Custom 1987 GMC Crew Cab Short Bed

[OYMC]

What is stronger when sectioning a chassis, a straight cut or a "Z" cut?

Answer: "Z" cut.

The edge where the two points of the chassis will be joined together is about 5 3/4" trailing where the chassis begins to taper (Height of chassis decreases in measure). By measuring down 3 1/2" at both ends of cut marks the height of the chassis is nearly split in half. I measured down 3 1/2" from the top edge of the chassis, and placed marks in multiple locations. I then aligned a straight edge to these marks and scribed a line down the length of the chassis being sectioned. *Run the line about 5" past the vertical cut lines. This will help with realignment of chassis prior to welding.

From the mark placed 1 1/2" behind front bed mount hole I measured 5 3/4" forward along the 3 1/2" middle line. I then scribed a "Square" vertical line at this point.

From the trailing mark I repeated this process...

[OYMC]

After placing my marks I double checked my measurements, and measured for square or "Diamond".

Find a reference point on the chassis that is relative in location on both frame rails. For example: a rivet head, factory bolt hole, etc. Now measure from that point to the opposite frame rail where you place your marks. Repeat this process for both sides at least (3) times. If you have two different marks, you have not measured correctly. Recheck both sides, and you will probably find where you made your mistake. Erase your mistake, and remark the chassis. After remarking the chassis be sure to check for square again. If you continue to get bad measurements, there is a chance your chassis is out of alignment.

Now its time to start cutting. I have a bad A$# plasma cutter for these jobs, and it makes the process amazingly easy. Make sure that you mark the section that you are cutting out. This helps to avoid cutting any part that should not be cut... Trust me, mark the chassis!

When making your cut, cut 1/16" to the outside of mark. It's always better to go back and grind a little then it is to cut to much, and have a poor welding gap.

[OYMC]

And the rain comes fallin'

Just as I had test fit the sections together, the rain came falling!

Needless to say, I'm very happy with the results so far.

*Note: Typically you would want to weld temporary braces on the chassis prior to cutting to keep chassis square. On this chassis there are factory cross-members right next to the two cut lines, so none were needed.

Stay Tuned, and thank you guys for the support and interest!

[joe231]

Nice work and nice write up!

[tswore]

looks great! that is exactly where i was a few weeks ago.

[OYMC]

In response to "Tswore"...

After reviewing his build, I realized a few differences in our layout and parts being used.

With this truck I am using 56" long leaf springs. These are the stock 1 ton length springs. *Note a 56" spring is not a 52" spring under load.
In "Tswore's" build he had relocated his leaf spring hangers altogether, and is also using a shorter length leaf spring than what was original (Nothing wrong with that by the way).

I also noticed that the back portion of the chassis had been cut to make up the difference in extra length that was left in the portion of chassis that was sectioned (Nothing wrong, just different layout).

In order to section the chassis like I did the front leaf spring hangers had to be temporarily removed. When the chassis is welded back together, the hanger will be bolted back on to its original location with the exception of one hole that will have to be drilled out.

Great work "Tswore"....

Its always a good idea to review other peoples ideas prior to building a project. In many ways it can save you a lot of time and frustration!

[OYMC]

Time to start welding!

Prior to welding the two sections of frame back together I tack welded a 18" long 2"X2" box tubing along the horizontal line that was scribed 3 1/2" down from the top edge of the frame.

This is helpful for two reasons:
1. It keeps the frame on the same horizontal plan
2. It holds the chassis from shifting left to right (Jack knife affect)

[OYMC]

After checking for diamond, and linear equality of both frame rail, I butt welded the two halves together.

[OYMC]

"Fish" plate time:
Drill out two 3/4" or bigger holes (One on either side of the "Z" weld seem of chassis). Place a 1/4" thick or thicker "diamond shaped" plate on the inside of the chassis, and plug weld to chassis.

Now finish by welding the perimeter of Fish plate to chassis.

[OYMC]

I finished cleaning up the frame rails, and sprayed them with an undercoating to prevent rust.

* Make sure you spray a lot of sealer over your weld work. Water can get in behind the weld job, and over time cause the section to become weak.

[54Caddy]

good old wyotech shop jacket ahahah. you going there or what man?? im almost done just one more class and im done

[OYMC]

Guilty as charged...

I graduated from Wyo-Tech in May of 2009. I took Chassis Fabrication / High Performance Engine Building, Street Rod (Sheet metal fab, and custom paint), and Trim and Upholstery. I left there with a minimum of an "Honors" award in everything I took, and earned an "Outstanding Student" award in Street Rod.

My suggestion to anyone trying to earn a degree in any field of study is to go to school "Stupid".

Its the students who go to school that think they know everything that tend to fail, and typically never fully achieve their goals (Dreams). * There are a lot of those at Wyo-Tech.

I am still furthering my education at a local Junior College, and plan to transfer to a local University when I complete my prerequisites.

I'm not saying I'm the smartest guy in class, but I am the most interested in learning something new, and keeping an open mind to new ideas.

[54Caddy]

yea im in street rod rite now. yea there is a lot of big headed people there that think theyll know it all in 9 months not true. damn you did damn near all the classes except smog and asm. good job man.

[OYMC]

Your right 54Caddy... Wyo-tech is a great source for introducing basic fundamentals of automotive fabrication skills, but its just that, an "Introduction"...

[JohnC]

Frame looks awesome man.

[1Ton]

Looks good.

I'm a Wyo Tech grad from 96! Always wish I would of taken streetrod and chassis fab too.

[ghettoluxury]

keep up the awsome work

[OYMC]

Axle spring perch time!

The rear springs I am using are 56" long, 6" lift skyjacker soft ride leaf springs. Because the front springs are 8" lift springs, I will be adding 2 1/2" to my new rear spring perches to level the truck out.

To do this you should first measure the distance between the top of the original spring perch to the top of the axle housing. Most of your stock perches should be around a 1/2" for this measurement.

Next you want to make a decision as to how deep the perch will set over the axle housing. I decided to drop mine 2" over the top of my axle housing.

Now, you have 1/2" of original spring perch height + 2" of mounting depth + 2 1/2" of additional lift = 5" of overall Material height.

Most Chevy leaf springs are 2 1/2" wide, so the optimal spring perch material for this perch would be 2 1/2" (Wide) X 5" (Height) X 8" (Long) X 1/4 (Thick) mild steel Box tubing.

The length of you spring perch should be around 8". The extra length helps to prevent axle wrap.

My perches are made from 2" X 5" X 8" X 5/16" Box tubing material with 1/4" end caps. I spread the base of the perch to 2 1/2" to give it a more custom look.

If you weld end caps to your perches make sure you leave an opening for ventilation. Moisture can get into the spring perch leaf spring guide pin hole, and over time weaken your welds from oxidation. I always spray the inside of anything that has been boxed with galvanized spray. This will help prevent oxidation and galvanized spray won't melt or catch on fire from the excessive heat while welding.

[OYMC]

The leaf springs are mounted!

Make sure you always use grade 8 fasteners when working with Suspension parts...

*Note: the front leaf spring hanger uses all the original mounting holes except for the front top hole. This hole has to be drilled out into the front section of the chassis. Just one more aid in tying the two parts of the chassis together.

[OYMC]

The Rear axle is under the truck!

Last night my neighbor and I slid the axle under the rear leaf springs in preparation for pinion angle alignment, spring perch mounting, and shock mount alignment and install.

Needless to say I am getting very excited to finish this truck, or at least have it ready for a test drive!

I took a few photos of my wife and son. For some reason they support my sick habits... (Could be worse)

To set your rear axle you should set the leaf springs on top of the spring perches (Perches should not be welded to the axle yet). The full weight of the truck should be on the axle at this point. Slide the frame rails with a high-lift jack until an equal measurement can be achieved from the back of the brake mounting flange (On axle) to the outer edge of the spring perch. Make sure you take relative measurements on either side.

In this application I have 5 3/4" front the back of the brake mounting flange to the outer edge of the spring perch.

Now that your axle is centered between the frame rails, lift the pinion until it looks to be inline with the back of the transmission. Find a nice heavy duty nylon string and tie it to the back of the transfer case, where your drive line will be mounted to the pinion of your axle. Adjust the height of your pinion until it looks as close to direct alignment as visually possible.

Tool time. Attach an angle finder to the end of your pinion and write down this angle. Lift the front of your pinion until it is approximately 4 degrees higher than your original measurement. Once you are certain you have everything in place by re-checking all of your measurements (Including the measurements taken to center the axle) tack weld your spring perches.

*Note: it is important that your drive line is not in perfect alignment with your transfer-case. The universal joints require a slight amount of offset in order for constant universal joint rotation and equal bearing lubrication. If you obtain perfect alignment you will experience premature universal joint failure. As your tires push forward in a normal exceleration situation, the axle will torque the pinion down towards the ground. By setting the pinion angle slightly higher it will achieve perfect alignment only while under exceleration.

Shock mounts:
Now that everything is in place, you can set up your shock mounts. It is important that your shock stays in alignment at both mounting ends. What I mean by that is if you have a top mounting bolt perpendicular to the frame, the axle shock mount bolt should also be perpendicular to the frame. If you mount your shocks otherwise, you could experience binding, and ultimately shock failure.

I'm heading out to setup my axle, and will post pictures later.

[BIG10]

You have a great attitude and it shows in your work. Keep it up. You're doing great things.

[thirdstreettito]

I cant believe I never saw this build! Right on man! I love CC's and 6.2's(im a rare breed)! Subscribed.

[OYMC]

Hold the phone!

Okay, you know that saying, "Never assume because if you do it makes an "As* out of "U" and "ME" ?"

I'll always admit when I'm wrong, and I am way wrong on this one!

I test fit the bed yesterday, and found out the my axle Center line is off by 6"!

After looking at a bunch of pictures of short beds and long beds, I assumed that the difference in length between the two was in the section between the cab and the leading edge of the rear fender. I "Assumed" that the back section (Trailing edge of the rear fender to the trailing edge of bed) were all the same in distance. (Look at the two pictures below and you'll see what I mean...)

NOOOO!..........THEY ARE DIFFERENT!

Just measure...It will save you time and grief.

So, the chassis is perfect. The front bed mount chassis hole lines up perfectly with the front bed mount, and the rear chassis bed mount hole lines up with the rear bed mount.

I have already fixed the axle alignment issue, and I will show you what I did (Very Easy Fix) tomorrow...

In the mean time, enjoy this horrific photo... I will redeem myself tomorrow...Trust me!

The Short bed I have is kind of a piece of junk... I don't know if it's against the rules to inquire for a short bed, but if anyone has a lead on a good short bed drop me a line... Thank you.

[joe231]

So did you take out the full 20" behind the cab?
I'm sure you know now....but you need to remove 14" behind the cab and 6" off of the rear of the frame behind the rear hangers.
Are you just going to move all your hangers towards the rear 6"?

[OYMC]

Alright... I goter' licked!

Check out the photos, and then I'll explain what I did to fix my dilemma...