Comanche Fun Runner Phase 3

Comanche_SS

Comanche_SS

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Joined
May 13, 2026
Member Number
10195
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13
New around here, but got an old build I am working on.

A little backstory, the truck was bought from the Original Owner in 2018. Its a 1989 Jeep Comanche, Originally I6, 4x4, 5 Speed. Socal Rust free truck.

Phase 1 when I bought it was a little budget lift and the fiberglass. (poor college kid era)
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Phase 2 was LS swap, beams, coilovers, etc. (first big fabrication, engine swap project)

It originally had a Supercharged 5.3/4L80E and I beams.

It currently has TTB's, an LS3, AX15, NP242, Fabbed full float 9".

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Phase 3 Originally was supposed to be just a backhalf, maybe a trans swap, and just cruise it safely without a cage, light off-roading.
But thats the gist of where we are today. IIll elaborate on the future plans in the next post.

If you want to see from day 1, up to today's progress in the old thread see that here:
Comanche Fun-Runner: LS3, Ford D44 TTB IFS, AX-15/NP242, Built Ford 9’’
 
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I admittedly did some things during phase 2 that I thought were okay at the time, only to form disdain for those things as time progressed. I dont like the engine mounts, shock towers, transmission, wiring, or original sheet metal front half. So phase 3 is getting re-defined.

A little background on me, I am a mechanical Engineer by education, and electrical engineer by career, and an ex-certified welder (welding is the backup career if **** hits the fan)

I have designed chassis and suspension in the past, in seperate scenarios/instances. My long time goal was to design a ground up chassis/suspension car for my myself. I posses the skills, but never have had enough time to sit down to do it. Well, life circumstances have changed for better or worse and right now I have plenty of time to work on the design.

The goal/plan here is to use many of the parts on the truck already, and drop the cab into a tube chassis build. The only reason the cab is included is because it is already registered & insured at a determined value I get to set. And I want this to be street legal. The truck is also my first date/wedding vehicle with my wife so its pretty sentimental.

The parts I will be using in the full chassis build: (keep in mind I am using these as they are already owned or part of the truck)
-Cab (already have)
-LS3 (already have)
-4L80E or 8HP
-tcase undecided
-Full float 9" rear (already have)
-D44 TTB (already have) (dont mention typical IFS, I cant afford it, already thought about it)
-Method Beadlocks w/35'' tires (already have)

There will be no bed, no front clip. Think Street legal truggy. Will be using Ultra4 safety & spec guidelines. The entire car will be designed in 3D CAD.

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mobil1syn said:
where you located?

type of wheeling?
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Im in the Midwest.

I want it to be able to do anything decently well. Willing to compromise on extreme scenario performance for better overall performance. I come from a Desert high speed background, but where I live now is bouncer/Ultra4 country.
 
Got some time to spend on getting the foundation begun.

Going into it, I knew trying to use the Jeep Floor was going to be more hassle than its worth, so thinking that tje cab will be mounted thru the rockers, ill cut out everything else between the rockers. looking like I will need a sub floor, and then a belly area for drivetrain/suspension.

Its worth noting, I dont plan for any bends in the cage, although most of the cab cage area will require rolled portions on the tubes.

Typical 2x6x3/16 rockers, tubing is all 1.75x.120 per 4400 guidebook.

Trying to achieve a Cross and an "X" in all planes of the cab cage. I will field fit some radius corner gussets around the windshield bars.

Once I get the cab cage done and how I like it, I can focus on the rest of the chassis. Still need to decide if I am cutting the firewall out or using the factory one. Other than it sticking out a bit far, I dont mind it. I intend to use the brakes, steering, and pedal assembly I already have, so it seems redundant to remove the firewall, also having working wipers would be a nice luxury.

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Why no bed sides? Seems as though you already have the fiberglass sides, why not use them?

Sick build, Im looking forward to more updates as things progress.
 
SLOWPOKE693 said:
Why no bed sides? Seems as though you already have the fiberglass sides, why not use them?

Sick build, Im looking forward to more updates as things progress.
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I will probably keep them around as an accessory and maybe build some quick attachments for them when going to shows or dirt/sand/mud parks. But as far as the function vs form of them, they will be in the way when off roading and likely destroyed.
 
Intentions of racing or ultra4 style? While not obsolete yet for U4, you’re building yourself into a corner with 1.75” -otherwise party on

Building mine with 1.75 seemed like a good idea until all the roll cage Karen’s discovered they had a voice. Pretty much lost interest in returning because of that.
 
WiscoF100 said:
Intentions of racing or ultra4 style? While not obsolete yet for U4, you’re building yourself into a corner with 1.75” -otherwise party on

Building mine with 1.75 seemed like a good idea until all the roll cage Karen’s discovered they had a voice. Pretty much lost interest in returning because of that.
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Not intending to compete, I cant afford that lol.

I mostly mention the U4 guidelines for safety and build/design practice. Id rather rely on a proven safety factor specification than nothing at all when designing something. I am sure I could build something quite interesting and unique without any rules, but it may not be safe or practical. With the type of speed and terrain I want this truck to be able to do, I cant ignore that it needs to be safe, U4 guidelines have helped many drivers and cars survive some pretty spectacular things.
 
I realize I never really showed photos of the current state and what brought me here.

I started working on some things that needed repair/modification and my years of frustration with the original metal & proportions finally boiled over and here we are designing a full chassis lol.

Hopefully you can tell from these photos and my designs posted above that I am setting the cab and engine back quite a bit. Not sure exactly how much yet, still to be determined. But the TTB Centerline is currently directly under cylinder 3 & 4, and the cab is right up behind the engine.

The wheelbase I am currently showing in my designs is 125" but Im not married to that either at this point. I need to show some 48'' trailing arms and see where I can mount them to really nail down the rear wheel axis CL.
 

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mobil1syn said:
out of curiosity, why an exo cage?
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Couple reasons, if youve never sat in a Comanche, there is very limited room in there as it is!

I like the stock dash shell, and want to keep it.

I plan to wheel this truck in places it could roll regularly...and dont want to replace the cab regularly.

Also, with it being a road going vehicle, I want to use DOT seatbelts, not necessarily harnesses (at least not when just cruising) and similarly, I dont want to have to wear a helmet when just cruising as you should always do with a cage right beside your noggin.
 
Started to get into the rear link geometry this evening. This is just the start so dont get on my case lol, this isnt something I want/plan to figure out in one sitting lol. This is definitely more focused on going fast, and speed comfortability vs crawling. That may change still, im still pondering on all of this.

Alright, basis of design is 35-37'' tires, 125'' wheelbase, 21'' belly height.
  • Upper links
    • Chassis mount separation: 30"
    • Axle separation: 3.75"
    • Chassis mount height: 27"
    • Axle Mount Height 26.5''
    • Length: 40"
  • Lower links
    • Chassis mount separation: 45.375"
    • Axle separation: 45.375"
    • Chassis mount height 21''
    • Axle mount height: 17.5"
    • Length: 48"
This nets a ~70% anti squat, Roughly 1.5'' Driveshaft plunge, and should net easily over 20'' of travel with a typical 75% motion ratio trailing arm.

The only thing I may change is the upper chassis separation, as it is the upper links have low authority over the lateral motion of the axle, but a ton of rotational control. I can probably find a happier medium with those two characteristics so that I have better side load strength on the axle assembly.

The good news is this looks super packagable, sub floor will be basically the same plane from oil pan to lower link mounts. Driveshaft will be protected. Looking like no problems there. This is a nice change compared to years of trying to package things around the stock sheet metal.

I wanted a little win so I went ahead and started designing the axle lower link mounts, might do some sort of outer bracing as well. we will see.


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Not doing a ton of design tonight, but still twiddling away on things. Really trying to decide how low I want the belly skid plate, Its looking like 5-5.5'' below the bottom of rocker will be the bottom of the skid plate. That still gets the skid an inch or two above axle CL, but keeps the engine and trans out of the cab too much.

Kind of hoping some will chime in on this part, keep in mind this is a small truck and I dont have much room to spare, so every inch of interior cab space will be important. Having a LCOG is always a plus too, as long as I dont lose ground clearance.

Skid plate height is around 19'', rocker height is around 25''

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Been busy starting to strip and sell not needed parts off the truck.

Going to strip it to a point where I can cut off the frame rails behind the cab, to then stand the cab up with the back wall on the ground. Will make it much easier to get the cab detached from the frame while I can work vertically instead of laying under the truck. My Back will appreciate it lol

Pretty much the only thing from the existing back half of the truck that Ill be keeping is the tailgate, one day ill incorporate it onto the truck somehow.

Back glass, bed carcass, bedises, tail lights, back frame section and whatever else will be gone.

Still leaning towards cutting the floor out of the cab as well, but going to keep thinking on that one once I can tip the cab up and get a good look and measurements from it.

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