CJ6 on JKU frame/suspension - JeepForum.com
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post #1 of 21 Old 08-11-2020, 05:30 PM Thread Starter
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CJ6 on JKU frame/suspension

After wheeling last weekend on a trail that has just gotten horribly rough from use and an increased population of four wheelers in the area it's time to ditch leaf springs. I was with two friends with JKs and they spent a lot of time waiting on us in my CJ, and I was pushing it as fast as I dared without my wife and I losing the fillings in our teeth.

My 75 CJ5 has performed so damn well over the last 27 years, but the body is cracked, the frame has small cracks forming and it's time to tear it down and use the parts on another build. My '63 CJ6 will be the recipient of many of those parts, but I'm seriously thinking about building this thing on a JK frame to get a softer ride. There's a crapton of options in suspension upgrades for these, from mild to wild and the strength is undeniably much better than any CJ frame.

I know that I could build a link suspension on the CJ6 frame (it's actually a factory boxed 73 Commando frame with CJ body and suspension mounts), but the width (or lack of) does make that very challenging to get a well working four link. I really don't want to spend the money on link components and coil overs to compromise their mounting positions and potential performance because the frame is so narrow.

I know that one of the magazines did this a few years ago and that build was slapped together. They cut the crap out of the tub to mount it as low on the frame as possible. I'd rather not do that.

I'll be looking at a JK frame in a couple of days that is supposed to have been modified for the wheelbase of an FC170 (103"). This might fit the bill, though I still haven't been given a price on it. Apparently the owner is a widow selling unfinished project parts her husband had. My contact to her is through someone helping her.

Has anyone seen documentation on the web of something similar? I've found very little on the web, other than people considering JKU frames under FSJs and one thread on a CJ8. Nothing beyond what I'm doing here as well, considering the possibility.

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post #2 of 21 Old 08-11-2020, 06:47 PM
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With the right tools and skill anything can be made to work.


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post #3 of 21 Old 08-11-2020, 08:50 PM
StoneTower
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I think TDK makes hybrid frames that take TJ suspension parts for CJ models. I know they make CJ6 frames. They are expensive, but so it time as you get older.
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post #4 of 21 Old 08-11-2020, 10:43 PM
only in a jeep cj
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If your wanting to keep the tub whole, I would think an LJ frame would be a better size match.

You will get the 104" wheelbase (72 to 75 CJ6 and the Scramblers are this), it will be wider, coils or coil overs, plenty strong enough, and you can run any LJ based stock or custom suspension....unless 104 or a stretch out to say 120 or so is not enough.
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Ed
1975 CJ-6 1983 CJ-8
1986 CJ-7 Laredo 1986 2003 Inca Gold TJ Rubicon
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post #5 of 21 Old 08-12-2020, 04:47 AM
bob4703
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With the right tools and skill anything can be made to work.
and money!

-----

Paved roads are prime examples of government over spending!
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post #6 of 21 Old 08-12-2020, 06:55 AM
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and money!
Of course! If you need anything custom made and I can be a help just holler.


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post #7 of 21 Old 08-12-2020, 07:49 AM
John Strenk
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You know...
Those JK's were probably happy you were slowing things down otherwise they might start overheating...
Just saying....
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post #8 of 21 Old 08-12-2020, 11:25 AM
Fourtrail
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Following, the frame under my '6 is looking a little worse for wear and it is going to need to be replaced in the near future. I was planning to do TDK frame rails and put in crossmembers where I needed them and set the frame rail width to match the leaf spring perches on the front axle so I don't have to outboard anymore. interested in going to links and coilovers but not sure how soon the jeep funds are going to cover that. this time the jeep will hopefully sit lower as I am no longer afraid to cut the tub floor to try and get a flat belly with the np435/203.

80 CJ-5, 74 CJ-6, 56 CJ-5
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post #9 of 21 Old 08-12-2020, 11:35 AM Thread Starter
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Originally Posted by only in a jeep cj View Post
If your wanting to keep the tub whole, I would think an LJ frame would be a better size match.

You will get the 104" wheelbase (72 to 75 CJ6 and the Scramblers are this), it will be wider, coils or coil overs, plenty strong enough, and you can run any LJ based stock or custom suspension....unless 104 or a stretch out to say 120 or so is not enough.
I've considered this, but finding an LJ frame is difficult. Finding one that isn't at a price approaching (usually exceeding) a new frame from TDK is next to impossible.

It's relatively east to reduce the wheelbase on the JKU frame. They have a front half and a back half that is a slip fit joint where they come together. Cut the welds, press the two halves apart and cut out what you don't want and slide/weld it back together. The rails are parallel to each other in this area, so that takes most of the brain damage out of it. The attached photos are from Fourwheeler magazine's project. The frame I'm looking at has already been modified to the desired wheelbase I'm told. A tape measure will be going along to verify.

I'm honestly looking to see if anyone has seen anything documented on this. The fabrication is the easy part. I'm trying to see if there are lessons learned out there on the web already. If not, I'll learn them myself.
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post #10 of 21 Old 08-12-2020, 11:45 AM Thread Starter
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Following, the frame under my '6 is looking a little worse for wear and it is going to need to be replaced in the near future.
If this works out I will be selling the 73 Commando frame that's under my '6 currently. I cut the Commando body/suspension mounts off of it and bolted on mounts from a '72 CJ5 frame that I had. The bolt (rivet holes really) were already there since the '6 and Commando of any given year had basically the same frame rails (you probably know this already). The Commando rails are longer and boxed forward of the crossmember that's above the rear pinion. I chose this frame because the original frame was completely hacked up and it made it possible to use the longer AMC front clip and the AMC 401 I had. I never completed this build, so it's mostly bare steel as I did have it blasted. The dry climate here has kept even flash rust at bay.
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post #11 of 21 Old 08-12-2020, 01:52 PM
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If this works out I will be selling the 73 Commando frame that's under my '6 currently. I cut the Commando body/suspension mounts off of it and bolted on mounts from a '72 CJ5 frame that I had. The bolt (rivet holes really) were already there since the '6 and Commando of any given year had basically the same frame rails (you probably know this already). The Commando rails are longer and boxed forward of the crossmember that's above the rear pinion. I chose this frame because the original frame was completely hacked up and it made it possible to use the longer AMC front clip and the AMC 401 I had. I never completed this build, so it's mostly bare steel as I did have it blasted. The dry climate here has kept even flash rust at bay.



need to go to something heavier duty than even the commando frame. The 42's bolted to dana 60's and v-8 power would do in the commando frame just like the factory '6 frame. I have boxed it back to the start of the rear wheel arch and still get enough frame flex that it was ripping the rollbar mounts off of the frame. ended up having to bushing mount the cage to stop that problem. also need to beef up the front as I was pulling the splined ujoints off of the steering box when it flexed.
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post #12 of 21 Old 08-12-2020, 08:29 PM
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I don't know what shipping would be like, but Davey's Jeeps in Ohio here seemed to have a lot of LJ frames when I was browsing thru their inventory last month...



TDK - it will be the last frame needed for that Jeep. SOLID!

Rick

1978 CJ5 5.0HO/T177/D300, '86 D30/D44 WT axles, 'glass body, 31x10.5 BFG A/T, TDK galv'd frame - DD and weekend toy


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post #13 of 21 Old 08-14-2020, 12:52 PM Thread Starter
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JK frame with 13" taken out of it has been purchased and it came with all of the links, stock JK springs some other suspension parts and the hardware to attach everything. Got a JK steering box too. It was never used under a vehicle, so it's in primo condition and the guy did a great job of jigging it for the cut and weld job. I'm probably going to go back and pick up an L33 LS engine and an NV4500. The widow thought that she would never be able to find a buyer for the frame because of the customization done to it, so it worked out well for both of us.

It will be a while before this gets underway as we're about to embark on adding on to our house, but I'm glad to have a base to measure off of and plan. The time will give me an opportunity to explore all of the suspension offerings that are out there for the JK, and there are LOT. That's the main reason I chose to go this route vs TDK or an LJ frame. I got all of the parts for 1/5 of the starting price of a TDK frame too.
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post #14 of 21 Old 08-15-2020, 09:01 PM
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Nice! Now, as you piece it together, you can make a rolling chassis to install when it is together and running. Unbolt body, lift, roll old out, roll new in, connect brake lines to master cyl, clutch links, steering column to box, bolt body on, connect gauges/powers/grounds and drive off!

Rick

1978 CJ5 5.0HO/T177/D300, '86 D30/D44 WT axles, 'glass body, 31x10.5 BFG A/T, TDK galv'd frame - DD and weekend toy


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post #15 of 21 Old 08-16-2020, 11:53 AM
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Hoss

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