1990 GMC crew cab build
 

So I have been the classic forum stalker here for a long time and never had reason to post.

This spring I bought a 1990 GMC R3500 crew cab and an 86 GMC K3500 with the anticipation of combining the two to replace my tired daily driver Cherokee.

Although the project is still a work in progress I wanted to share my work to date since I had done ALOT of reading to see how if and how this was really going to work and read alot of contradicting posts. I wanted a crew cab squarebody 4x4 and to try to buy one that was in reasonable shape was nearly impossible. Everything that I looked at was either roached beyond repair or the owner wanted a literal arm and a leg.

I found this 1990 2x4 350 automatic for $1500. The body was nearly free of rust and interior, the motor had a bad head gasket and the paint was rough at best, but it was my best chance at building what I wanted. Two weeks later I bought a local 86 GMC K3500 dump truck with a 6.2 diesel, sm465 and Dana 60. SOLD.

SO the demo started and I was left with a literal ton of junk or spare parts, sold the dump body and plow setup and made most of my money back, and will scrap the junk when the project is done.

I work a full time job and have two kids so I cannot promise that posts will be regular, but ideally the truck is on the road by the end of December when the Jeep runs out of inspection.

Re: 1990 GMC crew cab build
 

Cool project. Ambitious schedule!

Re: 1990 GMC crew cab build
 

Ambitious for sure, unrealistic perhaps, gonna give it a shot for sure! I do not plan to be able to call it "finished", my goal is to pass inspection.

I have been following along on your build MTCK, very impressive.

Re: 1990 GMC crew cab build
 

Mine was supposed to be functional by June...it still isn't. I am also a dad that works for a living, so finding time to work on my projects is always a challenge. Good luck with yours, I'll be following along.

Re: 1990 GMC crew cab build
 

I do have to clarify that I did not drag the truck in yesterday to start this process. I actually started a few weeks ago, and although I still think January 1 is a lofty goal, I think I still have a shot. Here is some of the work to date:

Pictures in no particular order as I took them this afternoon:

rear of front shackle mount installed

front spring mount attached

view of front 2wd crossmember with control arms mounts cut off

view of clearance between D60 and front 2 wd crossmember ( will have to trim some more as there is only about 3" of travel)

6.2 diesel, sm 465 and np 205 installed

Re: 1990 GMC crew cab build
 

sorry didnt attach pics

Re: 1990 GMC crew cab build
 

Looks good! What are your axle gears? What are you going to use it for when done? I had a 6.2 and it got great fuel mileage.

Re: 1990 GMC crew cab build
 

The front rear is 4.56, not sure on the back. Had to use the 90 srw rear and 85 front so i am sure they are different but havent confirmed yet.

My intentions are to use it for family and toy hauling, camping etc. My 01 Cherokee has been very good to me but it is tight with car seats and the rust is taking over.

Marcus, I read in your build you used bucket seats in the front and saw in a pic that you used a piece of flat stock to make up the difference between the floor and the inner mount. Did you leave it that way or did you come up with another solution?

-Jim

Re: 1990 GMC crew cab build
 

Jim, those front inner seat mounts were actually out of the suburban that I took the seats from. They are spot welded onto the floor from the factory and I just bolted them into my truck. I did the same think on my '77 daily driver truck and there may be some better pics there.

Your truck will be perfect for family and toy hauling. Probably won't set any land speed records with a 6.2, 1:1 trans and 4.56's, but it'll pull great.

Re: 1990 GMC crew cab build
 

Front dually hubs at the machine shop getting turned down

Re: 1990 GMC crew cab build
 

you should just make the dump a 2wd and sell it off.

Re: 1990 GMC crew cab build
 

This looks like fun. I love a good 2wd to 4wd swap! The diesel is a plus as well!

How is you pinion angle up front. I started out like you did just bolting on the front supports and my pinion was pointing down somewhat. I know you can bandaid it with shims but that screws up your caster angle somewhat. Have you looked through my build?

Re: 1990 GMC crew cab build
 

so as predicted and forcasted by others, my timeframe of the end of the year is quickly slipping away. I have had some opportunity to work on the truck, but unfortunately progress is not what it needs to be.

- New fuel tank is mounted
- rear suspension is 1/2 torn apart for the new ORD shackle reversal mounts, bushings, shackles, and 4x4 front mounts

Parts waiting in the wings for tomorrow (hopefully)
-fuel lines
-wheel cylinders and rear brakes
-fuel fill hoses

Re: 1990 GMC crew cab build
 

pinion angle does not appear as though it will cause any problems, but I am still sitting on jackstands. once I get the front hubs back and everything together I will get a better view of it. I will have to look for your build though!

Re: 1990 GMC crew cab build
 

This is a big project. Keep plugging away and you will get there. Funny thing is I am good at estimating how long it takes to do something at work, but terrible at estimating how long it takes me to complete truck projects. I blame all the unknown roadblocks that pop up!

Re: 1990 GMC crew cab build
 

I hear ya! The advantage to estimating jobs at work is that I get to dedicate an almost unlimited amount of resources in an 8 hour day. Home projects? Not so much! Kids and wife are very good at filling the path with seemingly insurmountable constraints. Ah well, c'est la vie.

Re: 1990 GMC crew cab build
 

did you get this done yet? i'd like to see it when you get a chance.
great build BTW!

Re: 1990 GMC crew cab build
 

Not yet. Should be any day though. The attached pic is one a friend sent me of the same job.

Re: 1990 GMC crew cab build
 

i had an 88 dually and would of liked to turn them down.

Re: 1990 GMC crew cab build
 

Haven't got the hubs back yet, but machinist says this week.

The rear suspension is all installed minus the rear. I thought I was going to be slick and reuse the 2wd full floater rear. Since the spring perch mounts are narrower on the 2wd I have found an sf rear local for pretty cheap which I intend to pick up this week sometime the the back end should be a roller again. Although someone could probably clarify this, the rear from a 1990 gmc 2wd spring perches are narrower then a mid 80's 2wd rear. It appears the rear perches need to be in the neighborhood of 43 1/2" on center.

Although I don't have any interior pics to show I have been installing the trim that came with the truck. I will be a few pieces short and will need to source a headliner but I have no problems running without one for now.

So I have clearly missed my end of year deadline to get the truck inspected, but the Cherokee is only 10k miles short of hitting 200k, so my new plan is to continue wrenching on the truck and get 200k miles on the Cherokee.

Re: 1990 GMC crew cab build
 

or cut off the spring perches and weld new ones on in the right location.....

Re: 1990 GMC crew cab build
 

This is what I would do if you have any intention of working or wheeling the truck. Which has the correct gear ratio for what you want?

Re: 1990 GMC crew cab build
 

Got a sneak peak of the shave hubs from the machinist. Have to take the other rotor for him to press the new races in and i can put the front end back together! Turns out one of the hubs was cast with the dually flange and the other was welded which must mean that one was replaced at some point when you could buy a whole assembly.

Re: 1990 GMC crew cab build
 

I will end up welding new plates on the rear. I don't know what rear ratio I want or even what ratio the rear is. I had an 86 Chevy with a small block, sm465 and started with 2.73:1 rear gears and got 20+ mpg on the highway. Ended up blowing the rear diff and put some 8 lug 4.56's. Man she was quick, got to shift pretty fast but top speed was somewhere around 55. I want to be able to cruise on the highway but want to be able to pull pretty good too, so maybe somewhere in the 3.73 range. The plan for now is to figure out the ratio and get a driveshaft made. If it suits then great, if not then start swapping. The front diff is 4.56 so it will probably have to be changed regardless.

Re: 1990 GMC crew cab build
 

that new hub looks great.