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Goatbuilt 1200 LJ/TJ Chassis Build

58K views 147 replies 42 participants last post by  Wisconsinite 
#1 ·
This is my journey of building my dream jeep. The project is starting off as a 1997 Jeep Wrangler, a Goatbuilt 1200 TJ/LJ Chassis, Fox shocks, Spidertrax axles, and a bunch of other badass parts. I am hoping to have it ready for KOH 2020, that's the goal anyway.

Description of the chassis from the Goatbuilt website:
The concept is to build an all-out no compromise buggy that will use TJ/LJ doors, windshield, Top etc. This will be fully enclosed with functional doors and a top and all the amenities of a TJ jeep.

You will need to cut up a TJ/LJ tub and use the cowl, door surrounds, tub top rail and tail gate surround. You would also use the windshield, tailgate, hood and grill. We have fiberglass cowls, hood and grills available.

Our initial design will be based on an LJ tub length with 110″ wheel base. This uses the same proven suspension geometry with the subframe and all the suspension brackets we use on our Ibex buggy kits. The rear suspension uses 36″ trailing arms for packaging. We plan on making optional rear configurations that are TJ tub length and a comp cut version, but that will not fit a full top.

The main frame is constructed of 2 x 3 x .120 steel tube, the rear fenders are 2 x 2 x .120 tube and the main cage is 2 x .120 DOM tube. The front tubes and other tubes are 1-3/4 x .120 DOM. This will be a full CNC cut and mandrel bent weld it yourself kit, or we can weld it for you.


I started building parts for this chassis while the final design work was taking place, so I have a little bit of catching up to do. Let's start with the rear axle.
 
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#69 · (Edited)
I did some more digging trying to figure out 6l80 VS 4l80. While on paper the 6l80 looks best. It is a little shorter 27.125” VS 29” bell housing to tail shaft or 23.3” VS 26” bell housing to case. It has the lower first 4.03 VS 2.48 and reverse gear 3.06 VS 2.07 with the 6 gear being close to the 4 gear on the 4l80 .67 VS .75 = 90%. The programming is the downfall both in cost and performance. Availability of specific donor years and configurations is another factor depending on what engine and T-case you’re planning on running. Might as well add in 6l90 as a 6l80 alternative since alot of this applies here as well.
The 4l80 while not as glamorous on paper only having 4 gears also makes it simple. No computer. It can run full manual valve body or solenoids and shifter operated. If you’re running a Winters style shifter you can run each position and not have to tap or side shift. Not as critical on year selection, some years are better than others. Cheap to pick up a core and rebuild at desired performance level. Race proven. Reid case available if you have a spare kidney.
Packaging is another determining factor. 4l80/EcoBox/205 is going to be long but doable in a four seat with longer front and rear links. Shorter setups would need to run 4l80/Atlas or 6l80/Atlas or 6l80/205.
While I was able to find positive info about new builds and 6L80’s, I was looking for feedback on running 6L80s. This is a summary of someone who ran a 6l80 and went back to to 4l80.

I wouldn't consider running the 8l90. There is not near enough tech support to get it to interface with a wheeler, and its way to many gears. I currently run a 6l80 with a 2:1 case. This combo gearing wise for trail wheeling is great, but I have a serious love hate relationship with this trans. It has been a tuning nightmare, and in my opinion sucks when it comes to racing. Way to many gears, very slow to respond to tap shift, and it doesn't play nice with the ecm when it comes to racing environment. Last race my 6l80 called it quits. I am getting ready to pull it out and replace it with a 4l80. I have had for different tuners try to get this thing to work, and it has fought us the entire way. I do feel that if you go with a 6l80 you are better off going with a 2012 and newer TCM They are suppose to respond much faster with tap shift.
 
#70 ·
I did some more digging trying to figure out 6l80 VS 4l80. While on paper the 6l80 looks best........The 4l80 while not as glamorous on paper only having 4 gears also makes it simple. No computer. It can run full manual valve body or solenoids and shifter operated. If you’re running a Winters style shifter you can run each position and not have to tap or side shift. Not as critical on year selection, some years are better than others. Cheap to pick up a core and rebuild at desired performance level. Race proven. Reid case available if you have a spare kidney.
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Hydrodynamic, that is kind of what I found also. I don't need anything fancy like a 6l80/90 for this rig, rather something proven and reliable. I talked with my transmission builder, and he is willing to take my 4L60 back and use that as credit on a 4L80. I am very pleased with his customer service, and am going to go that route. Thanks everyone for your input on this.
 
#72 ·
I will try to update this thread in the next day or two. A few nights ago I purchased a junkyard 4L80 that I can use for mock up, then I will bring it in for a rebuild.

To give you a small update quick, a few weeks ago I was part of the FNLC, and I spent way to many hours at the lathe with sandpaper and polish. I put a quick shine on my links. The lowers are 2.25" 7075, and the uppers are 2.00".

As received vs. polishing









Just got word my shocks have shipped! I am trying to schedule a weekend I can have a few of my buddies over and we can make this thing a roller!
 
#79 ·
About time I get this thread updated. Now that both axles are done and about ready to bolt in, I started working on the chassis and subframe.

The subframe is a Goatbuilt part, Part No. 1130. Description from the website:
• Constructed of 3/16 high strength 100KSI yield steel plate, stronger than chromoly and 3 times the strength of the mild steel all the chassis bracket manufacturers use.
• Integrates all 8 chassis suspension link mounts and removable transmission cross-member. All link mounts are made for 2-5/8 width joints with 5/8 bolts
• Includes all 8 5/8 grade 8 link mount bolts, nuts and washers
• All link mounts include weld washers to double up the bolt hole thickness to 3/8″
• Sides are a full 2.5″ Wide x 2.75″ Tall x 3/16 thick section
• Rear is 2.5″ wide x 2.19″ tall section.
• Chassis tubes, engine mounts and skid plates are available separately for a complete base chassis kit
• Comes un-assembled, can be welded for an additional $600
https://goatbuilt.com/product/ibex-universal-chassis-suspension-sub-frame/

I failed at taking pictures of the subframe as it went together, but you get the idea.















 
#85 ·
Hold on a second. Is this the LJ buggy Goatbuilt has been posting pictures of on Instagram for a while?
Could be. But these pictures were taken 7 months ago.

Drew takes care of the Instagram accout. There is a black LJ buggy kit in Colorado he has posted, the one Ian Johnson built (yellow and black), and a few we have built a few for customers.
 
#88 ·
Rear fenders

With the use of the fixture kit, we fit up the rear fender tubes. Material is 2 X 2 X .120 wall.

The mitered joints use a 1/4-20 bolt to keep the tubes flush and secure while tacking. The holes are easily filled during welding.

The holes on the top and inside of the tubes are for interior panels and oval holes are for corner armor.











 
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