So....you've decided your truck is a wee bit too long
and you'd like to shed a few inches off the rear? Sounds like you need
to bob your bed. Here I'll explain how to go about shortening your truck
for better clearance and greater departure angle. There have been some
good articles in the past on bobbing. I hope to add just a bit more info
to the tips presented in those to help you on your way. The job is not that
difficult it just takes some patience and careful measuring and cutting.
Like my dad always told me, "Measure twice and cut only once, not the
other way around".
Planning the Surgery
The truck we used for this project is the '88 Xtra
Cab shown here. We started by removing the bumper, license plate,
taillights, tailgate, and inner bed panels. Before we bobbed the bed we wanted
to trim the rear fender skirts for added clearance on the tail end.
We applied some masking tape over the areas we expected to cut. This
was done for two reasons: it provides a good surface for marking your
cuts and it helps protect the paint when you're dragging a saw across
Leaving the plate mount....for now
About to trim the lower skirts to gain clearance
When trimming the rear, I like to be able to mount
the bumper as high as possible. On a truck, the bumper needs to remain
about one inch below the bottom edge of the tailgate to allow for
clearance when the tailgate is opened. As such, we trimmed all the body
panels behind the tires about ½ to ¾ inches below the tailgate. When
you trim under the taillight pockets you will also have to trim the
inside reinforcing panels as well. Remember when doing this you will
have to leave some of the license plate mount unless you intend the
relocate the license plate up higher on the tailgate or bumper.
Measuring forward from tailgate for our first cut
I have tried several methods of cutting sheetmetal
and each has advantages and disadvantages. A metal cutting blade in
the circular saw makes nice straight cuts, but leaves the edge a little
ragged. Saber saws or large reciprocating saws work well and cut
smoothly with fine tooth metal blades. You just have to hold the
saw a little steadier to get a nice, straight line. Die grinders
can also be used in some places. I typically use a combination of
these tools depending on the particular area I'm cutting. In any
case, a little cleanup with a fine metal file will
help smooth the metal edges.
Marking vertical lines for the first cut
So, we sliced off the bottom areas as you can see in
the next photo. Next, we marked our first bed cut. We clamped a scrap
piece of aluminum angle to the top of the bed and used a drafting
t-square to draw our first cut line on some masking tape. This first
cut was made about 7 inches from the inside rear of the bed or tailgate.
This keeps some of the straight bed panels with the tail section and also helps
avoid cutting the tabs that hold the inner bed panels.
Making the first cut
With both sides marked for the first cut, we made
the vertical cuts. To make the horizontal cut across the bottom of the
bed, we used a straight edge. We took a scrap piece of thin steel
flat bar and cut it to length to fit across the inside of the bed. We
tack welded it in place and used it as a guide for our saw. Be sure
to watch for wires and frame rails under the bed while cutting. With
the bottom cut made, the tail section of the bed was removed. No
turning back now....
Second cut complete
This is when we made our second cut lines. Since the
main idea was to get the panels to fit back together as closely as possible,
we used the actual resulting cut line from the first cut to measure for
our second cut line. Simply measure forward from the rear edge of the bed
and mark your second cut line. We decided to remove 14 inches from the bed.
The second cut was made the same way as the first, and the middle section
of bed removed.
Cutting the frame rails
With the bed cut down, you'll want to decide where
you want to cut the frame rails. For our bob, we cut off about 7 inches
of the frame rail. We used a metal blade in a circular saw to make the
cuts. For future reference, we'll need four holes with which to mount
our new bumper. Two will be provided by the existing rectangular holes
just forward of the shackles. The other two will be drilled in the
frame rails. Each bumper mount hole will also be sleeved with a piece
of tubing to prevent crushing the frame rail when the bumper bolts are
Putting it back together
To put the bed back together we aligned the two bed
sections and held them in place using some wood blocks and c-clamps at
the top bed rail. Check for fit and alignment and adjust or grind small
areas as needed. When the mate looks good, you're ready to tack weld the
sections together. However, first we used a grinder to remove the paint
near the edges of the mating sections. Place a tack every inch or so,
making sure the panels mate evenly as you go. Tack both sides and the
bottom of the bed.
Finishing up the welding on the bottom of the bed
You can finish the body welding as you please. I
used a 110V mig welder. I'm no expert welder, so it took me quite a
while. To make welding the sides a little eaiser I added some narrow
sheetmetal strips to the inside of the bed. This helped reinforce the
bed sides and made welding easier due to less burn-through. Go slow
and do not spend too much time in any one area without letting it cool
some. This will help reduce warping of the panels. Luckily, the shape
of the panels causes slight metal pull of the weld joint inward
instead of outward.
When the welding is complete, follow up by grinding
the welds flush or just below the level of the panels. Body filler
can be used to finish the job and provide a smooth finish.
Here are the trimmed inner panels
A quick look at the final bobbed bed profile
Frame rails trimmed, ready for a new bumper
The inner body panels can also be shortened and
reinstalled. Simply mark and cut to length, discarding the tail piece.
If you've cut your bed
similar to the way I described above, you should find the mount
holes will work out fine.
When the bed is bobbed such as this, the rear-most
bed mounts are removed. This reduces the number of bed mounts from
eight to six. However, spacing works out well for the remaining bed.
The taillight wiring will now be longer than necessary. This can
either be spliced and shortened, or simply bundled and tie-wrapped
under the bed.
If you'd like to see my original article when
I bobbed the bed on my truck,
just click here.
Now, with a shorter bed you'll find getting
around obstacles a little easier and the tail won't drag on the
rocks like it used to. Besides....it just looks cool too!
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