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Discussion Starter · #1 ·
Despite how capable trucks and truck based SUV's are offroad, you can always tell it has a solid rear axle by how much it jitters offroad. Its especially evident with washboard surfaces. My 93 dakota rides fairly nice the front is soft and squishy (a little too soft after 325K on the torsion bars if you ask me), even though the rear suspension is still fairly soft its a bit harsh when it finds washboards. Other than airing down, there isnt much you can realistically do to help with washboard roads with a solid axle.Sure more speed can help but its not always possible. Ive driven enough subarus and other cars with independent suspension at all four corners to know how much more stable and planted they are with washboards.Those are cars for the most part. They are unibody and they typically dont have low range. I'm just wondering if there is a vehicle that is a proper 4x4 vehicle stateside that has IFS/IRS and a true honest to god 2 speed transfer case and preferably a frame. Ive driven a fiat cherokee and it was much stiffer riding than I would like for offroad use, and its "transfer case" was just a CVT with some lower preset gears, nothing mechanically splitting engine torque to all 4 wheels...
 

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The Cherokee does not have a CVT transmission.

You won't find a "heavy duty" type of 4WD system with IFS, much less IRS, regardless of the marketing nonsense. They reasons the auto makers have for using IFS and IRS are not off road performance, but cost, handling and a few safety factors. The only thing I can think of with independent suspension that is built "heavy" are off road racing vehicles, and heavy military vehicles like HMMWV, MRAPs, the MTVR and various MAN and Tatra trucks from Europe. The HMMWV and it's H1 civilian model are about as close as you will get to a normal sized vehicle you can just sit in and go with independent suspension with a bit of beef to it and even they are no where near bulletproof and are known to have a lot of issues with the axle shafts, joints and portals breaking.
 

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Discussion Starter · #3 ·
I'm not claiming IFS/IRS is for serious offroad use, but unless I am driving over boulders the size of VW's (or actual VW's for that matter) then I don't want to crawl along in the single digits. Most of my offroading these days is driving down rough. "unimproved", or "primitive" roads at 20-40 MPH. A solid axle is great when articulation is required but independent suspension is king in that environment especially after you free up the suspension by tossing the swaybar to the scrap pile. Besides what is so wrong about wanting handling and ride comfort when bombing down fire roads? Most of what I said doesnt require low range but those roads still might have sections that are heavily rutted/rocky and a slower approach may be needed.
 

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You want a vehicle with IFS/IRS for a smooth ride on bumpy roads?.....buy a RZR, I love mine. (yeah, probably not the answer you seek).
 

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...what is so wrong about wanting handling and ride comfort when bombing down fire roads?
not a thing wrong with it at all :) - one way I have improved the ride of my leaf-spring trucks has been to 1) install longer leafs, and 2) 'fine tune' the number of leafs so that the truck is nicely 'in' the leaf spring and not 'on' the leaf spring - IOW, with normal weight on wheels, the truck is settled into the leafs and the leafs have sprung down a bit at normal ride height - which often involves relocating the rear shackle mounts and/or different shackles to get the ride height just right. To help explain 'in' vs 'on' the leafs - push down on the rear bumper and the back half of the truck actually has some 'spring' in the suspension...vs say an old school 1-ton that if you push down on the rear bumper and there's no squish and you throw out your back in the attempt.

It's the same principle as how a pickup always has a nicer ride when loaded with 1000 lbs of rock or lumber or has a camper on back. Set up the suspension so it 'acts' the same but without the 1000 lbs in the bed and you'll have a real nice ride, certainly much better than the stock 52" Mopar leafs.

Nice long leafs in back, like the 63" Chevy's for example, provide a nice ride while also holding the weight - nice and springy. But...and there's always a con - the more springy the leafs are can also negatively affect the weight-carrying capacity (new trucks make up for this by having OE air bags that can be pumped up to augment for heavy loads. Also, removing a leaf or two to get a nice ride can also induce increased axle wrap.

My recommendation - get a set of Procomp 63" leafs (#13211 is a 3.5" lift spring, 13711 is 5.5" lift - might be able to remove the block), make the necessary frame mode for the mount mods, and you'll have nice gains in ride quality.

And...when we really wanna get jiggy on the dirt roads we often times air down from 35 to about 20 psi, and that really helps (y)

- Sam
 
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Discussion Starter · #6 ·
the 63" springs sounds like a decent option but wont the rear end still hop sideways when ever it finds washboards, partially in the middle of a turn? My 96 ram 1500 is 2wd and it desperately needs softer springs out back because even with a toolbox full of recovery gear and 2 full size spares out back it doesnt have enough squish in the rear suspension...
 

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well sure it'll still hop sideways...but I'd also say that 'everything' will hop sideways - maybe not under the exact same circumstances, but I cannot imagine IRS will completely eliminate all hop... - I guess it all depends on how much hop is too much...and adjust from there..?
 

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Discussion Starter · #8 · (Edited)
well, when I say it hops sideways whenever a rear wheel hits a bump I mean it HOPS sideways. At the speeds I drive when that happens the rear end swings for the fence a good 2-3 ft and it completely removes any and all rear end grip which is a serious problem for a 2wd truck and a minor nuisance with a 4wd truck in 4wd. By comparison my 84 300ZX at much faster speeds over washboards is much more planted and stable. Hitting a bump with one of the rear tires doesnt induce a slide or hopping. When it does slide its much more progressive and easier to catch, even when everything happens much quicker due to the shorter wheelbase. Also because you dont loose all traction it still propells you through the turn. I know I'm comparing a sports car to a truck but every vehicle I've driven off pavement with a solid rear axle behaves the same including my friend's old and wore the phuck out 2wd kawasaki bayou...granted for the bayou sideways through a turn was the name of the game because the brakes didnt really work and it was so wore out the suspension gemoetry got a bit strange if you tried to turn normally, and just hope to hell the 220cc engine didnt run out of HP in the middle of the turn..
 

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Learn to drift. 😁
 
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...well...if you're really wanting an 'off-road capable pickup truck' that has IFS/IRS...maybe consider a Subaru Baja. Honestly, I have a mild craving to get a nice one, do a mild lift, toss on some nice ATs, and enjoy the hell out of it...
 
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Discussion Starter · #11 ·
no low range. That and for whatever reason working on subarus pisses me the hell off. I don't normally throw tools, but when working on a subaru...
 

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there are 2 types of units built FOR off road , used in competition by the ultra 4 folks . they had been all solid axle units , but have been changing to independent front and rear axles . ultra 4 racing on the web will SHOW you both types in very hard use with high HP engines .
 

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Discussion Starter · #13 ·
I know of the ultra 4 IFS/IRS but paying 20-30K for a diff really inst in the cards right now.
 

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Discussion Starter · #14 ·
In the spirit of the original question it seems 2004-2011 fraud exploders use IRS,and are body on frame,and have a 2 speed transfer case.Anyone know of anything else that is not a FMC product?
 

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Discussion Starter · #15 ·
2011+ jeep grand chekoees have IRS, but full time 4wd, and unibodies..
 

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You want a vehicle with IFS/IRS for a smooth ride on bumpy roads?.....buy a RZR, I love mine. (yeah, probably not the answer you seek).
howdy dude , where the frigg did you come from , aint seen yer ass in a dogs age , matter of fact l think the dog died , howya been
 

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+1 on airing down the tires. 20-30 psi instead of 80 on 1ton truck is an amazing difference.

Did any of the Ford Explorers with IRS (the first ones) come with 4Lo? Not recommending per se, just they may have had that combination.
 

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dodge dakota 4x4 had ifs .... the diff was bolted hard to truck ..
 

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Not so much the independent suspension that helps, but the unsprung weight. To follow the washboard roads, the wheels, brakes, axle parts, all need to change direction fast. The less those parts weigh, the faster they can react.Yea, springs and shocks can help,but will only make a tiny difference.

Think light weight wheels, passenger tires, in a smaller & narrower size, disk brakes, light axle.

Or independent, take guidance from the race trucks, and hummer. Go inboard brakes, again, light weight wheels & tires, light weight arms, and knuckles.

Google unsprung weight. Or just slow down.
 
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