04 January 2011

hurtlocker truck - rearend wrap up

I've been really trying to wrap this frame up to get ready for paint,
but first there were a couple hurdles to pass...


I was hoping that the stock torque arm would magically fit,
but of course that wasn't the case.
In addition the stock crossmembers were about an inch too low,
so first they needed to be trimmed.

notching crossmembers

Each crossmember had to be notched on both sides,
so it was a little time consuming.
Gotta love that stool!

notched crossmembers

Remember the rearend doesn't bounce up and down with an independent suspension,
so only an inch or so of room is really needed.

There were a couple options of extending the torque arm,
either just adding a foot and a half with new aluminum,
finding another stock corvette tork arm and grafting the two,
or making a whole new one out of steel or aluminum.

**There are kits and homebuilds that eliminate the torque arm,
replacing it with a crossmember that bolts directly to the 2 holes in the pumpkin.
Fortunately with the internet I've seen enough failures in this design to not want to do this.
Since there is so much torque wanting to flip the pumpkin up or down,
I figured the modified C4 design to be the most bulletproof,
as its really just a simple lever.

With all the choices,
decided to just finish the actual frame first.

rear frame before

First off was boxing the rear,
and make some space for a rear fuel tank.

sectioned rails

After removing that rear crossmember,
I noticed that the bottom of the frame was sectioned a little bit,
so trimmed the top rail to match.
It surprised me how flimsy the frame was without any structure,
so I made sure to take a bunch of diagonal measurements.


Since the frame was kicked up,
I figured it might be better to flip the rear crossmember so it dipped down,
just in case it interfered with the bed floor.
It looked alot cleaner this way too.


A bit later the frame was all boxed up and very solid.
The diagonals of the frame actually were better than when I started,
as it was about an 1/8" inch off and ended up almost perfect.
A huge concern with all the welding those plates needed.

With that all wrapped up, it was time to figure out the tork arm.
I chose to extend the stock one with aluminum plate,
as it seemed the easiest, the fastest, the safest and the cheapest,
hopefully it would look OK too!
If it didn't turn out right than I could go to plan B-D...

the first cuts...

The first cuts are always the most important,
and I figured it best to stagger the weld joints so it wouldn't shear off!


I was surprised how much slop was in the 2 pieces when they weren't joined.
They wanted to twist around, nothing clamps and wire couldn't fix.
After making some plasticboard templates,
this really seemed like the right choice.

mocked up

The driveshaft  had plenty of room...


Aluminum MIG welding is a nasty job.
Lots of smoke and splatter come out of that spool gun,
and lying on your back welding takes the cake.
For some reason I don't mind it, maybe its the end result, I really don't know.

At this point I was satisfied with the strength of the support,
but it looked like 3 plates welded in between the 2 pieces,
which it was.
I could foresee the amount of welding and grinding it needed,
and was really hoping it wouldn't warp.
Unfortunately it had to wait as other obligations came up.

90% done

Finally one evening I made the time to clean the tork arm up a bit.
The holes really helped camouflage the new and old pieces.

whew it fits

So nice when something comes out better than expected!


Fortunately the tranny/engine angle and the pumpkin angles all worked out,
and the alignment looked spot on.

stool time

Did you notice how perfectly the rear sway bar fit? and the shocks?
Really got lucky with the melding of the 1985  C4 corvette and the old 1956 chevy pickup,
so far...

paint prep time

With the tork arm basically finished,
the rearend can be pulled off,
and all the hard to reach welding and grinding can get wrapped up.
Ken already started scouring the frame,
so hopefully we can slap some primer on it soon.

Stay tuned...


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