Overland Vehicle Outfitters

Project Flatfender: The Frame

Frame
Every project has to start somewhere, and with a vehicle this old it usually begins with some intense cleaning.  The 1970 CJ-5 Renegade platform came as a rolling chassis with engine, axles, suspension, steering, wheels and tires installed.  This greatly simplified inspection and cleaning since I didn't have to work around body parts.  So after plugging all the “holes” in the engine, I fired up the pressure washer to remove as much dirt and grime as possible.  This CJ was a southern vehicle, and it had a peculiar red clay coating much of the frame that defied the pressure washer.  I determined that I would need to sandblast the frame to scour off the dried mud.  For now, I was able to thoroughly inspect the frame and found it to be in very good condition.  The C-channel design of the frame rails contributes to the lack of serious rust issues; water and mud do not get trapped as in the later CJ’s boxed frame rails.  There were several minor cracks in the common locations that would require welding.

Sitting astride the front frame rails and bumper was a homemade winch mounting plate with a fabricated roller fairlead. Constructed of 1/2" steel plate, this ugly beast was securely but crudely welded together.  I used a pneumatic cut-off wheel, a plasma cutter, and die grinder to remove it from the frame. This was a painstaking process because I had to use extra caution to avoid cutting into the frame itself. I removed the stock front bumper knowing I planned to replace it with a heavy-duty integrated winch mount bumper.   

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After removing the homemade winch plate, I immediately removed the engine to give myself more room to work.  The engine was securely mounted to my engine stand to await disassembly.  Removing the Ross steering box from the frame was a simple matter of unbolting it and disconnecting the steering linkage.  The steering bellcrank was another matter, as it was mounted to the bottom of the front frame crossmember with three huge rivets.  This meant using a handheld grinder very delicately to grind through the rivets without gouging the frame.  As it turns out, the grinder and I became lifelong friends during the frame "restification".  At this point only the springs, axles, wheels and tires remained attached to the frame.  This made it easy to flat tow the chassis to the sand-blasting location.  The sandblasting setup is shown in the pictures below.  I rented the sandblaster and industrial Ingersol Rand diesel-powered compressor from our local rental yard, and it was amazingly effective.   

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In addition to the frame, I also brought along the grill, inner windshield frame, and the skidplate, all of which needed to be sandblasted as well.  The grill was very solid, with only minor pitting and surface rust.  The inner windshield frame, however, had several spots where the sandblasting blew through the thin, rusted metal.  It will need to be replaced. 

As you can see from the pictures below, the sandblasting results were fantastic - even better than expected.  Not only did it remove the dirt, clay, and surface rust, but it left a rough surface texture that was just coarse enough to provide the "bite" required for a really durable chassis coating.  In addition, it provided a great welding surface for the several spots that required reinforcement or spot welds.  These included 1) a hairline crack on the front driver side frame horn above the spring mount; 2) a couple of similar cracks near the forward rear spring mounts; 3) a crack on the OEM rear bumper, which will serve as a mounting point for the Smittybilt bumper and tire carrier; and 4) two small cracks on the OEM welds joining the rear v-brace to the frame rails.    

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rear_hanger_crack.JPG
grill2.jpg
Hanger_Removal.jpg
New_Hangers.jpg
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As you can see in the last picture above, in addition to welding on the new spring hangers, it was necessary to cut out a portion of the v-braces on the underside in order to provide clearance for the new MTS fuel tank.  The CJ originally came from the factory with a small underseat tank.  In order to fit the oversized under-body tank high enough within the frame rails, a little over three inches had to be removed from the center section of the braces.  In order to restore some strength and rigidity to the v-brace, I welded in a cross brace.  (As a side note, it's interesting how crude the OEM frame welds appear, reminding me how spoiled we've become with robotic and/or TIG welds.  The upside is that my welds now look right at home and are hard to distinguish from OEM!)  Once all of the frame work was completed, I cleaned the frame surface and then coated it with POR-15, a specialty chassis coat product.  POR-15 must be topcoated if it will be exposed to direct sunlight, but a topcoat is unneccesary otherwise.  It forms a rock hard barrier, completely coating any rust and preventing future corrosion.  I also used it to coat the rear axle housing and tubes, as well as the the main skidplate and drop brackets for the fuel tank skidplate.  The finished product is a nice glossy black; living in the rust belt makes a strong chassis coat a necessity.   

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rear_frame.jpg
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With the frame coated, I turned my attention to installation of the oversize MTS fuel tank.  Included with the MTS tank is a pair of drop brackets and tank straps to secure the tank in place.  This kit is intended to be used with the stock '70-75 15-gallon CJ skidplate, which is readily available and inexpensive.  With the rear v-brace previously modified for additional clearance, I turned the frame upside down on the jack stands and began test fitting the tank, drop brackets and skidplate.  I marked the frame crossmembers for drilling using the drop brackets as a template, and then drilled out the mounting holes in the frame crossmembers.  I then bolted the brackets to the frame, with the tank situated between, and positioned the skidplate on top for fitment.  It took a little pushing and prying to get all of the holes lined up just right, but everything bolted together beautifully.  The height of the tank was perfect for the skidplate/drop bracket combination; in fact, the tank snugged up against the modified v-brace so well that the top strap intended to secure the tank was unnecessary. 

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With the fuel tank situated between the frame rails, it was time to check for clearance of the springs and shackles.  I turned the frame right-side up on the jack stands and bolted on the rear shackles and spring packs.  There was no spring or shackle interference with the tank or the skidplate, even at full compression and droop.  While I was installing the suspension pieces, I bolted on a new set of four Prothane polyurethane bumpstops.  The original rubber stops were nearly worn flat.  The new poly stops bolted into the OEM holes and they are nearly 1.5" taller than the originals, which will help keep the lifted suspension from over-compressing.
 
I'm very satisfied with the way the frame turned out.  I was thorough in my cleaning, sandblasting, and identification of problems such as minor cracks, worn spring hangers, etc.  The POR-15 will provide years of rust and corrosion prevention, and the removal of the old Ross steering pieces made room for a much more modern and effective steering arrangement.  The installation of the 21-gallon polyethylene fuel tank under the Jeep will permit more exploring and the solidly mounted skidplate protects the rust-free tank.  Overall, it's a solid foundation for building my flatfender.  

E-mail us at:  rmiller@ovoonline.com

Overland Vehicle Outfitters
Marysville, OH 43040