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My TJ-6 conversion from a 99 Sahara

35329 Views 50 Replies 10 Participants Last post by  chop110
This project started three years ago and was originally documented in the "Builder's Corner" forum...

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, 'Ziptie' Jason and ‘Kelowna’ Mike).

bctj's 108" TJ. the TJ6

Ziptie's Tj-6 build

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.
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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.

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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.

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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:

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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:

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:

Once I remove the four body mount bolts attaching the tub to the frame, tub separation is achieved:

Here is another shot of the removed tub and the resulting cuts on the side of the tub.

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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!!! :eek:

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.

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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 L2x3x3/8 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!

Anyway, that is what I have so far. The Jeep is still on jacks and it will remain on them until I finish the seam welds at the beveled joints and weld on the fish plates. With the back of the tub off and the fuel tank dropped, new ideas keep popping into my head... outboarding the shocks? Relocate the spring perches? The plan is to eventually go to 35's. Now would be a great time to swap out that D35... If money permits. For now, I am putting in new control arms, a OME 2.5" lift, and an SYE. I can see this taking me a long time to finish.
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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.
Driver’s side:

Passenger’s side:

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.

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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…

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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 drive-able as is. Sometime before the tub body work begins, I am going to have to address this.

Update (Nov 26, 2015): After tightening all of the body bolts, the frame twisted itself back to the correct position; a non-issue after all.
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While I was waiting on parts for my upgraded suspension/drivetrain set up, I took the opportunity to mock up the floor sheet metal section out of cardboard. It will be a single 15” long piece spanning the width of the tub.

Using the cardboard mockup as a template, I proceeded to cut out the floor section from 18 gauge sheet metal. Note that I added some fold tabs to be spot welded during assembly later on.

I have had it in storage for so long that some surface rust has set in. I spent a good amount of time cleaning that out with a rust treatment agent.

Once the part had been sufficiently cleaned, I took it outside and sprayed it with some self etching primer to protect it from any more rusting.

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At this point, the parts I needed to proceed had arrived:
- Savvy aluminum rear upper and lower control arms
- Savvy low profile underarmor aluminum skid plate
- JB SYE kit
- AEV low profile transmission mount kit

I have also installed a 2.5” Old Man Emu coil springs and shock absorbers to the front wheels. I have not done the rear axle as I first want to get my SYE/CV drive shaft combo in while in the tummy tucked location, then I can finally dial in the rear pinion angle with the rear adjustable upper control arms.

I am fabricating my own custom transmission crossmember from some 3/16" thick, 2" x 3" rectangular tube. It will mate up to the Savvy aluminum skid plate allowing for easy maintenance access when the skid plate is removed. Motor vibration will be taken out by the AEV isolator pads tied to the crossmember. I have a basic idea for how all this will work but I need to move things around so that I can produce a proper cardboard mockup.

I chose not to go with the Savvy crossmember as I wanted to weld the bolt tabs to the interior faces of my frame. Also, I think can come up with something that will fit my particular setup better than the Savvy design. The design of the Savvy aluminum skid plate on the other hand is just perfect and I would be hard pressed to try and fab something like that on my own. Hats off to them!

Among the space saving modifications I am making is the replacement of the original, rusty factory cat. You can see it next to the aftermarket replacement on the following picture. Note the lower profile of the aftermarket cat. Every little bit of space is going to count.

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I am overdue for updates, so here we go…

In the interim, I have fabricated a custom crossmember to go with the Savvy aluminum skid.

With the skid on...

If you are interested, a complete build and design description of the crossmember can be found here (Yes, I know I botched the thread title):

My custom 32RH crossmember for the Savvy skid -
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I am chomping at the bit to get back to the actual TJ-6 body stretch, but several things must happen before then...

... Such as axle work! While I was busy with the crossmember, a long awaited component finally arrived. G2 really knows how to put together a Dana44:

I will be outboarding the shocks and shifting back the upper spring perches/buckets. I used a grinder and a dremel with a cut wheel to remove them from the rear frame arches.

Whacked off upper coil buckets. Need some serious cleaning...

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Upper coil perches relocated! Bump stops really line up better.

I also took some time to reverse the rear calipers to make more room for the outboarded lower shock mounts.
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And now comes a little work with Admiral Trackbar (It's a track!

I wanted an adjustable rear track bar with an angled relocation bracket for the different pinion angle of my SYE equipped axle. I also wanted a johnny joint at the axle end of the track bar. However, I did not want to pay +$300 for a Currie setup, which woul have been my next choice. I chose to modify my existing rear track bar as follows:

Welded two halves of a 1/8" thick tube as a sleeve on the factory track bar. I also welded the halves longitudinally along the edges, not just the ends. Ground everything smooth...

Welded 1/4" thick tube sleeve over the new 1/8" material so that a 1 1/4" diameter welded bung would fit in the bigger tube as shown below. Note the setup was sized for a johnny joint.

Finished product next to the original. Painting is next.

Johnny joint = $50
Welded bung = $35
Misc steel tubing = $30

Total comes out to $115. Saved myself around $200. Yay me.
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I fabricated my trackbar mount from scrap 2 x 3 x 3/16" tube I had from my crossmember build...

Here is the bracket welded in place with the track bar attached, ready for clearance testing.

At full bump, the top of the track barely touches the frame crossmember. It should be noted that I have 4" of bumpstops for my rear coils.

If I had an acetalyne torch, I would have heated the rod so I could have bended it a little and thus to improve clearance (Like Unlimited04 did on his setup... incidentally, I got the idea from him). This will be ok for now, I suppose.

Check out the reversed brake calipers courtesy of Mr. Blaine's kit.
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I got my Tom Woods extended drive shaft in. Mine ended up being 32 1/4 inches long.

Installed. Trully a thing of beauty.

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I finally got around to outboarding the rear shocks. I fancy myself to be somewhat of a fabricator. Ha! In the image below, you can see the lower shock mounts being made from square tube. The design is very similar to what can be found in some of the kits out there. I sized mine for the 1/2" pins on the Rancho RS999005 Shocks.

Here is view of the lower mount installed, as well as a chunck of the frame gone (After chopping the frame for the extensions, this didn't faze me in the least) to make room for some Ford shock towers. There are a ton of threads out in the forums that served as go-by's and I am thankful to every one of them.

Speaking of the Ford shock towers... I also have Blaine's handy notch in them. Although in my case, it is more for ease of assembly than weld penetration. With the tub out of the way, I have the luxury of being able to weld all around without obstruction.

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Once the shock mounts are tacked in and the springs are out, I can cycle the shocks from full bump to full extension to check for clearances...

Looks like we clear the installed tire too:

Once I am happy with all tolerances, I finish all of my welds.

I notched a piece of 3/16" angle iron and welded it to the back of the shock towers for strength. In practicality, this is not necessary for most people out there. In my case, there is the possibility that I may have to take my Jeep to a frame straightening machine to fix my 1/2" frame deflection. After taking a chunk out of my frame for the shock outboarding, I didn't want to leave less section modulus at these locations so that they end up being the only spots that do any of the "fix" bending.

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