Chassis swap pondering.....

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Phils67
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Chassis swap pondering.....

Post by Phils67 »

More and more lately I have been thinking about doing a chassis swap. Mostly for the gains of dependability and a more comfortable ride, and the fact my 2020 goal i set 10 years ago to drive my rig cross country is seeming miserably further away. I have always wanted to keep my truck all 'Jeep' in one form or another. Has anyone succesfully done or looked into a JKU body swap with a shortbed pickup? Any builds or writeups?
1967 Gladiator J2000, 1998 4.0L OBD2, T18, D20 twin sticks, D44HD/D60, Detroit lockers, 3.73s, 4wheel disc brake, FSSR, Dakota digital, etc.

Abqwagoneer85
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Re: Chassis swap pondering.....

Post by Abqwagoneer85 »

I have a nice 83 fsj cherokee frame and rolling chassis (axles tires and peeling but nice chrome wagon wheels) that you can arrange to get for next to nothing- I want it outta here for basically beer money. Solid, no rust. PM me if you want it.
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Phils67
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Re: Chassis swap pondering.....

Post by Phils67 »

Where are you located? I HATE the old style frame/suspension i have. I love my truck, but i am so sick of driving a tractor down the street. For here and there use it is ok, but i need more... My 4.0 swap has been painful yet dependable, the engine isnt the issue. Everything around it is the issue. Over a decade of bad build decisions is the issue. Mother nature eating my frame despite non-winter driving in the northeast like it is the last meal on earth is the issue. The frame is puny. The suspension is mediocre. The steering is clunky and horrible. The brakes are poor. The 4wd is the equivilent of buttloving a skid steer in a drunken rage. I have tried creature comforts and upgrades and have spent over 20 grand on an ill-informed build. If i could do it again i would do it a million times differently. Now the thought of doing it that million times differently is becoming a serious consideration.
1967 Gladiator J2000, 1998 4.0L OBD2, T18, D20 twin sticks, D44HD/D60, Detroit lockers, 3.73s, 4wheel disc brake, FSSR, Dakota digital, etc.
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Cecil14
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Re: Chassis swap pondering.....

Post by Cecil14 »

I've been contemplating something similar, but I plan on using a 2005+ F250/350 chassis. The single cab/long box is within a couple inches of a 131" J-truck. Eventually I'd like to switch to airbags all around. I really like the idea of an "all situations" suspension. All it takes is $$$. lol


aa
1983 J-10 - 4.6L(MPFI)/CS130D/Hydroboost/NV3550/D300/44/44/3.54/Disc-Disc/32s/42 gallon 'burb tank
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Phils67
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Re: Chassis swap pondering.....

Post by Phils67 »

Cecil14 wrote:I've been contemplating something similar, but I plan on using a 2005+ F250/350 chassis. The single cab/long box is within a couple inches of a 131" J-truck. Eventually I'd like to switch to airbags all around. I really like the idea of an "all situations" suspension. All it takes is $$$. lol


aa
Exactly. Money.... i considered a 3/4 6.0 gm chassis but i really just like the idea of remaining jeep
1967 Gladiator J2000, 1998 4.0L OBD2, T18, D20 twin sticks, D44HD/D60, Detroit lockers, 3.73s, 4wheel disc brake, FSSR, Dakota digital, etc.
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TurboJ4000
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Re: Chassis swap pondering.....

Post by TurboJ4000 »

I am in the process of the 3/4 ton GM 6.0 chassis swap. The wheelbase is within an inch and I'll get the modern V8, brakes, abs, fuel injection etc. It does feel wrong to be ditching the Jeepness of it and it will never truly be a Jeep again, But, if I was to build the Jeep chassis with a modern Hemi and a 4 link on coilovers up front I would be nearly in the same position at the end from the utility standpoint but be way further in the hole financially. The modern coilover and Hemi will ride nicely have plenty of power and the brakes can be easily improved but other than serious offroading the coilover and long arms would have no benefit and 99.9% of the driving in my truck will be easily handled by the GM for half the cost.

After buying the truck, selling parts and scrapping what was left I have a rolling chassis complete with 6.0 4L80E and manual tcase for less than $1000. You can't even get a Hemi for that money let alone the trans to go with it.
Last edited by TurboJ4000 on Fri Feb 15, 2019 1:33 am, edited 1 time in total.
1970 J4000 / Chevy Frankenstein in progress
Soon to be Lq4 6.0 and 4l80e on 35s
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derf
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Re: Chassis swap pondering.....

Post by derf »

The Wrangler frame and suspension will basically mean you can't do anything heavy duty with the truck. While it will work, it will only be a drive-around-town vehicle. It's not set up for heavy loads or towing. If you're good with that, then I say go for it.

Beyond that, Wranglers are relatively expensive. Finding a good chassis for a reasonable price may be a challenge. But if you're fine spending the money, go for it.

While you're used to 6 cylinder power in your truck, the V6 in the Wranglers, especially the 3.8 in the 2007-11 Wranglers, is disappointing. The 3.6 in the 2012 and newer Wranglers is better but still sub-optimal for a full size truck. Keep in mind also that the 2007-11 Wranglers have the 42RLE automatic transmission which is a warmed over piece of junk with almost no fixes or upgrades. The 5 speed automatic transmission in the 2012 and newer is a much better unit but then you're dealing with the higher prices of the newer Jeeps. The 6 speed manual is basically the same over all the years (2007-present) and it's a good transmission. The long wheelbase LJ Unlimited (2004-06) has the 4.0 which is decent but the same 42RLE automatic. If it has the 5 speed, it's the NV3550 which is a good transmission. The 6 speed will be the same as for the JKs.

You can try to use a short wheelbase Jeep donor but you're going to have to do some serious fabrication to extend the frame. Again, if that's what you are happy doing, go for it.

To me, the 1/2 or 3/4 ton truck makes a lot more sense all around. It's already a truck frame so it's set up for hauling a load in the bed and towing a trailer. But modern trucks ride very comfortably, especially the 1/2 tons. Also, used trucks are dramatically cheaper than Wranglers. Beyond that, you get a V8 and that makes a lot of difference to me. The Chevy trucks have really solid automatic transmissions as well. Ford is good as well. Dodge is hit-or-miss depending on the year. Even a Toyota or Nissan full size truck could be a good donor as well if you want to do something unique.

Don't let me discourage you from running a Wrangler chassis if that's what you really want. It has a lot of upsides to it. And I'm very much of the opinion that people should do their project the way they want. I do a lot of things that would just be easier and cheaper if I did them another way myself. But I go into the project studying every option first before making up my mind. Just look at the alternatives and weight the pros and cons yourself before coming to a decision. Then proceed with confidence.
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Stuka
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Re: Chassis swap pondering.....

Post by Stuka »

A JK frame is WAY stronger than any FSJ frame. Fully boxed frame with lots of cross members. BUT, the coils are a limiting factor for heavy hauling a towing. Which is why the J8 uses leaf springs in back. But, its a 116" wheel base for a JKU, which is too long for a waggy, too short for a J-Truck.

As for the 3.6L in the JK's, it has plenty of power for most use cases. You figure a J20 had a max of 195hp, the 285hp 3.6L is like a rocket ship.

But I would opt for a full size truck frame myself, as the wheel bases match up better, and the are super strong for heavy duty usage.
2017 JKU Rubicon
Pevious Jeeps: 1981 J10, 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ
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derf
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Re: Chassis swap pondering.....

Post by derf »

I was speaking mostly to the suspension, not the frame. It's designed primarily for off roading. And even though it has a 119" wheelbase, it's still only rated to tow 3,500 pounds due in large part to the suspension.

The new Wrangler based pickup will have a longer wheelbase and is rumored to have a much different rear suspension setup (and possibly modified front as well) so that it can get a 6,600 pound tow rating.
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Phils67
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Re: Chassis swap pondering.....

Post by Phils67 »

I hear that about the new pickup also, but i am also not dropping 40k on a new truck just to rip the chassis out of it lol. Maybe 20 years from now....I am dying to see this truck in person though. Supoosedly 4/19 it hits the floors
1967 Gladiator J2000, 1998 4.0L OBD2, T18, D20 twin sticks, D44HD/D60, Detroit lockers, 3.73s, 4wheel disc brake, FSSR, Dakota digital, etc.
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Stuka
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Re: Chassis swap pondering.....

Post by Stuka »

derf wrote:I was speaking mostly to the suspension, not the frame. It's designed primarily for off roading. And even though it has a 119" wheelbase, it's still only rated to tow 3,500 pounds due in large part to the suspension.

The new Wrangler based pickup will have a longer wheelbase and is rumored to have a much different rear suspension setup (and possibly modified front as well) so that it can get a 6,600 pound tow rating.
Yeah, from what I have seen in photos and read, it will basically have Ram 1500 rear suspension. Its still a 4 link with coils, but with a different geometry and multi-rate coils, and a much stiffer sway bar. You can make a JK tow far better if you put a rear sway bar thats about twice as thick as the stock one. You just lose a lot of the off road flexy-ness.

But you should be able to find an early JK rolling chassis for a decent price. They came out 11 years ago, plenty that have rolled, or have flood damage, or similar. I do think it will be easier to put an FSJ body on a JK frame than a pickup, simple because of the proportions. The 2500 series trucks are all setup for big engines and have long noses with giant cabs.
2017 JKU Rubicon
Pevious Jeeps: 1981 J10, 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ

Gottattooz
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Re: Chassis swap pondering.....

Post by Gottattooz »

I bought a 1968 Wagoneer and a 2006 trailblazer ss for this very reason: chassis swap. The plan is to cut out the floor pans and firewall of both vehicles and put the wagoneer body onto the trailblazer chassis. I want to keep the dash and interior of the trailblazer, but wrap it in the wagoneer shell. 6.0l/4l70e all wheel drive with all the bells and whistles. The wheel base of the trailblazer is 3 inches longer, but every other dimension is within an inch. Once i get everything situated and start the swap, I'll start my own build thread.

-Josh
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LMJ20
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Re: Chassis swap pondering.....

Post by LMJ20 »

If one were to swap a FSJ body onto a 2001+ GM chassis. What modifications would need to be made to the engine harness? Would it basically be like setting up the wiring to make the engine run just like it would if you were swapping it into another vehicle.
Also aside from maybie fabing up some body mounts, what other obstacles could we run into?

I have a line on a 2002 Silverado for $300 but with a blown motor. I figure if I’m going to be using the frame, drive train and suspension then I would be hard pressed to find all that for anywhere near $300


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derf
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Re: Chassis swap pondering.....

Post by derf »

The engine harness could probably be left alone. You'd want to find a good place to mount the computer, fuse box, and all the other under hood stuff that's in the vehicle now. And it's probably worthwhile to keep the whole donor fuse box. Having the fuses under the hood makes getting to them much easier than where they are stock in the Wagoneer. But you'd have to spend quite a bit of time splicing wires. You could do a hybrid setup where you wire the key to the donor fuse block and keep the original fuse block intact. You'd just need to make sure the alternator and battery are connected to both fuse blocks. But that's pretty easy. You'd cut off most of the FSJ engine compartment harness as well as cutting off most of the donor's internal chassis wires.

It would be a good idea to get the donor truck's brake booster in the stock FSJ location. That way you can keep the ABS and/or Traction Control from the newer truck. It's probably a matter of fabricating a bracket to mount it correctly, mostly matching the bolt pattern and ensuring you space it correctly from the firewall.

The dash could get interesting as the engine computer may need to talk to the dash. GM was in the process of converting from individual wires to run each gauge to having a CAN bus driving the cluster in the early 2000's. I think 2002 would still have the older individual gauge wires but don't quote me on that. If it does, it's not too hard to wire up each gauge individually with maybe some pull-up resistors to get the gauges to work. If it's a CAN bus system, you maybe could figure out a digital dash. Or just put in your own analog gauge senders to drive the factory FSJ gauges while you tuck the OEM dash out of the way.

The throttle should be a cable to the throttle body. They didn't switch over to throttle by wire until about '04-05. You'd need a custom cable but it may be possible to use the one from the donor truck.

Wheelbase may be off so you'd want to shorten the truck frame to fit under a Waggy. But that's not rocket surgery.

The gas tank filler would be something you'd have to deal with. Plumbing a line from the factory filler location to the GM tank, or even relocating the factory filler isn't too terribly difficult.

If it's an electric shift transfer case, you'll want to either replace it with a manual shift one or you can adapt the switch into a pod under the dash on the Waggy.

Sounds like an interesting project to attempt.
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