Well, I have decided to follow in the footsteps of a few talented individuals before me and stretch my TJ tub and frame by 15”. A couple examples of my inspiration can be found on the following links (Thank you, Jason and ‘Kelowna’ Mike).
I don’t know who coined the “TJ-6” moniker first, but I like the whole CJ-6 theme… and with their permission, I am going to run with it.
Here are a couple of other 15” stretches I came across in my research.
Truth is, I always wanted an LJ. The advantages of the larger wheelbase and extra interior room can’t be denied. At one point, I was seriously considering trading my TJ for an LJ but the cost of this trade up always got in the way of this plan. It seems like LJ’s are hard to come by in general (I can’t say I blame people for wanting to keep them). Whenever one popped up, they were either high mileage Jeeps with a minimum $12K price tag or just too close to $20K. Considering that at best I can only get 6K for my 99 Sahara with almost 200K miles in the odometer, I knew I was going to pay dearly for it. Then there is the issue of the $6K I had already spent on mods over the years. I was going to have to start all over again (I just put on an AEV highline, I was not about to just give that away!!)
I then came across Mike and Jason’s impressive TJ-6 builds and others like them. As I looked into to it further, it dawned on me that this was something that was definitely within my fabrication abilities and budget.
I am licensed structural engineer by trade but do have some basic know how on metalworking and welding. Plus, I have recently dabbled in bodywork and automotive painting when I did my highline install.
Like Mike, I will use frame sections from a wrecked TJ for the frame extensions and will borrow ideas from the AEV Brute frame extension conversion. I will attempt to repair the 15” tub gaps with 18 gauge sheet metal and body filler (Some creativity will be required to effectively hide the splice seams). I will remove the soft top belt rail on the driver’s side and transplant the excess material to belt rail gap in the passenger side. I will then use a new LJ belt rail for the driver’s side.
Here is a digital previsualization of the finished product:
I will tally up all the material costs at the end along with any money I gained from selling my current soft top and frame from my TJ. So far, the biggest expense has been a new Bestop LJ top and soft top frame ($1000).
Along the way, I will incorporate upgrades to the roll cage, skid plate, suspension, and drivetrain that I would have already done on my SWB TJ anyway.
Well, without any further delay... Here is my TJ-6 build:
After securing all the required steel, I proceeded to measure and cut the 15” frame extension sections along with drilling the ½” plug weld holes. As previously mentioned, these came from a junked TJ.
I then cut ¼” thick wall, rectangular 3” x 4” tube steel into sections for the smaller frame inserts. Using the frame extensions as templates, I sized the ¼” thick inserts to fit inside the frame sections in 8” lengths. I then welded the two halves together into a completed insert as shown on the right side of my welding table. The fitting for this took up the better part of a weekend. Details, details…
On the following image, I have the fabricated 3/16” fish plates that I will place on the interior faces of the extended frame sections; just like AEV does it with the Brute conversion.
I then removed 26” of the passenger retainer belt rail as shown. This was accomplished by drilling out the spot welds with a spot weld remover bit and then carefully prying off the rail one section at a time:
I also removed the entire retainer belt rail on the driver’s side:
As previously mentioned, I will use sections from the removed driver’s side retainer rail to complete passenger side retainer rail gap. I bought a new LJ rail (black) for the driver’s side.
Let the hacking of the tub continue! I drilled out all the spot welds at the rear floor splice with the spot weld remover bit as shown. From there, it was just a matter of carefully prying up the sheet metal edge with a chisel to separate the factory structural glue.
I then made my cuts on the rollbars. Because 1/8” to 3/16” of material will be lost as a result of the cut and subsequent weld gap created, I was careful to mark reference points on either side of the cuts before making the cuts. These reference points will help me later on with the installation of the extension pieces:
Cutting the sides of the tub was tricky. The main roll bar ties into a boxed panel section that is part of the door frame. If we cut anywhere in this area, we weaken the main roll bar tie-in and the door striker attachment point. So that really just leaves us with one place. The interior seam where this boxed rollbar tie-in ends. You can see the seam in the following picture on the driver’s side of the tub (I already drilled some small reference holes at the ends and started cutting with a rotary blade):
Passenger side, already cut along seam:
As you can see on this image, we can only cut 9.5” from the bottom of the belt rail sheet metal bend, along that seam, and then we run into the wheel well hump. This is where things get crafty.
The following image shows the cutting path I took. As shown previously, I cut straight down the belt rail, perpendicular to the top, until I got to the bottom of the belt rail bend. Here, I cut 9.5” along that seam I showed you earlier on the inside and then stopped. Note that until now, our cut has been on the interior side of the wheel well.
From the bottom wheel well flange (hi-lighted in yellow in the image below), I made a straight five-inch cut up to a point, 1” away from the edge of the wheel well. This five inch cut is on the exterior side of the wheel well. I then made another straight cut to the end of my previous cut, also on the exterior side of the wheel well.
The idea is to make these cuts as straight as possible to facilitate the new panel splices.
Next is the matter of completing the rear tub separation by making the final cuts along the wheel well hump.
From the edge of the separated bottom floor panel, I cut straight across to the roll bar tie-in box in the interior of the tub as shown:
To complete the cut on the edge of the raised floor panel, we need to make a cut with a sawzall on the exterior side of the wheel well as shown below. To access this area, I recommend removing the tire or jacking up the frame at the corner to clear the tire (What I did). It will also help tremendously, if you already have a 1” body lift like I did.
To complete the wheel well cut near the exterior face, I had to make one straight cut in the exterior face of the wheel well. Unfortunately, this will also make a horizontal cut on that roll bar tie-in boxed section. Oh well, one more area to repair after separation. To make the last few millimeters, you may need to use a dremel or jigsaw. Notice how I have the cut wheel well flange temporarily clamped out of the way. It would have been a shame to have accidentally cut this off with the sawzall after all the carefull measuring.
After making all our cuts as shown, the only thing holding the wheel well humps to the exterior sheet panel sides is a structural glue. I took a chisel and carefully separated the glue at these joints:
Thanks for the well wishes! I feel like I just opened Pandora's box. All sorts of ideas are popping into my head as to what I can do while the rear of the tub is out of the way. Suddenly, things like outboarding the rear shocks and relocating the upper spring perches become possibilities. That's the thing about modifying Jeeps, you change one thing and a whole series of other unforseen changes follow.
Here is another shot of the removed tub and the resulting cuts on the side of the tub.
I went ahead and cut off the rearmost frame body mounts and ground down the area flat. At this point, my buddy Josh showed up to lend me a much needed hand on the frame build.
For safety’s sake, we went ahead and removed the fuel tank and moved it outside away from the work area (It is very easy to drop the tank once the body is out of the way… it also helps if it is only ¼ full). We did not want to take the chance of blowing up the garage with all the sparks flying once the fuel lines were cut.
Next, we cut the exhaust muffler off (I am replacing my old beat up one), separated the brake lines, e-brake assembly, and cut the fuel lines with a pipe cutter (to avoid sparks with powered tool). Lots of rags will come in handy here.
We then removed all the remaining body mount bolts and carefully raised the body near the frame cut area to give us more clearance (You may need to loosen the fan shroud, we were able to carefully raise the tub just high enough to avoid doing this).
We then drilled some extra ½” plug weld holes. After careful measuring, this is where we decided to make our cut mark:
We are committed now!!!
Note the blue tape pieces on either side of the cut area. There are reference marks on both strips with a measurement written on them. This is very important later on when putting the frame extensions in. We took the original separation distance on the marks and added 15” to verify the proper final dimensions.
Poor Jeep! What have I done!!
We then beveled and squared the exposed edges to prepare them for the frame extensions.
The inserts and extensions required a bit of hammering and some final grinding work to fit them in. At 8” long, we made sure to tack weld one of the plug weld holds on each insert once it was four inches in to avoid slipping.
Note that we had no temporary frame bracing to insure a square fit. In retrospect, we should have tacked on some scrap tube on either sides of the cut, but it turned out that my rear bolted tube bumper already kept things square on the back half and on the front half, things hardly shifted. All in all, everything lined up successfully for reattachment.
Once the proper weld gap spacing and proper dimensions were assured, we took some L2x3 angles and clamped them on to the extensions to insure a straight frame splice.
Plug weld holes filled. She is not going anywhere.
We ran out of daylight and decided this was a good time to stop and have a beer. My buddy Josh was a huge help and I owe him lots of beers for all of his great ideas and expertise in auto work. Sorry his wife will not be too happy with him for being away all day!
Thank you for all the support and encouragement. It's great to share my enthusiasm for this project with other Jeepers.
I took advantage of the long labor day weekend to squeeze some fabrication time in the garage and this is what I have...
Here are my full penetration welds at the splice joints. Just like the AEV Brute frame extension, I made two passes all the way around for all joints.
In preparation for the fish plates, I ground down the welds flat.
These are the fish plates I used on the exterior faces; they reinforce the seam joint connections.
Welding these was no sweat!
The interior plates are designed to overlap the entire length of the extensions (Again, like AEV Brute method). I originally cut these too long and on one end, they clashed with the control arm mounts. I made the proper adjustments and stitch welded them on.
Welding the interior fish plates, especially under the cab, was challenging to say the least. It is tight and hard to see with a welding face shield. I am not going to lie, the passenger side welds are ugly. I will try to clean them up a bit with a grinder before I paint the frame.
I’d like to think, the welds on the driver’s side interior fish plate came out nicer. Lighting made all the difference. Also, I think I am getting better at welding while lying down.
That's all the progress I have thus far. I am going to clean the frame and paint it next. I will then install a 2.5" OME lift and design a new crossmember that will hopefully go with the new Savvy Aluminum Skid plate. Stay tuned!
I painted the frame with Eastwood Extreme Chassis Saver Primer and Satin Black topcoat. Note the blue masking tape area. I still need to weld in the body mounts at these spots. I decided to hold off on these until I decide whether to install them at a raised 1.25” position or my original 1” body lift height. This will all depend on the upcoming tummy tucker cross-member fabrication.
Here is the frame, finally off the jack stands and supporting its own weight…
Time to see how far off the frame alignment is... As far as lengths, we really got it dead on. However, height dimensioning did reveal a careless mistake on our part.
First I took a level across the frame, right behind the rear splice seams of the frame extensions. As you can see, it is pretty level. I then laid the level over the rear body mounts. The bubble skews slightly to the left… just as I feared.
I used the same jack stand as a reference to check alignment of both sides. Here is how the front of the frame compares on the driver’s vs. passenger sides; as expected, no change.
In the following split image, I have the jack by the rear lower control arm mount, note there is hardly any delta between passenger and driver side.
Here is where the problem lies…At the rear bumper corner attachments (By the rear body mounts) there is a 1/2 inch difference passenger and driver side.
I don’t know if the driver’s side is ½” higher or if the passenger side is ½” lower than it should be. I will have to check with an inclinometer and the FSM frame diagrams.
It was really starting to get late when we put the frame back together and we probably rushed this more than we should have. You live you learn, I guess. At this point, I am not sure if it is worth worrying about or if I will need to take it to a shop that has access to a frame straightening machine to correct our goof. The plan right now is to skip the shock outboarding for now, and move on with getting it drivable as is. Sometime before the tub body work begins, I am going to have to address this.