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Another TJ-6 Build

64K views 119 replies 35 participants last post by  chop110 
#1 ·
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).

108" TJ. the TJ6 - JeepForum.com

http://www.wranglerforum.com/f118/tj-6-a-63621.html

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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#29 ·
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.
 
#32 ·
Keep us posted, I'm VERY interested in doing this later down the road after I finally buy a Jeep. I was looking at buying an LJ but couldn't drop that much cash so this really caught my eye.
Are there really any downsides to doing this? I know that you're cutting and then welding the frame together but will that weaken the frame? That's really my only worry...
 
#33 ·
I think the frame is much stronger than stock as I have it. So far, the challenge is putting it together withing an acceptable tolerance. You see how I have the back corner off by 1/2". The more I think about, the more I am inclined to live with this and hope that when everything is bolted together, it will line up like it is supposed to.

What is keeping me from finishing this project (besides the lack of free time) is all the other extra stuff I want to do that just happens to be easier when half of the tub is off. Stuff like a new transmission crossmember, SYE, relocating coils, custom rear trackbar bracket, exhaust and cat upgrades, new control arms, etc. This will be a whole new vehicle when I am done with it.
 
#35 ·
I have been out for a while, so I am overdue for some updates.

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.

 
#36 ·
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, 1” x 2” 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.

 
#42 ·
Very nice job! I currently have an LJ and was looking to add a few inches to mine! I know it's an LJ its already long enough! However I have 4 kids that love to go wheeling with me and would love to have a custom Jeep. I was thinking of picking up and extra tub and adding another set of doors! Who knows. I did have one question that I have not see so far and that is what about stretching or extending the soft top, I always wondered about that. Also For my application or idea would it be better just to extend my body aft of the rear wheels? So to jack your thread! And I have subscribed.
 
#47 ·
#46 ·
Good job so far! I turned my CJ-5 into a 6 last year. Stretches are very time consuming projects and it is VERY difficult to get everything lined back up and straight after you cut the frame and the tub. I commend you for attempting the project with the tub still on the frame. With my first attempt I ended up with the rear right corner being a half inch higher than the other four corners. I thought I could live with it, but it eventually drove me nuts and I pulled the whole jeep apart and rebuilt the frame a second time to fix it.

Good job and keep us updated with progress!
 
#48 ·
Have a few questions for you Chop110. Do you think it would of been easier to cut the tub in a straight line just a little further back than where you did? Maybe just in the beginning of the wheel wells and then bolt on body armor could be used so the arch in the wheel well wouldn't have to be fabricated? I hope I'm explaining what I have in my mind correctly. I'm going through the "in my mind" stage right now and I want to have a my ideas ready. I have been looking at an LJ at my local dealer but like you I don't know if I can't justify taking such a loss on my jeep and paying such a price for a 10 year old LJ. Thanks for any insight you or anyone else might have.
 
#49 ·
Well, I guess I am way overdue for an update...

Before I can finish the body work, I need to completely rehaul my drive train. I am currently working on a custom crossmember to go with my Savvy aluminum skid. For vibration isolation, I have chosen to go with AEV's excellent transmission isolation kit from their tummy tucker. The folks at AEV were nice enough to sell it to me by itself.



The isolation kit sits on a 1/4" thick plate which will be welded to a 1" deep by 3" wide box crossmember angled to match skid slopes.







 
#50 ·
Time for painting...



Next is the fabrication of the connection padeyes which will be welded to the interiors of the frame. By previously fitting the skid and interior connection rails underneath the Jeep, I was able to mark the crossmember location on the aluminum skid plate. The passenger side bracket will be welded on the rail while everything sits on a welding table as shown.





The 3/16" plate may be on the thin side when it comes bolt tear out stresses, so I am welding on some additional reinforcement plates on the outside faces.



The driver's side will be fitted and welded in place, while under the Jeep. This is necessary to make sure the bolt holes align.

More to come! :thumb:
 
#53 ·
I am overdue for updates, so here we go…

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



With the skid plate 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 42RE crossmember for the Savvy skid - JeepForum.com
 
#54 ·
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:
:drool:



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...

 
#56 ·
Very nice work!
 
#58 ·
And now comes a little work with Admiral Trackbar (It's a track! ...bar)

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 johhny 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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