping in the Detroit Tru trac. The twin Torsens handle perfectly in the snow, the G-80 was doing the locker thing and the ass end was all over the place. Thought I’d give it a try-I tried-it’s outa here
 

618s10

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So what's the difference between the two lockers
 

Captn. Crunch

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“The G80 used in GM brand trucks combines the clutch plates of a traditional Limited Slipdifferential with the positive engagement of the traditional mechanical locker. It does this by using a mechanical flyweight and a governor inside the differential, hence the "Gov Lok."Dec 21, 2004”
I grabbed that on line to save some typing time. The locker part doesn’t kick in til there’s a 100 rpm difference in rear wheel speeds. Then the centrifugal pawls open and lock the rear wheels together but only up to 25 mph. Then it disengages and once again becomes an LSD.
The helical gear unit or Torsen (which stands for torque sensing) is totally different. It constantly monitors the amount of torque being applied to each wheel and by design sends said torque to the wheel with the most traction. The amount of available torque is designed into the unit. The most common is the 2series which means the unit will divide the available torque in varying ratios from 50-50 up to 35-65. It will not exceed 2x the amount from one wheel to the other.
It’s all worm gears and math. No clutches to wear. No special additives required. No clunking, no grabbing, totally invisible.
With the twin Torsens I could mash the pedal to the floor and the van would accelerate perfectly straight. Power to all four wheels being adjusted constantly. Brake before the turn and hit the gas and power around the corner with the rear wheels following in the tracks of the front wheels. Neatest thing I’ve ever driven in the snow.
The only drawback is they multiply torque so if you lift a wheel off the ground, the other wheel will also have no torque being delivered. A light touch on the brake pedal will cause enough drag to trick it into thinking the wheel is back on the ground. Newer vehicles with ATC benefit greatly as the computer does the individual wheel braking automatically 1576108171932.png
 

618s10

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Sorry for all the questions and if some are dumb but I am trying to learn. So the g80 loses posi at 25 mph and is more like a lunch box locker or ratchet locker?? Did ether of these come in factory? If so what vehicles and years?
 

Captn. Crunch

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The G80 reverts back to a limited slip or better known as posi traction after the locker disengages after 25 mph. The lunchbox and the aussie ratchets are aftermarket with poor road manners. The G80 was and may still be a GM option in a huge number of their trucks and vans
 

618s10

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So your taking the g80 out and putting in the torsen right
 

JCWages

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The G80 reverts back to a limited slip or better known as posi traction after the locker disengages after 25 mph. The lunchbox and the aussie ratchets are aftermarket with poor road manners. The G80 was and may still be a GM option in a huge number of their trucks and vans
Aye, it is still widely used in GM trucks. In my experience it is loads better than a traditional limited slip in off-road situations but less useful than an electric or air locker. When in 4wd or Auto 4wd the locker is fairly seemless, espcially when flooring it in wet or snowy conditions. In 2wd there is definitely some clunking but it's still better than the old limited slip where a single tire on wet grass could halt all progress. lol There are better options for sure but I'll take the G80 over no locker.
 

618s10

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And also do they make any good posi setups for the front
 

Captn. Crunch

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There are a limited number of limited slip units for front diffsi had three options for my 7.2”. The “lunchbox” locker by Richmond I believe but they put too much strain on front end parts on pavement. There was also a place called Engineered Performance that built a friction style unit. I went with the Torsen style when I came across a bunch of Syclone/Typhoon owners collecting money for a limited production run of torsens for their 7.2’s.
I don’t know if there is any way to use a G80 in a front diff, but I don’t think it would be a good idea with its changing from lsd to locker and back. Not a great idea in a front diff if I were to guess.
 
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tjZ06

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Aye, it is still widely used in GM trucks. In my experience it is loads better than a traditional limited slip in off-road situations but less useful than an electric or air locker. When in 4wd or Auto 4wd the locker is fairly seemless, espcially when flooring it in wet or snowy conditions. In 2wd there is definitely some clunking but it's still better than the old limited slip where a single tire on wet grass could halt all progress. lol There are better options for sure but I'll take the G80 over no locker.
I have a G80 in my D'max and it's spent a lot of time towing trailers (and broken sand rails) in deep, soft sand. It works really, really well in those situations. It's also worked really well for light trail use with *mild* rocks. I suspect in more rocky or uneven terrain where one tire might leave the ground I'd see it's shortcomings.



Anyway, very cool van! Keep the updates and pics coming... and maybe consider some line-breaks in your posts to make them more readable. I'm honestly not trying to be a jerk, I did read your whole intro post because I found the build really interesting, but at least for my eyes it's a bit tough to parse.

-TJ