Making a LWB into a SWB - shortening a '55-'59 Chevy Truck Frame & Bed

[53choptop]

Its been a while since I posted, I have mostly lurked and learned. So thought my next post would be a good one. BTW I used glock35ipsc tech post on shortening a '68 LWB as a reference, measurements are different, but his great pics and description helped out alot to get the jist of the task. Thanks glock35ipsc.

This tech shows how to shorten a long wheel base (LWB) frame to a short wheel base (SWB), in this case my 1957 Chevy. This is a 3600 model with a wheelbase of 123.25 inches the SWB 55-59 Chevy have a 114 inch wheelbase.

All the measurements I got off frame dimension manuals online:

http://chevy.oldcarmanualproject.com...esto/56071.htm

for confirmation, I have my friend-Ruben with a 1956 Chevy SWB that measured his truck frame for me at specific rivet points, cab mounts, rear axle centerline etc.

To make a LWB to a SWB, 9.25 inches needs to be removed from the center of the frame and 5 (I need to look at my notes again but I think its 5) inches from the rear frame horns.

This is the patient going under the knife.

[53choptop]

There were several measurement points on the frame and bed I needed, plus wheel base numbers, mostly all other measurements were taken off the manuals and Ruben's 56. I will use these to "cut and paste"

[53choptop]

I removed the bed, rear axle, leveled out the frame with jackstands and a jack. I tried to keep everything level, you dont really have to becasue your cuts will be made using measurements and not levels.

After researching this site and other sites on the web, this is the best way to cut the frame. It distributed the stress and makes the welds stronger. The total measurement is are 18.5 inches from the rear cab mount, this goes all the way to the first rivet on the center crossmember, which needed to be removed.

The shaded portions are what will be removed, I cut 9.25 inches from the bottom 3 inches of the frame and another 9.25 inches from the top 3 inches of the frame on both sides.

[53choptop]

After the cuts were made on both sides, I joined the frame together, re-measured the wheelbase, reference points from the SWB measurements I got from the manuals and my friends truck, re-measured and re-re-measured just to make sure.

Since I removed a rivet from the front of the center crossmember, the crossmember helped in aligning the 2 pieces together; the rear portion of the frame slid into the front portion.

I used a ratcheting tow strap to tighten the frame together, I clamped the frame at critical point on the cuts, top to bottom, inside frame and clamped it all down.

Measured again....everything good.

[53choptop]

An important part of the whole process is making sure your wheel base is right on. I made a mistake of not taking into account the rear end centerline. It was a faded soapstone line, it took me a while to confirm and get the rear end center line again. Make sure you mark everything down. In this picture, you can barely see it, but that black line on the frame right above the rear end center line saved my butt. After I tightened everything down with the strap the wheelbase was right on e .... 114 inches.

[53choptop]

Separated everything apart again, I cleaned up the cuts, beveled the edges for welding, made plates out of 1/4 inch steel (its a 12x6 "diamond" shape) to weld inside of the frame for strength, put everything back together, clamped, tightened and re-measured one last time.

I installed the rear axle, wheels and re-measured the wheelbase now at 114 inches. I don't have pics of the rear frame cut, but all I will do is just measure from the back of the spring mount to the end of the frame and cut the end off that extends beyond the SWB frame measurements.

[53choptop]

Christmas eve interrupted the build, but I was able to finish up the frame, before we left to visit family (took 4 days off). Here she is sitting in the corner waiting for me to come back from our trip.

[53choptop]

After the break, I came back ready to work. Next comes shortening the bed.

I made sure the bed was square on the jack stands, because the bed frame rails were not too helpful because the bolts had rotted off.

Once it was square, I reinforced the bed with scrap angle iron and rectangular tubing, this is very important to make sure the bed stays square and does not flop on you when you cut it.

Removed the bed steps.

[53choptop]

Once square, I started the measurements, I used the measurements from my buddy’s truck to cut the bed. I took measurements from his bottom front stake pocket to the fender and used that as a guide to measure upwards on mine, remember the fender is not straight at the bed side, it bulges forward, so you need to take the measurement of the bottom fender to stake pocket of the SWB, THEN take that and subtract it from the LWB front of the stake pocket to the back. I know it does not make sense, hopefully the pics help.

Once measurements are made, the front bed panel is bolted off

The bed stake pockets spot welds are drilled out, with a little persuasion, chiseled apart

Now you have a bed without the front panel and bed stake pockets.

[53choptop]

I measured and used tape to mark where I need to cut. Writing what needs to be cut and where really helps because if you cut on the wrong side of the tape you will be off by 2 inches (I'll show you why in another post).

[53choptop]

The cutting begins.

I measured and cut did both sides. The drivers side had a spare tire mount, I just removed that.

I cheated a bit, I did not fold the edge in when the panel bolts onto the pockets, banging on the bed side to make that L shaped edge was going to be problematic, so I cut the edge and ended up welding it to the bed pocket.

I welded in the drilled out spot welds to the bed side

I bolted everything back together.

[53choptop]

The rear portion of the bed was a doozy.

I reinforced the bed right behind the tailgate, removed the tailgate and started measuring. On the rear, cut the entire rear section of the bed right where the spot weld lip is at and just slid it forward.

Separating the sections separately was going to take too much time and probably going to cause more damage than good.

I didn’t take as many pics as I should have but you can see where I cut, slid forward, clamped and welded. I left a 2 inch lip inside the bed that slid over the stake pocket and welded that in.

Now remember when I mentioned cutting the wrong side of the tape, the last picture is exactly that. I miscalculated and didn't mark the tape as I should have and cut the wrong side leaving me with a side top that is 2 inches shorter.

[53choptop]

This is the end result, a SWB bed.

[53choptop]

Installation of the bed.

[53choptop]

There you have it a LWB to a SWB conversion - before and after.

[nuke1]

very nicely done, i also did a shortened frame on a 58

[53choptop]

Thanks nuke1, I was checking your build threads...really cool too. I see you've done a few lwb shortenings. I also see I am not the only one working in a limited space garage, I like how you arranged the 68 to fit in one end of the garage while you work on it and other things

[entourageguy]

Nice info on an often asked question.
I think the mods should make this a sticky on this forum.

[JML55]

Nice work man, i like the mods. I didn't shorten my frame its already swb but i made short box side from a 7 foot box too.

[nuke1]

Originally Posted by 53choptop

Thanks nuke1, I was checking your build threads...really cool too. I see you've done a few lwb shortenings. I also see I am not the only one working in a limited space garage, I like how you arranged the 68 to fit in one end of the garage while you work on it and other things

thanks for the praise, i do what i can in the amount of space i have, you know what i meen. As for the arranging of the truck, i had to find more room, if only i had and extra.........

James

[DennyB]

Great post James!

[53choptop]

Thanks guys, I am attaching a few more pics of the measurements I used from my buddy Rubens truck for reference. This is probably the most important part of the project.

[53choptop]

Last 2

[kttrucks]

Very nice! Looks like you've got a very solid truck to work on.

Good Job.

KT.

[53choptop]

Thanks,

BTW anybody have one of those No Limit Engineering tech videos "Camaro clip in a 55-59 Chevy" they no longer need? Looking to buy one on the cheap.