How To convert LWB into SWB (pics)

[gflo383]

I just completed the conversion and have taken several pictures, and this is my attempt to try and explain how to do the conversion.

my truck is an 86 2wd long box silverado. it was from out of state and luckily has no rust, this made welding very simple.

First Place your truck on a flat hard surface like concrete, somewhere it can be lifted by a roller jack and placed on stands.

Remove the box by removeing the 8 3/4headed nuts underneath the bed. remove the two ground wires near the filler necks (one if you have single tank) there is a wire harness at the rear of the box, unlplug it and the tail lights and box harness stay with the box. also, remove the hose for the rear diff, it is fastened directly above the diff. once the box is removed do not set it down on the bottom, it will crush. stand it up on end.

Jack up the cab just enough to load the jack. using a long 4x4 or or something strong that will span the width of the frame. after it is loaded i used two jackstands and slid them under the frame near the rear of the cab.

this picture is after i cut and welded but this shows you how to measeure back from the rear of the cab. i measured back 9.25" and scribed a line all the way around the outside of the frame. from this scribe line measure 14" back and scribe again. this section is going to be cut. make sure you cut very square as these to cuts will be butt up and weled together. before cutting anything though, the gas tank(s) drive shaft, wire harness and brake line must be removed. To remove the gas tanks i removed them still fastend to the brackets. there are 8 14mm headed bolts holding the brackets and 1 13mm bolt near the front on the bottom holding the plastic cover. the ground wire(s) are held in place with a 13mm bolt as well. remove the driveshaft with 11mm socket at rear diff. for the brake line i just removed the 13mm hold downs and pulled the line away.

ok, now that the tank(s) have been removed, all lines and wires are out of the way and the driveshaft is disconnected, you can cut. I cut the scribed line closer to the rear first. this way when you cut the second scribed line, it is solid due to the jack stands and jack. after cutting out the 14" section, roll the rear end forward and but it up to the cab frame. useing a few pair of vise grips, hold it in place and tripple check everything is square in all directions. if it isnt, then make it! tack weld it on top of both sides and check for square agian. once it is 100% square in all directions weld in about 2" incrimnets on both sides to help prevent it from warping and or pulling one way or the other.

once it is completely welded, cut a piece from the 14" section and weld in a "fish plate" the goes over you weld. be carefull not to cover the holes for the gas tank bracket.

now go to the rear of the frame. measure 6" and scribe a line all the way around. remove rear cross brace and relocate about 4" forward, the holes are all ready there, just bolt it in. cut the scribed lines, and paint them to prevent corrosion.
this is a pic after it was cut



once everything is cut, welded, bolt and finshed on the frame, install 16 gal shortbed tank(s) in the same location they were removed from. my truck already had 16 gal tanks, so this may be different for someone whom had the larger tanks. 4 holes may need to be drilled for the rear bracket.

after everything under the truck is comletley back together, you can install the box, plug in the harness and go cruzzz.

i have a 2 piece drive shaft and i am getting the rear section shortened 14".

if there are any questions please ask. hopefully this was a little help!

here are a few more pics.



this shows how i didnt need to drill for the rear gas tank bracket




thanks for looking,

Joe (gflo383)

[68GMC454]

i recomend that you box the frame,,or at least grind donw the welds,,and run a piece of plate over the inside of the frame and weld the heck out of it...most guys who cut there frames cut them different for better support when finished...but i would definatly weld a plate over the finished area..but its your life in your hands...

[hiway]

Nothing against your welding skills but I agree that you need to plate it. The heat weakens that area and it needs a little extra plate or boxing to put the flexability back in it. Just my .02

[KMK454]

Very cool conversion, good work!

Any more info on that all stock 88 Iroc? I see it in the background of one picture! Third gen camaros are my absolute favorite. My dad had a 91 with 22000 miles that he sold last May

I want a low mileage, all original 5 speed V8 really bad, but they're hard to find.

[87 STEPPER]

Yeah like the others have said you really need to gusset that area or box that section of the frame otherwise you may have a failure there.

But it looks like a nice conversion.

Maybe in the furture you can find a short bed frame in good condition in the junkyard and then swap everything over to it.

[gflo383]

i explain in there somewhere to add a fish plate. its a piece of steal from the area i cut out. i cut it to the correct size and weld it in on the inside of the frame.


the 88 iroc.... its white, the one in the backround is my red one. the 88 is a hardtop, with black interior, 88,000 miles. 350TPI with 3.08 rear gears, and sadly no rear disc brakes on the 88.

ill post some pics in anouther post if your interested in seeing the camaro's.

[ghetto_superman]

um.. that looks pretty good, but hopefully you dont regret not making a 'z-cut', which more evenly distributes the heat and stress of the cut, and also allows you to weld a larger area of the frame which= more strength.. but youre on the right track with the fish plate anyway. nice work!

[Dr. Drop]

I really admire your drive to take that step to shorten your frame. However, I do have a question. Unless "your" truck has a different wheelbase than the 60 to 72 models, (that is 127 inch wheelbase for the longbeds and 115 inch for the shortbeds), how did you come up with 14 inches as the amount of frame to remove? I've done alot of the early ones and I only take out 12 inches under the cab, and 8 inches off the rear. I could be wrong as I have never done a 73 and up truck yet.

[Ironclad454]

DR.Drop - 73-87 trucks are longer than the earlier models. In 1973 they went to a wheel base of 131.5 for the longbeds and 117.5 for the shortbeds.

Looks like a nice start gflo.