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Discussion Starter · #21 · (Edited)
I'm against the bent links. You are introducing a bending moment into the middle of a link....the absolute worst place to do so. I've seen guys make elaboratly bent and then gussetted links just to get some better ground clearance when changing the capture mounting position would do a much more effective job and give you better strength at the same time.

Let me see if I can dig up some pics of two of my buddies' juggies with bent and gussetted lowers.

Crap....just found out imagestation (or crapstation as I've come to call it) is closing and I can't access my pics on their site. Yippee! :rolleyes:

Sean

***EDIT*** I shouldn't have said "much more effective" without qualifying....it's much more effective to relocate the capture location while still retaining a stronger link. It will not give you as much ground clearance, but if you make your link out of the correct material, dragging it across a rock should cause no more concern than a well built slider. Keep in mind (especially in a rear application) that you don't necessarily have to mount the lower links at or below the center line of the axle tube. If you can get the proper amount of vertical seperation at the axle, you can theoretically mount the lower captures anywhere you want.....you just have to make sure the mounts are beefy since for every inch you go above the centerline of the axle tube, you are greatly increasing the leverage and force on the link and capture mount to resist the axle's propensity to rotate up on acceleration.
 

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Discussion Starter · #22 ·
Short comment on Body Lifts:

For a vehicle as heavy as the FJC's body, I'd probably not recommend one. With hard use, you can actually push the body blocks through the floor leaving a real nightmare to try and fix.

Roger Brown is a gentleman specializing in custom body lift and drivetrain lift kits for Toyotas. 4Crawler Offroad - Custom Body Lift Kits Don't know if he's started working on FJCs, but he sells all sorts of componentry to make a body lift the best it can be.

The advantages of body lifts are more apparent in IFS rigs. If you use a drop bracket style IFS lift, you've often gained not much more than you would have if you'd left it stock suspension wise, and gone with a body lift while raising the bumpers and sliders to match.

The main advantage of a body lift is to clear tires. Another great thing about them is you can do what's called a "drivetrain" lift wherein you make new engine and transmission mounts that effectively raise the entire drivetrain the same amount as the body lift did. There is increased angle on the driveshafts and ujoints, but the main advantage to the drivetrain lift is the fact that you can usually tuck everything in the underbelly high enough to get a flat belly. You will likely also have to raise your gas tank (the exhaust will go up with the engine and you may need to have a new one made or DIY).

The downside is a higher CoG.....but no higher than a regular suspension lift of the same height.

While a body/drivetrain lift is not an option I particularly like, it's one that works well for many people. Just wanted to mention it here for folks that may be considering a drop bracket lift kit or who want to get a flat belly pan.

Quite a bit of fab work is required for this mod. Be forewarned.

HTH,
Sean
 

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I'm one of the guys who has been "bugging" Sean (so apologies -- sorta, but I learn a lot from him).

When looking for a chasis, what are the guidelines (do's and don't) we should consider? For Design strength, material strength, design concept, value, weight, Optimum width 50" or can you squeeze in a couple more inches -- at what cost? Optimum wheel base? COG concerns, etc?

For the sake of the forum members who want to know where I've been looking:
(1) Avalanche Engineering Avalanche Engineering - (970)884-7716 - Extreme 4-wheeling parts and accessories to complete turn key vehicless
(2) Randy Ellis Design Inc. Light Bar Rhino Ford Dodge Chevy Toyota Jeep Truck Accessories
(3) Cambell Enterprises www.campbellent.com
(4) Hendrix Motorsports Home
(5) Spidertrax Spidertrax Off-Road
(6) S&N Fab Inc.S&N Fab

These are the chasis I looked most carefully at. Ultimately what I want to do (I think) is to morph a pre-built chasis such as those above with components of an existing, documented vehicle to retain the "street legal status" of a modified vehicle. I discussed this on another thread and have had conversations with the real experts at the California Highway Patrol and others to better understand how far I can go and still keep the vehicle as a "modified" (therefore fully licensed) vehicle. No need to re-hash it all here.

Thanks Sean. This thread is very helpful to me.
 

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Just a quick interrupt.

Thanks Sean. Your knowledge, experience and opinions are appreciated by many of us here. Thanks for doing this.

Be prepared for a Bellydoc type following of this thread.:lol:
 

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I was just gonna make the exact same Bellydoc joke too.

OK Sean here's one for you.

I need to go LT rear to match my front as you know. You may not know that the obstacle to this for a number of FJ people is that the factory gas tank would be in the way of an LT upper link if it were say, 50% longer or more. One way to solve this is to lose the tank and get a cell but I am getting cheap now. This is what the DR Baja truck does.

Couldn't I bend the link(s) where it would interfere? You mention the problem of introducing a bending moment to the link and I agree that is an issue. But I wonder if the tensile/compressive load on links is really all that much, since they are horizontal. ...?

Reps to you BTW for all that you do for all of us.
 

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Sean, ive talked to you and you are pretty genius when it comes to 4x4. i highly doubt that i would come across any of those trails that often. i think if youre building a wheeler and a daily drive out of the same truck, the FJC is awesome. you kinda get a good taste of both worlds. its especially good if you only offroad one weekend outta the month or so. of course this is all IMO.



Sean you may continue to our originally scheduled progam.
 

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Discussion Starter · #28 ·
I was just gonna make the exact same Bellydoc joke too.

OK Sean here's one for you.

I need to go LT rear to match my front as you know. You may not know that the obstacle to this for a number of FJ people is that the factory gas tank would be in the way of an LT upper link if it were say, 50% longer or more. One way to solve this is to lose the tank and get a cell but I am getting cheap now. This is what the DR Baja truck does.

Couldn't I bend the link(s) where it would interfere? You mention the problem of introducing a bending moment to the link and I agree that is an issue. But I wonder if the tensile/compressive load on links is really all that much, since they are horizontal. ...?

Reps to you BTW for all that you do for all of us.

One question A2A.....what's LT stand for?

That not withstanding....it *sounds* (and correct me if I'm wrong) like you want to keep the factory tank. Not having spent any time under an FJC, I can't really answer your question with regards to the upper link and clearance w/ the gas tank (and/or exhaust). If someone could post a pic of the underbelly (rear portion) of an FJC, I might be able to come up with a suggestion.

If, for some odd reason there is just no way possible to add an upper (which I find hard to believe unless the tank is mounted transversely to the frame rails)....the only real option left is a raidus arm on one side where the upper actually merges into the lower on one side. The only purposes of the upper in that situation would be to control pinion wrap and adjust pinion angle. Your track (panhard) bar would do the side to side locating.

As for load.....most people completely underestimate the forces involved (both compression and tension). In the case of my buggy, the front upper links have 4,135 lbs in compression and the lowers are 6,084 lbs. in tension. So, roughly 2 and 3 tons. That is a LOT of force to place on a link. Putting a bend in the arm will only serve to weaken it and the other problem is that adjustment becomes a problem b/c now you have to phase your SREs with the bend in only 1 specific plane. Since the link will be able to move however many degrees your SRE misalignment spacers allow, you may end up with the bend arcing into the wrong position and hitting something you have to clear in order to make the suspension work.

Let me know what LT stands for and dig up a rear pic and we may be able to come up with something.

Sean
 

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Discussion Starter · #29 ·
i think if youre building a wheeler and a daily drive out of the same truck, the FJC is awesome. you kinda get a good taste of both worlds. its especially good if you only offroad one weekend outta the month or so. of course this is all IMO.
Agreed. The FJC is a great all purpose 4wheeler especially if you need a DD as well.

Sean
 

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Discussion Starter · #30 ·
Just a quick interrupt.

Thanks Sean. Your knowledge, experience and opinions are appreciated by many of us here. Thanks for doing this.

Not a problem. :)

Sean
 

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Man, if anyone ever starts to give you crap in a thread over tech, land use, or reputation... I'm linking them to this thread. That way I can avoid a lengthy, drawn out retort.
 

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One question A2A.....what's LT stand for?
Sean
Long Travel. And Sean I appreciate you're taking the time to help me with these noob questions in your thread.

- I do want to keep the factory tank. It gets in the way of a left upper if you were going to lengthen it.

- You're familiar with Miss FJ's. Jason said that's one way to do it. I just can't find a picture of the third link. I think hers is 45" lowers, and the DR Baja truck is 54" lowers.

- Is it possible to triangulate a 4-link sufficiently so that you could lose the panhard altogether?

- Or is 3-link with a panhard better?
 

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I do want to keep the factory tank. It gets in the way of a left upper if you were going to lengthen it.
Why keep it?

Money aside, you're this far down the road (where have you heard that before?), why not get the Man-a-Fre aux tank and free up that space for suspension. The Man-a-Fre tank holds the same amount of fuel as the stock FJ tank.

You may not want to do it, but I think you should consider it.
 

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Sean...you are a wise young man....maybe I should drop my FJ over to your place so you can bond with it enough to answer the FJ specific questions....and of course feel free to upgrade anything you see fit.....Kurt
 

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Discussion Starter · #36 · (Edited)
I'm one of the guys who has been "bugging" Sean (so apologies -- sorta, but I learn a lot from him).

When looking for a chasis, what are the guidelines (do's and don't) we should consider? For Design strength, material strength, design concept, value, weight, Optimum width 50" or can you squeeze in a couple more inches -- at what cost? Optimum wheel base? COG concerns, etc?

For the sake of the forum members who want to know where I've been looking:
(1) Avalanche Engineering Avalanche Engineering - (970)884-7716 - Extreme 4-wheeling parts and accessories to complete turn key vehicless
(2) Randy Ellis Design Inc. Light Bar Rhino Ford Dodge Chevy Toyota Jeep Truck Accessories
(3) Cambell Enterprises www.campbellent.com
(4) Hendrix Motorsports Home
(5) Spidertrax Spidertrax Off-Road
(6) S&N Fab Inc.S&N Fab

These are the chasis I looked most carefully at. Ultimately what I want to do (I think) is to morph a pre-built chasis such as those above with components of an existing, documented vehicle to retain the "street legal status" of a modified vehicle. I discussed this on another thread and have had conversations with the real experts at the California Highway Patrol and others to better understand how far I can go and still keep the vehicle as a "modified" (therefore fully licensed) vehicle. No need to re-hash it all here.

Thanks Sean. This thread is very helpful to me.

Larry,
You haven't been bugging me at all. But since we last talked, I've gotten two more serious requests for help building/buying a trail rig (not to mention many of the previous ones). I'm just trying to simplify.

One builder I'd HIGHLY recommend you take a look at is: Jason Paule at Twisted Customs.

Twisted Customs - Home

This is a helluva chassis for $4K.....all DOM. You can get all Chromoly for $6800 but IMO, it's not worth doing Chromo as it's harder to weld to and unless you heat treat the entire thing, the extra strength is minimal for the extra cost.


The square tube base framed one also $4K.



Check and make sure Avalanche is still making chassis. I'd heard a rumor that Steve Rumore (Avalanche's owner) was not doing them anymore. Don't know that it's true though. I like the Zero G and Zero G Karnivore personally.

Randy Ellis is a great fabricator, but I've personally never been that fond of any of his chassis. He actually did the best in comp with his tiny samuri that was ultra light weight and very simple....but it wasn't really a custom chassis. That's not to say he can't build a helluva rig, just that I haven't seen a chassis from him I was really impressed by. By contrast, Ian Liljeblad of RPM Fab had a really cool chassis several years back that was super light weight. Wanna say it was called the "yellow jacket". That said, I still don't like it as well as Jason Paule's, Campbell's, Spidertrax's and Avalanche's chassis.

I'm not fond of the X-chassis by Henderson Racing at all. Seems very dull, but if you're looking for a 4 seater, it's a simple, cost effective option.

I've always been impressed with the Spidertrax chassis, but have never priced one out. Your link doesn't appear to give that info either.

As for S&N Fab.....I really like Jason Conover's work. I first met Jason back in 98. Great guy, very knowledgeable. Everyone says it's very strong, but there's just something I don't like about the aesthetics of most of their chassis...can't put my finger on it and would never drop them from consideration for that. You have to choose what you like in terms of the "looks".

One other place you might look into is Shaffer's offroad. Shaffer's Offroad - 775-885-9944

Here's a tube kit to weld to a Jeep frame (starting at $1K):



Seems a little steep for what you get, but if you don't want to mess with bending tube.....

Might fit your street legal requirements pretty easily.

Here's a turn key buggy (1 seater though) for $45K (assuming it's not sold already).



Just the chassis is $3200. (Prices are subject to change due to rising steel cost).


To answer your questions (and this is going to sound a bit like a broken record to an extent)....."it depends".

It depends on what your goals are for the vehicle as to what you should make your chassis out of, what wheelbase you want, how much it will weigh, etc.

Wheeling in Poteau or Disney, Oklahoma requires a very different vehicle than what is required out West. Going to Moab is different than wheeling in AZ. I'll give you my opinions and why b/c that's basically all I can do.

Since you are thinking of possibly competing: weight is a HUGE issue for you. You want it as light as you can get it. The downside to light is durability. You may have trashed the chassis in 3-5 years of hard wheeling and definitely in competition. This has been deemed acceptable by the guys here in AZ that run the really extreme trails and by the folks that compete.

If you compete, 100-105" WB seems to be the hot ticket. By comparison, the trail guys here in AZ will go from as short as 100" all the way to 115" or so. The trend for trail rigs is longer and longer WB b/c the verticals are getting taller and taller. Back East in say, Oklahoma.....125" and even 135" WB is really common b/c they have so many huge ledge descents that they run out there. Problem becomes manueverability at that length though. In AZ, right now, 110" is believed to be the "best" for a trail rig. I think that will soon change to 115" or more. In Moab, I'm of the opinion that short of Area BFE there is no such thing as too long. :lol: The longer WB rigs in Moab routinely spank obstacles the SWB buggies cannot.

Keep in mind there is a VAST divergence between comp rigs and trail rigs now that never existed before. Comp guys are much narrower axled (74" outside of tire to outside of tire is about as wide as you'll ever see a comp rig....b/c they have to make it through the cones) and have much lower CoG. The reason moon buggies have become so popular in the unlimited class is b/c of the steep descents the course builders are setting up as well as the extreme sidehilling. 16-20" belly height is normal. The real advantage to the moon buggy is the low CoG. They actually don't climb as well as a front engine buggy does, but they descend and can sidehill obstacles a front 2 seater cannot. Part of that is b/c the drivetrain is reversed and much of it is b/c the drivetrain rides next to the driver (obviously, these are one seaters for that reason). The overall height of these buggies (mounted on their tires) is usually less than 65". A 2 seater, front engine comp buggy will usually be 72" tall at the most. Comp rigs are also VERY light....some actually have to add weight to make the class spec rules. Usually, they are right at 2400-2600 lbs. 3K-3200 is about the heaviest you'll see.


Trail rigs, by comparison are heavier, taller and wider. And they normally have to be. If they weren't, their extra weight would hang them hopelessly on their belly pans. Outside to outside tire width is as wide as 94" (though most shoot for low to mid 80's to fit the most variety of obstacles). They can range anywhere from 72" tall to 84"....the taller they are, generally the wider the outside tire to outside tire distance. Belly clearance is minimum 20"...and can be just over 30" depending on the vehicle. Typical weights of trail rigs: 3000 for a light one, 5K for a really heavy pig.

As for what works in terms of chassis width: I'd say go as narrow as you possibly can. This is b/c the wider the chassis, the more likely you are to hang up on it on the really hard trails. The more extreme the trail, the narrower you need to be (at least in terms of the chassis width). Most guys I know running 2 seaters are right in the 48-50" width. 55" is a much more comfortable size, but the extra 5" of width may not sound like much, but gets hung up a lot more than the narrower chassis.

As for chassis material....I breifly touched on it before: DOM is my personal choice, but keep in mind that the cost is about double or more of HREW. Chromoly can be about 4 times HREW or 2 times DOM. The real advantage of 4130 Chromoly doesn't come about until you heat treat it though and heat treating an entire chassis is costly and hard to find a place to do it, plus you probably need to anneal the welds before you heat treat (depending on what kind of MIG wire or TIG rod you used to weld it up).

There's nothing wrong with HREW tubing, but it is pretty soft and easily dimples when you roll over. It's also a little more likely to fold in since it's softer than DOM or Chromoly. That can be a good thing though in terms of energy absorption, it just may mean you'll need to splice in new tube after you roll. You can also strengthen it (and make it a lot heavier too unfortunately) by double walling HREW before you bend it.

As for size of tube....again, just like links, the bigger the OD, the stronger the tube (but it may dimple easier since it's got a larger surface area). Personally, unless your chassis is under 3K, I'd say go with 1.75"x.120" wall DOM, or HREW tubing for the main structure. 1.5" ODx.120" wall will work or even 1.5X.250 will work, but the 1 3/4" stuff is just more durable for the long haul. Most comp chassis use 1.5"x.120" wall DOM or Chromoly. Any tube that can be touched by a rock should be .120" wall (unless it's a small tube gussett or something) IMO. Some guys try to get by with .090" wall but it will fail on you if you hit hard enough. IMO, don't risk it.

One word about the lower frame rails.....they'll dimple unless they are either super heavy wall (.250" or thicker) round tube or heavy rectangular wall (.188"). The rectangular tube has some advantages in terms of easy mounting of parts like engine mounts, and flanges for skid plates, tcases, link mounts, etc., but the main advantage is the larger surface area that will be stronger with thinner wall (vs. round heavy walled tube)....though it usually weighs more and looks less "custom". It is by far the most durable. It's also sometimes easier to miter and weld with than trying to bend really heavy walled, large OD'd tubing.

As for CoG on trail rigs....keep it as low as you reasonably can and try and optimize your suspension design so that you can allow your vehicle to sit lower. Of course, there's a certain amount of clearance you'll need at your belly, especially with a 110" or longer WB. I'd say 22-27" is good. Where you want to sit exactly will probably be determined by where your front axle hits your oil pan (if you run a front engine)....unless you go mid engine and go with a well over 90º approach angle.

With the power you plan to run Larry, you can probably get your vehicle to "power" off its belly should you get high centered....you're probably better off shooting for the lower end of belly clearance so you'll be nice an stable.

Again, went through this pretty fast. I'm sure there's stuff I missed or that needs clarification. Please ask if you have questions.

Sean
 

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Discussion Starter · #37 ·
Long Travel. And Sean I appreciate you're taking the time to help me with these noob questions in your thread.

- I do want to keep the factory tank. It gets in the way of a left upper if you were going to lengthen it.

- You're familiar with Miss FJ's. Jason said that's one way to do it. I just can't find a picture of the third link. I think hers is 45" lowers, and the DR Baja truck is 54" lowers.

- Is it possible to triangulate a 4-link sufficiently so that you could lose the panhard altogether?

- Or is 3-link with a panhard better?
Thanks for explaining LT.

I'm gonna agree with Larry and say your best, simplest approach that will give you the most benefit is a fuel cell.

That said though, I'm more of a trail guy....not a high speed desert racer. They build things differently than what I'd build. I've seen stuff on desert trucks that simply wouldn't work for a trail rig b/c they don't work much on an articulation principle but much more on the straight up and down wheel travel. Almost like a dual swing arm on a quad with bypass shocks and coilovers on each arm.

So can someone tell me how the stock FJ is configured in terms of rear links? Is it a 4 link with a panhard? Do the uppers converge on top of the axle or are they like the 3rd Gen 4Runners' 4 links where the lowers are basically straight, and the uppers coverge but are still over a foot and a half between them on the axle and then the run a panhard to locate from side to side?

To answer your question....yes, you can do either a traditional converging upper with straight lower 4 link or dual triangulated 4 link to get rid of the panhard. Problem is.....to do the best one of these (and IMO, the best rear 4link for a TRAIL rig) i.e., the dual triangulated 4 link....you need to SERIOUSLY modify the rear frame....as in cut it off and tube the back end. Unless, you want to try and notch the frame to allow the lowers to travel up into it as the suspension compresses.


Here's a pic of my dual triangulated rear 4 link (before it was totally completed):





Could've sworn I had better pics of this.....don't know where they are. Hopefully you can make out that the two upper links go like this \ / with the wide end at the frame and the narrow end converging on top of the axle. The lowers are wide on the axle and narrow at the frame end. like this: / \

To abbreviate "dual triagulated 4 link" you'll see a lot of guys use this: XX b/c it basically looks like a pair of X's crossing one another from above.

Well, my wife wants me to get off here and grab some lunch, so I gotta run.

Take care guys, and let me know what you come up with in terms of pics of the stock FJ rear.

I'll update more about the 3 link as soon as I get some time.

Sean
 

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Discussion Starter · #38 ·
Sean...you are a wise young man....maybe I should drop my FJ over to your place so you can bond with it enough to answer the FJ specific questions....and of course feel free to upgrade anything you see fit.....Kurt
Drop by anytime. :) Or, hopefully we'll actually get to wheel together soon. ;)

As for me upgrading your FJC.....it took me almost 3 years to build my buggy. I doubt you'd be happy with my pace. :lol:

Sean
 

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Discussion Starter · #39 ·
Man, if anyone ever starts to give you crap in a thread over tech, land use, or reputation... I'm linking them to this thread. That way I can avoid a lengthy, drawn out retort.
Think it'll actually make a difference? :D I'm really good at pushing people's buttons. :lol:

Sean
 

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Discussion Starter · #40 · (Edited)
Long Travel. And Sean I appreciate you're taking the time to help me with these noob questions in your thread.

- I do want to keep the factory tank. It gets in the way of a left upper if you were going to lengthen it.

- You're familiar with Miss FJ's. Jason said that's one way to do it. I just can't find a picture of the third link. I think hers is 45" lowers, and the DR Baja truck is 54" lowers.

- Is it possible to triangulate a 4-link sufficiently so that you could lose the panhard altogether?

- Or is 3-link with a panhard better?

Okay, so back to the 3 link and panhard. My personal opinion is that a 3 link with panhard is a good compromise to a fitment problem. I personally don't care for the way 3 links with panhards work....they move the suspension in an arc dictated by the panhard and for that reason really work the heck out of the panhard and the mounts on both the frame and axle.

This isn't a huge issue....you just have to make sure you beef the mounts really well and use really high quality tubing and SREs....just like losing one of your 4 links is a major problem....a track (panhard) bar is no different.

The main difference is that instead of 4 links on a XX type suspension locating the axle, you have only 1 link (the panhard) doing it. Instead of distributing the load over 4 links, you are concentrating it on one (to an extent....angling the lowers will help take load off the panhard somewhat).

Good things about a 3 link....they usually allow for a lower ride height b/c with only 1 upper, you can get it to go next to the oil pan instead of underneath it. In front axle applications, it's nice b/c they allow you to run more uptravel in the front suspension at a lower ride height b/c you aren't worrying so much about the upper link hitting the engine on full bump compression.

In your case, maybe the 3rd upper link can go next to the driveshaft (DS) on whichever side is opposite your gas tank....maybe between the DS and the exhaust....or, maybe you can move the exhaust over a few inches by remaking it....just enough to run your upper link.

If you can do it this way....this is what I'd suggest.

Your other option is a XX 4 link. This is the best way to do a rear suspension IMO. It spreads the loads out the best and if you build the geometry correctly, you can easily get the rear wheels to track the same as the front even at full droop on one side. Also, no track bar is needed to locate the axle and you don't have the arc of movement you get with a panhard (track) bar.

The problem with this.....you guessed it: fitment. Not only will you need to go to a fuel cell (I don't know what's available from Man-A-Fre), but unless it's super low profile (in which case you'll likely lose capacity) you'll have to end up putting it in the cargo area in the back....and I've never heard of anyone having much luck keeping the fumes under control encased inside the interior.

Then there's the issue of the frame itself.

Here's a better pic of a dual triangulated 4 link (XX):

http://www.pirate4x4.com/forum/attachment.php?attachmentid=323055&stc=1&d=1188518134

Ignore the way the shocks are angled....they are all wrong.

Here's a pic of the rig it's going under....notice the rear frame:



Notice how the frame has been cut off? It's been tubed out and the frame has been raised at more than a 45º angle to allow for the lower links to clear the frame on compression.

If you'll look at my rear frame pic as well, you'll see that after the passenger seating area, it comes up at a decent angle for this same reason. I didn't quite make mine at enough of an angle and ended up having to slightly notch the lower frame (and reinforce, gussett and tube the area) in order to get the last 3/4" of travel out of the suspension.

You have the same options for a XX 4 link. Do one or the other or a combination of both. Regardless of which method you choose....it's a helluvalot of work. :D ....and expense if you can't/don't do it yourself.

Now, all that said, the traditional 4 link where the uppers converge over the diff like this: \ / and the lowers are straight or very slightly angled....usually produce quite a bit of what's referred to as "rear steer" when they articulate. What rear steer really equates to is that b/c the axle is traveling in the arcs determined by the links, when a tire droops on one side, it must necessarily move toward the front of the vehicle. When it compresses on one side, it must move rearward as is dictated by the arc the links travel in. Not only does that tire move forward and aft, but it also moves towards the right or towards the left as the suspension cycles. What this means is that as the rear axle articulates, the wheels may move forward and in slightly....making the rear take a different track than the front....even if the front wheels are pointed straight ahead. This can be very frustrating when trying to pick a line and is why I would rarely recommend a traditional 4 link with converging uppers and straight lowers to anyone. The reason XX 4 links work better is b/c the nature of the geometry can be much more easily made such that you can correct this rear steer by figuring out your roll center angle and getting it close to zero degrees, resulting in a rear suspension that forces the rear tires to follow the fronts.

A panhard 3 link does essentially the same thing, but instead of relying on the geometry of the links to locate the axle, it uses the panhard as the primary means of accomplishing location.

While the XX 4 link is preferable in the rear, most likely I'll be doing a 3 link w/ panhard in the rear of my 4Runner for the same reasons as you. I want to keep the fuel tank under the rig instead of in it, and raising the frame is so much work, I'm not sure it will be worth the extra hassle. Further, while I don't like the stress placed on a panhard, as I said earlier.....if you build it strong enough...It shouldn't matter.

Did that help at all? I'm not sure it did. Some pics of the FJC underbelly would sure help. :)


Sean
 
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