1999 GMC Jimmy "AT4"

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Forte

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Alright it's time for a build thread for the little Jimmy. I'm calling this thing the Jimmy "AT4" after the off road package on the newer GMCs although this one is probably more capable... Come join me for the ride with this less than common rig as I outfit it to explore the deserts of Arizona with my family!

How it sits today:
PXL_20201117_213624219~3.jpg

First, a little background. I've had this thing for about 8 years now, purchased after the engine in my Taurus SHO became oiling challenged. After years as a reliable daily driver and with winter coming, I needed to get rid of my dry rotted tires that were getting scary in the Nebraska ice and snow. After finding a 2" body lift on Craiglist ($50 new in box!) I knew it was time to step up in tire size.

Before pic:
IMG_20180706_063045_083.jpg

Decided on 31x10.50r15 Goodyear Wrangler Authorities (they're like budget Duratracs!). 31s are the factory tire size on the ZR2 off road package which means no excessive stress on the drivetrain; reliability is the goal on both a daily/overland rig.

IMG_20200430_210312_067.jpg

Installing the Performance Accessories body lift was pretty straightforward, didn't need to extend the fuel filter neck or mess with the steering shaft. I did run into one speedbump as my factory bumper brackets were integrated to the factory trailer hitch. Angle grinder took care of the factory tabs, and the lift brackets bolted on top of what was left. Bumper also got a nice treatment with the angle grinder to eliminate interference with the frame, and the lift was complete!

Buttoning up on the lift with middle helper:
IMG_20200730_184209.jpg

Bumper bracket details:
IMG_20200803_121905.jpg

Bumper trim:
IMG_20200803_140258.jpg

And finished! Oldest helper says "these tires are huge!":
IMG_20200802_161923.jpg

In June I lost my job with the railroad due to COVID-19 related slowdowns, so we packed up from Nebraska and moved back to our hometown of Fountain Hills Arizona. The Arizona heat did a number on our older vehicles including the Jimmy, and I gathered parts for an electric fan swap. I found a very clean Chrysler Concord in the junkyard with a dual speed, dual fan setup ripe for the picking. This fan is interesting as it has built in relays to control high and low speed operation. When either positive lead is given 12v, both fans turn on low. If both leads have power, both fans run on high. So far under normal driving the fans are typically keeping the truck at 200 degrees on low speed only controlled from a temperature switch. High speed will be wired up in the future as the truck does get warmer on long climbs in the mountains on 95+ degree days.

My highly technical wiring diagram:
IMG_20201008_211700.jpg

Finished harness:
IMG_20201013_161615.jpg

Harness installed in the engine bay. I removed the windshield washer tank to fit my relay/fuse setup as my lines have long ago disintegrated and were worthless. Most of the wiring is hidden under the airbox which is removed in this picture:
IMG_20201014_221335.jpg


Oldest helper grounding the wire to test fan operation:
PXL_20201017_172121570.jpg

Fan with aluminum bracketry:
PXL_20201018_225151893.jpg

Electric fans installed!:
PXL_20201018_171719139.jpg

Next step for me was comms. I've had a Cobra 19 CB radio circa 1989 in and out of the Jimmy since I bought it, and a buddy had a 4' Firestick laying around so with that we had a plan. Custom bracket was cut from 1/8" steel plate and bolted above the tail light. 18" coax ran through a grommet behind the tail light and into the cabin. Tested SWR at 2.2 at channel 1, 1.4 at channel 19, and 1.2 at channel 40 which I figured was good enough out of the box.

Coax routing:
PXL_20201115_040654674.jpg

And we have comms!:
PXL_20201115_185420124.jpg

At this point @bawesomfels asks me if I want to hit up Broken Arrow trail in Sedona AZ in a couple of days for a shakedown (more like torture test) of my rig. I had a few things to take care of prior to hitting the trail. I knew the front plastic bumper cover was going to be an issue, so I swapped my nice bumper out with an older steel inner bumper I had laying around. Unfortunately My 31s had also been rubbing on the front fenders if the suspension traveled up while the wheels were turned. Equal parts angle grinder and BFH took care of that problem ( these less than perfect edges will be covered up by plastic cladding, but I don't think the cuts look too bad for using an angle grinder...) It was about then I realized that due to the body lift, my remote oil filter was now glaringly exposed between the bumper and front skid plate. A solution was found that is definitely "function over form".

Radius drawn out in Sharpie:
PXL_20201116_213754600.jpg

This is by far the most redneck picture of the thread so far:
PXL_20201116_222949011.jpg

And the final product!:
PXL_20201116_234326715.jpg

Wife and I ended up hitting the trail without the kiddos this time. It was her bday weekend, so we spent the day in Sedona AZ and drove to Jerome AZ to spend the night in the haunted Jerome Grand Hotel. The Jimmy did excellent on the trail, stayed 200 degrees the whole time and for the most part kept up with Ben's Frontier. Smacked the frame pretty good a couple of times and dragged the trailer hitch a bit. I'm glad we didn't bring the kids as the trail was a long rough ride that would have likely gotten old for them after 15 minutes... Going to start them off a little more mellow than that.

And now you're all caught up!

Big and middle helpers are ready to explore! (littlest helper isn't in many pics as she just turned one and is more of a watcher than a helper for now):
PXL_20201102_004817787.jpg

Future:
I have been collecting a ton of parts for this thing so I will be tinkering with it as time allows. Next mods include:
-Skid plates: The front skid on the truck is part of a set of four Kevlar composite plates. Definitely going to want the other three installed prior to another trail like Broken Arrow.
-Front bumper: I have an old winch plate sitting around that I will likely be fabbing up for a front bumper for the truck. I am currently teaching myself to weld so fun projects are always in the works.
-Lights: I picked up a box of assorted 6" halogen lights on Craigslist and ordered a pair of H11 led bulbs to toy around with. Thinking A pillar lights.... I also have the factory HID headlights that are in my "before" pic that need new bulbs and the lenses refinished, they will eventually be swapped back on.
-Envoy center console and spoiler: My brother picked me up a Jimmy Envoy center console which has a cd changer built in. My radio is going to be relocated to this center console which will leave my factory radio slot available for auxiliary switches and a phone mount. I also have an Envoy spoiler which just looks plain cool!
-Sliders: Another fab project I'd like to take on.

Thank you for reading, happy explorations everyone!
 

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reaver

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Nice man. I owned a 96 blazer and I loved it for the 16 years I drove that thing. It finally died with about 280k on the clock.

Out of curiosity, which drive train do you have? Is it part time 4x4, or do you have the AWD option that some of them had (that may have been limited to the bravada, but I'm not sure).

Those Kevlar skids are hard to find, so good luck with that. I also know Rancho makes a 6" lift for these rigs, if you're interested.

Following this build, as I have a soft spot for the 2nd gen S series rigs. :blush:
 

Forte

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Nice man. I owned a 96 blazer and I loved it for the 16 years I drove that thing. It finally died with about 280k on the clock.

Out of curiosity, which drive train do you have? Is it part time 4x4, or do you have the AWD option that some of them had (that may have been limited to the bravada, but I'm not sure).

Those Kevlar skids are hard to find, so good luck with that. I also know Rancho makes a 6" lift for these rigs, if you're interested.

Following this build, as I have a soft spot for the 2nd gen S series rigs. :blush:
Thank you! I'm at 176k and don't see any quit in her yet.

I definitely forgot to mention drivetrain details. It's a stock 4.3l vortec and 4l60e automatic transmission through the "four button" np236 transfer case. This is the 2hi, 4hi, 4lo, and 4 auto option which actually worked amazing in the snow and I used it all the time. Stock 3.42 gearing and no LSD.

I deleted the front axle disconnect using a one piece center shaft from a Bravada. You are correct those are all time awd. This mod replaced the unreliable vaccum actuated and weak disconnect.

I was lucky to find the full skid plate set on a truck that was being parted out! I've seen a lot of three piece sets but not many four piece sets as those only came on four door Blazers and Jimmys. It's front skid (installed), engine skid, transfer case skid, and fuel tank skid (the rare one).
 

reaver

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Nice! I had the standard 3 button transfer case in mine. I never had an issue with it, but that was before I really got into off road stuff.

You could look into sourcing a rear end out of a zr2 s10. They came with the g80 auto locker, which works surprisingly well (I have one in my Colorado, and it works great). I'm not 100% sure what the gearing is on the zr2 though. You might also look into swapping the front diff from a manual s10. They're cast iron iirc, and MUCH stronger than the aluminum ones that came in the blazers.
 

Forte

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Nice! I had the standard 3 button transfer case in mine. I never had an issue with it, but that was before I really got into off road stuff.

You could look into sourcing a rear end out of a zr2 s10. They came with the g80 auto locker, which works surprisingly well (I have one in my Colorado, and it works great). I'm not 100% sure what the gearing is on the zr2 though. You might also look into swapping the front diff from a manual s10. They're cast iron iirc, and MUCH stronger than the aluminum ones that came in the blazers.
Yeah I think if I stay IFS the iron front diff and rear G80 would be a good option, it seems that a lot of Zs came with 3.73s which also makes the swap pretty nice. Of course the other option is a solid axle swap.Turns out you can run stock hubs on an XJ Dana 30 and run stock wheels and ABS... Pretty neat. Or I might even sell the Jimmy and build out my Expedition lol. The future is wide open!
 

reaver

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Don't sell the Jimmy! There aren't enough overland S series rugs out there. By the way, I've got a brand new fan Shroud sitting in my shed somewhere, if you ever want one. Just pay for shipping and it's yours.
 

bawesomfels

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At this point @bawesomfels asks me if I want to hit up Broken Arrow trail in Sedona AZ in a couple of days for a shakedown (more like torture test) of my rig.
I can't wait to get back out and really start testing your rig, especially once you get some more done! Broken Arrow was such a blast.
 

diabetiktaco

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Yeah I think if I stay IFS the iron front diff and rear G80 would be a good option, it seems that a lot of Zs came with 3.73s which also makes the swap pretty nice. Of course the other option is a solid axle swap.Turns out you can run stock hubs on an XJ Dana 30 and run stock wheels and ABS... Pretty neat. Or I might even sell the Jimmy and build out my Expedition lol. The future is wide open!
You'd have to swap the entire diff. The ZR2's were 8.6 ring gear. The Jimmy is a 7.5.
 

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Very awesome.
 

Forte

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Last few months has been pretty Maintenance heavy for the whole fleet.... Trying to get our Expedition to pass emissions, fixing wiring in my wife's Mazda (rats got in the engine bay), and confirmed a rear main seal leak on the Jimmy.... The trans will eventually come out to fix that (and likely get a shift kit and a tcase rebuild in the meantime) but in the meantime I'll just keep it topped off on oil...

Did get some time to get a few fun things done on the Jimmy!

First grinded, smoothed, and painted the CB radio antenna mount. Added some nylon washers under the bolts to tighten things up too. Looks professional!
PXL_20210331_174453230.jpg

Next moved my Superstrut crossbars and rooftop box from the Expedition to the Jimmy, pictured with the traction board mounts. Thread here on the Superstrut: Superstrut crossbars for budget rooftop box

After I got the crossbars located where I wanted them I removed the topper box and stored the traction boards. When I load up for camping the box will drop right on and bolt down with four bolts. Next step will be to purchase a set of Quickfists for the driver side to mount a shovel.
PXL_20210328_210225728.MP(1) - Copy.jpg

Then lastly, one of the best $60 investments I've ever purchased. Added a Rough Country steering stabilizer. It fits OK, the shock is a little long so it bottoms out just before I hit full lock on the steering in a left turn... Still the ride improvement is worth it. The truck has always had a tendency to follow ruts in the road and the 31s have magnified this. Hitting a bump mid turn would almost jerk the steering wheel from my hands, and now the steering is not affected at all. Little wins!
PXL_20210410_042213044~3.jpg
 

Forte

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Well it's been over a year and l've gotten only a few things done with the Jimmy... But more importantly got my life sorted out a bit. Bought a house, got a new job that isn't 24/7 on call, and (most importantly to this build) bought a new daily driver. The Jimmy has officially been upgraded from daily driver to weekend toy! Also with the new job l'm hoping to have more time to wrench and more time to take the family camping.

I finally got the 2 door spare tire carrier mounted, and had a buddy who upgraded his YJ from 31s to 33s so he gave me his spare tire. The Jimmy also hit a huge milestone. Sept 2022 marked ten years I've owned the truck.

Finally it was time to renew my registration so I went for a custom plate. Officially AT4 Jimmy! At the same time I cut back my exhaust pipe about a foot and installed this tip I had laying around. Attached are the most recent relevant pics. Recently hit a mild trail with the family and @bawesomfels in his new Ranger Tremor to get out of the house and enjoy this beautiful AZ weather.

Hoping to get some minor suspension stuff sorted with the rig so I can spend a little more time outdoors before it hits 100 again here... Also now toying with the idea of a solid axle swap. Garage needs a little more clearing then I'll be able to get the Jimmy in and start sorting out plans...

Cheers all!
 

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DintDobbs

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@Forte She's a looker! I dig the 2nd-gen S trucks. It's too bad they weren't as common as the Explorers. The 4.3 put out an impressive amount of torque!

I'd be wary of body lifts though; the bumper brackets aren't some thing I would ever put on my trucks. It somewhat weakens the structure, and the leverage would be positioned from a different angle in the event of a collision.
 

reaver

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Yeah, I bought a 96 Blazer in 2004, and drove it until about 5 years ago. I still miss that thing. It finally died with 274k on it.

I like where you're heading with the build.
 

Forte

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@Forte She's a looker! I dig the 2nd-gen S trucks. It's too bad they weren't as common as the Explorers. The 4.3 put out an impressive amount of torque!

I'd be wary of body lifts though; the bumper brackets aren't some thing I would ever put on my trucks. It somewhat weakens the structure, and the leverage would be positioned from a different angle in the event of a collision.
Thanks! Yeah this 4.3 has been super reliable and very torquey. I almost bought a first gen Explorer before I bought this, better off road chops and 33s with minor lift.... but besides the engine the promise of easy troubleshooting of OBD2 was too tempting. Prior car was OBD1 and I spent too many hours counting CEL flashes and emissions was always difficult, it's super strict here in Maricopa county.

Body lift was a calculated risk. Truck has an OEM tow bar in the rear that was unmodified by the lift and there are also front and rear crossmembers capping the ends of the frame rails, but of course all of us who modify vehicles have to accept early that anything non-factory means the vehicle will not behave exactly as the engineers designed it. It'll be even less factory when I finally get around to the winch bumper in front. :laughing:

Yeah, I bought a 96 Blazer in 2004, and drove it until about 5 years ago. I still miss that thing. It finally died with 274k on it.

I like where you're heading with the build.
My brother has an 04 Sonoma with 215k on it, I'm looking forward to hitting the 200k club soon. Thanks!
 
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Forte

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Quick update, finally found my shovel mount brackets I had lost in the move. Threw them on with a new shovel, and bolted a section of unistrut on the tire carrier in order to mount my traction boards in preparation for an overnight trip in the mountains. Truck looked good and the china trasharoo worked great with a tall kitchen trash can in it!

Not driving the truck much other than around town these days, steering is getting pretty sloppy. It's looking like I need ANOTHER idler arm, which is a common issue on these trucks especially with bigger tires... Looking into a one ton idler arm swap, bit pricey for an idler arm but it's the next step to "bulletproofing" the IFS on this truck. Not ready to drop about $250 on that just yet.

Vital IFS mods on the S series trucks for reference if anyone is curious:
Oldsmobile Bravada one-piece front axle shaft (eliminates the weak vacuum axle disconnect) - done
Proforge HD tie rods - done
Steering stabilizer - done
One ton idler arm
Diff drop helps as well but you can only drop it about an inch before you interfere with the steering linkage

Most people just solid axle swap by this point... haha
 

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Forte

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IT'S MAINTENANCE TIME
Drove the old girl to my dad's shop with the goal to fix the MANY oil leaks that this truck has and tear apart the transfer case to investigate a marbles-in-a-can noise I have when in 2wd.

Truck is getting:
-Timing cover and gasket
-High volume oil pump
-Oil pan gasket
-Rear main seal
-Oil sending unit
-Remote oil filter lines
-Engine mounts
-Transmission mount

Also inspecting rod bearings and looking into an overheating issue, thinking I might have a plugged radiator as my lower rad hose seems to be collapsing under higher load, higher RPM. Truck stays cool as can be around town and on two lane highway but pulling up a hill or accel/decel through traffic it will heat up. Cools right down as soon as I get the RPMs back down...

Super excited to get all of this done, it's been basically ten years in the making LOL. I can't wait to enjoy this truck more, leak free.
 

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reaver

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I'd be shocked if there was a mid-90's GM vehicle that DIDN'T have oil leaks! Good on you for keeping her on the road though. I've got a soft spot for these things.

Also, I totally just realized you had a lift gate! So neat that these could be had with both a lift gate, and a tail gate. I personally had the tail gate in mine, and used it as a chair all the time.
 

Forte

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I'd be shocked if there was a mid-90's GM vehicle that DIDN'T have oil leaks! Good on you for keeping her on the road though. I've got a soft spot for these things.

Also, I totally just realized you had a lift gate! So neat that these could be had with both a lift gate, and a tail gate. I personally had the tail gate in mine, and used it as a chair all the time.
Thanks! It would be hard to get rid of this truck, it's been great for the last decade. Lots of miles and memories too, took my wife on our first date in it actually.

Yup I have the lift gate. Usually wishing I had the tail gate model, especially because I can't seem to find shocks stiff enough to keep it from bonking me on the head in the winter. And the lift gate is not as rigid which is a slight concern with the spare tire carrier... But it does make it easier to load things in the back.
 

reaver

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Thanks! It would be hard to get rid of this truck, it's been great for the last decade. Lots of miles and memories too, took my wife on our first date in it actually.

Yup I have the lift gate. Usually wishing I had the tail gate model, especially because I can't seem to find shocks stiff enough to keep it from bonking me on the head in the winter. And the lift gate is not as rigid which is a slight concern with the spare tire carrier... But it does make it easier to load things in the back.
I got new lift struts for my X from Amazon. As long as you get the correct length, they're pretty universal.
 
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