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Offroad '89 R3500 Crew Cab 2wd to 4wd conversion & beyond

Started out with 2wd TBI350 with SM465 to current 4wd with 454, 700r4, NP241

Overview

before & after of sorts.jpg

Some of you may be familiar with my yellow K5, the General. It's been several years since I posted anything about it. Just been running trails and not doing much work on it. After owning the former military K5 for 12 years, we've reached the point where any new mods are out of my budget and we need a truck that is more family orientated. Plus the truck is just plain wore out.

We found a good deal on a local '89 crew cab Chevy. The only catch is that it's a 2wd. Here it is on the day we bought it.

just purchased (3).jpg


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I think this would be the Scottsdale package. Basic TBI350, SM465, and not much else. It was apparently some sort of public service vehicle in the past. The base color is school bus yellow. Some previous owner rattle-canned it white. They painted the interior black, including the dash and door panels. The paint is peeling off the door panels; and every time I close the doors, flakes of paint float off.

The plan is to swap over the 60/14 and 700/241 from the General. The suspension will be ORD 48.5" leaf springs up front and 64" springs in the rear. The rear sprints will be hung with the 2.5" ORD flip and 6" DIY4x shackles on the General now.

I'm also planning to shorten the wheelbase down to a short bed. We really want to have the full pickup functionality because I'm not only replacing the wheelin' rig but also the Super Duty we had. I'm hoping the for level of trail running we'll be doing, a full bed can survive. If nothing else we'll try it out for a while and see what happens. Worse case, I pull off a severely beat up bed and fab up a flat bed. Heck I've never wheeled a truck this long so who knows how it'll go.

The end goal is a decent looking pickup that I can do some moderate wheeling with and pull a lightweight camping trailer. Something that will get the family out in the back woods having fun. Just a truck. :laugh:

A little summary on the conversion:
I wanted to compile this while it's relatively fresh in my mind.

Things I learned about 2wd to 4wd conversion:

  • The holes for the 4wd components are NOT on the 2wd frame. I mistakenly thought the frames would all be the same and I could just basically bolt in the components I needed. However nothing was there.
  • The engine crossmember is removed with the IFS components and the engine mount brackets for the 2wd are a completely different configuration from 4wd trucks. This was something I didn’t even consider before starting the project. I modified an Offroad Design engine crossmember and the 2wd engine mount brackets to work together. And of course you will need to drill holes in the frame to mount the Offroad design crossmsmber since it was made for a 4wd. Or you can do like I did and drill the new holes in the ORD crossmember and weld up the old holes. I like that idea better than putting a bunch of holes in the frame. http://ck5.com/forums/showpost.php?p=3250904&postcount=166
  • I thought I could use DIY4x.com B-52 brackets to hang the front of the front springs by simply removing the core support body mount brackets and bolting the B52 brackets on. I had assumed the body mount brackets would be the same between 2wd and 4wd. This is not true. A couple holes are close, but not quite there. DIY4x makes no claims about the B52 brackets being used for 2wd to 4wd conversions, I just made a false assumption. There is another reason they are not the “easy” answer I’ll get to next. https://ck5.com/forums/threads/89-r...-conversion-beyond.303347/page-6#post-3234751
  • It seems like the rear hanger for the front springs should be a simple matter of drilling holes for the through-the-frame hanger, and it is. However where this bracket is located the frame is completely different between 2wd and 4wd. What it boils down to is the 4wd frame has a shorter profile to allow room for the rear spring eye of the front spring to swing back and forth on the shackles. This means in order to keep the Springs from hitting the frame you will end up with the rear of the front springs hanging lower on the 2wd frame than they would be on a 4wd. If you leave the springs like this it can affect ride quality and it will make the caster angle extremely positive. In order to fix the caster angle I had to modify the B52 brackets mentioned earlier and drop the front of the springs 3”. The net result was that with 4” lift springs I have 6” of lift. More lift than I planned, but it seems to be about perfect for this wheelbase. http://ck5.com/forums/showpost.php?p=3271264&postcount=265 & http://ck5.com/forums/showpost.php?p=3273274&postcount=266
  • The 2wd transmission tunnel on automatic transmission equipped trucks is too short for the 4wd drivetrain. If you get lucky like me and have a manual transmission in your 2wd, this isn’t an issue. I didn’t even realize this could be a problem, good thing I had a manual trans.
  • If you plan to use the factory 4wd transmission crossmember, you will need to drill new holes in the frame. Or you can do like I did and fabricate a crossmember that you can design to use existing holes. http://ck5.com/forums/showpost.php?p=3309029&postcount=356
  • Probably obvious, but you will need to make a hole in the trans tunnel for the factory transfercase shifter. Another option I took was to use a cable shifter from JB Custom Fabrication. http://ck5.com/forums/showpost.php?p=3330138&postcount=480
  • Another issued I didn’t see coming, the rear spring hangers are 3” shorter on a 2wd truck. This means you need to remove the 2wd hangers and source new brackets at the correct height. If you don't replace the hangers your rear suspension will need to be 3"taller than the front. The good news was the rear driveshaft had enough slip to accommodate the lift. http://ck5.com/forums/showpost.php?p=3265124&postcount=208
  • Update on rear suspension. Installed new hanger brackets for the front of the rear springs. Worked really well, but really tight to the gas tank. Used a shackle flip for the rear of the springs. Only the front 2 holes line up between flip brackets and the frame holes. Had to drill (4) new holes on each side. http://ck5.com/forums/showpost.php?p=3525424&postcount=873 & http://ck5.com/forums/showpost.php?p=3526187&postcount=877
  • Installed 4l80e from 95 K3500 with US Shift Quick 4 controller along with Offroad Design Magnum 4 speed NP205. The Magnum was a thank you from the Blazer Bash crew for 10 years of organizing the event. https://ck5.com/forums/threads/89-r...onversion-beyond.303347/page-172#post-3865173 https://ck5.com/forums/threads/89-r...onversion-beyond.303347/page-172#post-3866868 https://ck5.com/forums/threads/89-r...onversion-beyond.303347/page-157#post-3839324 https://ck5.com/forums/threads/89-r...onversion-beyond.303347/page-157#post-3839369

Specs

Year
1989
Make
Chevy
Model
R3500
Trim Level
Base
Interior
PRP seats, DIY4x aluminum dash
Factory Options
None
Engine
454 with Holley Sniper EFI
Transmission
4l80e from 95 K3500, US Shift Quick 4 standalone controller
Transfer Case
Offroad Design Magnum 4 speed NP205
Steering
Offroad Design crossover high steer and PSC ram assist
Suspension
FRONT: Offroad Design leaf springs & Bilstein 7100 shocks
REAR: ProComp 4" leaf springs with 2.5" shackle flip
Axles
Dana 60 & 14 bolt FF. ARB locker & 5.13 gears in both
Wheels
Robby Gordon type 184
Tires
37" Nitto Terra Grapplers
Paint
White

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