1990 K5 blazer/1991 K5 Jimmy


Active member
Feb 8, 2023
Well guess I’ll start this thread! I lost a lot of pics of both of these K5s but I’ll highlight what I can and keep track of them better on here moving forward.

So here’s where it all began for me, just a plain old base model 1990 blazer that I purchased right out of college. Found it outside of Montrose Colorado on Craigslist, 350 with a 4 speed manual. Knowing the manuals weren’t very common in them, I bought it. Got it back to AZ where I slapped a cheap set of steel wheels on it with some BFGs... plus a few maintenance items like a radiator, clutch, and a flowmaster. From there I daily drove and wheeled the shit out of it. It was surprisingly capable in stock form even with open diffs, 3.08 gears, and a 30” tall tire

Then I decided to upgrade the rear end, I had sourced a cheap 9.5” semi float 6 lug 14 bolt for it so I posted the Stock 10 bolt for what seemed at the time a pretty high price. It sold right before my friends from Michigan pulled the trigger on a summer wheeling trip we had been talking about for years. So began the shit show of trying to get this thing “built” in a couple months prior to meeting them in the mountains

(Long boring detail section)
I really had no clue what I was doing. I just wanted it to “look cool” and ride smooth. So I called up Offroad Design and they did a solid job of getting me pointed in a direction with a limited budget and timeline. Ordered up a set of their custom leaf springs, extended brake lines, sway bar disconnects, shackles, and some Ford shock mounts for the front.

They wouldn’t share with me the valving they liked on Bilstein shocks so I ordered a set of 14” 5100s from them. I ended up sending them back after looking up the valving and ordering the remote reservoir equivalent from summit. Working with limited space out back for shock mounting I was looking for every inch I could get while retaining the stock rear shock mounts. The 5165s kind of split the difference between a 12” and 14” 5100 at 13 or so inches but at a compressed length comparable to a 12” 5100.

As far as axles go, I left the stock 10 bolt front paired to the upgraded 14 bolt in the rear. Both got 3.42 gears since the 4spd doesn’t have OD and I like to go 75 on the highway. I wasn’t looking to go taller than a 33” anyway. Rear 14 bolt got a True-Trac, front got a regular clutch style posi (all I could get for that later series 10 bolt)

This ended up being such a time crunch that the springs wouldn’t make it before the trip to Colorado. So I had the springs shipped to Ouray, and everything else shipped to AZ. I busted the stock springs down and cycled everything with the new shackles to get as close as I could for shock mounting and pinion angle before welding shock mounts and spring perched on the housing. Same story up front before mounting the shock brackets. Shock placement ended up working out but pinion angle didn’t... so shims it was.

So at this point... on the trailer it went, and up to Colorado the next day. Springs showed up that afternoon at my parents place in Ouray so me and my buddy proceeded to drink beer and install them. I ground the shit out of the tabs on the front CV and otherwise hoped for the best with the stock drive shafts and hit the trails

Drivelines popping and all it was a successful trip with not one single issue. As soon as I got back I did the fixed yoke mod on the NP241 so I could get measurements for a set of Tom Woods drive shafts. I ordered up a set of pinion shims for the back and got some axle offset plates for the front to help try and mitigate some of the tire rubbing issues (because I HAD to order 10 wides 🤦🏻‍♂️) After that it was once again a daily driver

The scatter brained build actually proved itself to be an awesome all around use vehicle. I could drive it from AZ to wherever, wheel it, then drive it home. Tow the boat to the lake on the weekends and drive it to work during the week. It wouldn’t break the bank in fuel and was fairly comfortable considering. That was until I got caught up in some shit weather in Colorado and a patch of black ice decided to end my fun with this truck.
Fast forward 3 years and a couple other K5s that I had bought and sold, I tracked down this 1991 GMC Jimmy in Farmington NM. 300k miles, torched engine, white, but otherwise identical in build. 350, 4 spd manual. So home it came

Tear down ensued. I still had everything from the old blazer to throw at it besides a tub and a frame. Drivetrain survived the crash with the exception of one rear shock and a rear axle shaft

After some pressure washer love I began to transfer some interior parts from the blazer
Then it was on to transferring axles and suspension... and one new rear shock
New tires and a couple new wheels and we’re off to a good start!
The last push before Easter Jeep Safari that year. As fate would have it I got layed off from my job in Colorado right after KOH so I had some free time to knock this thing out. So more tear down happened

Side note, 28ft deckover trailers make great mobile work benches

Poor steering geometry combined with shitty squarebody frames left a bit of a mess behind the steering box. So with some effort and a welder that was fixed up. Not pictured is I drilled the end of the cracks before welding them all up.

Then on to fixing the seat mounts in the floorboards...

After a final cleanup it was ready for re-assembly with the blue blazer parts.

Slinging parts...

I salvaged the exhaust but had to build a new tail pipe. For the record I’ve already beat it to hell on rocks

I opted for the dual headlight core support and chrome grille. My OCD took over and I made sure everything went back as the factory intended.

And like that it was back together. Only issue after assembly was I bent a tab for the printed circuit board in the gauge cluster causing the gauge lights to not work. Otherwise... No shakedown just drove it straight to moab to go wheeling the following week. Not one single issue on the whole trip 🤙🏼
As time goes I'll keep building on this thread, but at least for those interested thats the back story on this pile. I have a long list of corrections and upgrades planned for it in the coming year. some of those things:
-crossover steering
-shock and shock mount upgrades
-different tires/wheels
-rock sliders
-spare tire carrier
-transmission crossmember/skid plate
-rack or something to secure all my stuff in the back
-bumpers, lights, radio, console, etc

...stay tuned
holy smokeys.

good fucking job!
this thing looks titties!

keep the updates coming. plan for paint? seems like the only main,, big thing left!
then again, i have read none of your posts. just looked at the pics. hahah

i should prolly read everything. prolllllllllllllly
holy smokeys.

good fucking job!
this thing looks titties!

keep the updates coming. plan for paint? seems like the only main,, big thing left!
then again, i have read none of your posts. just looked at the pics. hahah

i should prolly read everything. prolllllllllllllly
Thanks dude 🤙🏼

Paint is super low on the priority list, mainly because I have a habit of driving it between trees, someday though.

I'll probably maintain the jimmy and leave it be after a few upgrades. I Still have the wrecked blue one I want to get started on soon so that one will absorb a lot of time and even more money, but that one will be the “go fast” build. Pretty stoked to get my head into that side of off road
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I’ve had a soft spot for Jimmy’s for a long ass time. Dad had a 1980 Jimmy 4x4 350/350 that was all stock but we’d go out “off roading” every so often, then sold it when I was about 7 or 8.

Always wanted to build a 2wd prerunner version but seems the vehicle never fit my hobby so I’ve not done it.

Love your build and reading along. Keep on keepin on with it!!! Ever thought about doin a nv4500 in it to get OD or do you want to keep it factory 4 speed?
Ever thought about doin a nv4500 in it to get OD or do you want to keep it factory 4 speed?
I have thought about it, when I started on the blue one I had a 2wd NV4500 sitting on the shelf. At the time the cost and effort didn't outweigh the benefit for me, mostly because I didn't want to mess with altering the floor and shifters. Converting the transmission and rebuilding it would've been an extra 2-2500 if memory serves me. After having no OD for this long I'll probably consider it one day if a deal comes along on an early GM 4wd NV4500, because then I can go to a 4:10 gear ratio... But until then I'll just back out of the throttle a little on the highway.

SM465 4spd
6.55:1 first, 2.72:1 low range, 3.42 gear ratio.... 60.93:1 final in first, 72 mph at 2500 RPM

Early GM NV4500
6.34:1 first, 2.72:1 low range, 4.10 gear ratio.... 70.7:1 final in first, 72 mph at 2250 RPM

(Edit: I think I calculated that right this time)
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Well I was hoping to do some steering upgrades at least before going up to Colorado this summer but the throw out bearing said otherwise. Naturally I didn’t order enough parts so now I wait... 6B5FF49F-1813-4601-A1E0-5883611AD0A1.jpeg
Finally found some time to get a console put in last week. Decided to go with a Tuffy 12.5” wide console with the single din radio compartment. At some point I’ll use the radio compartment for a switch panel when I get around to adding lights and other stuff to it, but for now I’ve at least got way more storage and a place to mount my radio and fire extinguisher 😂

The bracket was the most involved part of the install, all I had was some scrap 1/8” plate laying around and nothing but an angle grinder with a cutoff wheel. Kept the mount simple to use the original holes in the floor (drilled larger of course). Back then GM had a habit of not centering seats in the cab and that really screwed with my head getting the console centered up.


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