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Building a 70mph rock crawler.

Tony_SS

Tony_SS

NAXJA Supporting Vendor
Location
Washington MO
Suspension gurus, how would you tackle this challenge? I come from the pro-touring world in which cars are built to do all things well. With that in mind, I would like to build my XJ with the ability to run a straight, smooth 70 mph down the highway, arrive at the trail and be able to tackle "somewhat" challenging terrain.

If I had to lean to one side, it would be toward the ability to cruise 70, but I don't want to sacrifice being able crawl through a rough creek bed etc.

I live in the midwest, so our terrain is wooded, creeks, streams, hills, grass, rock, dirt and mud.

So, what set up, parts, etc would you use to achieve this type of build?
 
Buy quality tires and keep them balanced.

use appropriate axle gears.

Any properly built jeep should have no problem crawling moderate to difficult rocks and driving home at 70 mph afterward.
 
cal said:
Buy quality tires and keep them balanced.

use appropriate axle gears.

Any properly built jeep should have no problem crawling moderate to difficult rocks and driving home at 70 mph afterward.
Click to expand...

That pretty much sums it up.
 
To tackle "somewhat" challenging terrain, just add skidplates to the gas tank & transfer case, use ZJ steering tie rod, get recovery points & go for it.
Or add a 2" lift and 30 or 31" tires. In the midwest, you may not really need gears.

Going bigger... Rough Country can sell you a 4.5" lift & control arm drop brackets, gear to 4.56, & put some 33" tires on it.

More expensive... Full Traction (and lots of others) make long arm kits that will smooth out the ride & crawl nicely.

Spend your money on good tires & shocks, though - just like pro touring, these items make a lot of difference.
What are your other projects?
 
Round, balanced tires are key. Other than that, build the rest of the rig with quality components and there is really no reason it can't cruise down the highway all day long. Every xj I owned was on 3/4 tons, driven several hours to go wheeling, tackled some pretty difficult trails, drove home, and then to work the next day.
 
Tony,
More people on NAXJA run daily driver/weekend wheeler rigs than caged out trail-only rigs, so you should have no problem finding comparables to assist you with how you want to build your rig.

There are many build threads here which highlight rigs capable of running moderate to "expert" rated trails and still handle daily driving with ease. I can comfortably drive my rig to and from the trails at 75-80mph (yes, we have 80mph legal limits in rural Utah!) and wheel for a week on challenging trails and explore remote regions, fully confident in the reliability of my rig.

IMG_4328_zps92cc3308.jpg



IMG_8522_zpsd636ba18.jpg


Here's my build thread link http://www.naxja.org/forum/showthread.php?t=913774&page=2

Here's a few more rigs, most which fit your criteria of "70MPH capable" and still handle trail duties with ease. Component lists should help you as well.

http://www.naxja.org/forum/showthread.php?t=1106311
http://www.naxja.org/forum/showthread.php?t=1098576
http://www.naxja.org/forum/showthread.php?t=1052001

Figure out what size tire you want to run to handle the trails your plan to tackle and then add the minimum amount of suspension lift to accomodate tire clearance when the suspension cycles. Bumpstop to maintain tire to fender clearance and run quality springs/shocks and tires which balance well.
Hope this info helps.
 
Last edited:
of course the things stated above. but my good freeway handling came from the proper arm angle of long arms and the fact that I could finally get a good castor angle. then good steering
I was always able to go 70mph with regular old mud tires and 4.56 gears. but as soon as you hit a pot hole or bad bump with stock steering and short arms, goodbye handling!
 
Good point, 4-4.5" of lift seems to be the magic number to still allow for the proper balance of caster VS front driveline angle, in order to keep vibrations at a minimum and still have the rig steer properly at freeway speeds. Not everyone will want to go through the effort to rotate their knuckles as I did, to allow for more lift and still have the ability to tune caster for driveability.
 
Thank you all for the info thus far. I need to research different suspension setups, ie. long arms, etc.

Here is my current build thread
http://www.naxja.org/forum/showthread.php?t=1106984

I'm at about a 3" lift. Front springs and AAL. No other lift mods. I do have an SYE. Brand new 31" Cooper AT3's. Alignment is pretty good, with 6º caster IIRC. But driving home last night, was twitchy and bouncy going down the road at 65mph. I was under the impression that if my alignment setting were spot on, the ride would be controllable. I guess I need to replace some original front end parts, and upgrade where needed.

This weekend I'm putting in an RE track bar which will replace the original 155k one. And from there I'm going to replace all other tie rods to try and tighten up the steering as well.

Thanks all for the direction so far.
 
i'm on 37's and 1 ton axles and i daily drive mine, 80-90mph on the highway daily. no problems. Like Cal said, as long as it's built right....
 
Judging by the other posts in this thread, it will be important that you start with a silver XJ.
i.php

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We drove from Maine to Utah (at ~70), played around for a couple weeks and drove home. You don't need 35s or 37s most of the time the XJ is already very capable so don't go overboard with the mods. If I needed more capability I would add selectable lockers.

Mods that help it go 70 and play in the rocks include: zj steering, RE superflex 3.5, jks disconnects, 265x75R16 trxus m/ts with gemplers ultraseal (seals holes and does a little dynamic balancing), skids over gas tank + t-case (so I don't have to lift it more).

Other toys include in-dash inverter, OBA, 2x4 rocker replacement, tailbone, dual batteries. This instead of a winch: http://www.tractel.com/us/presentation/tirfor_en.php?id_master=38 gives me 100' of pull (3000 lbs) in any direction and doesn't weigh down the front bumper or block the radiator.
http://www.tractel.com/us/presentation/tirfor_en.php?id_master=38
 
The tractel hand winch is better than nothing, but at 41lbs only weighs 23lbs less than my smittybilt xrc8 with synthetic line. With an ors bumper a winch doesn't block the radiator or take up any ground clearance. If you are seriously stuck 3000 lbs won't be enough. IMHO anyone who ever wheels alone should have a winch. Moderate lift size, proper alignment and balance, and quality shocks are the most important things in keeping a wheeler street able.
 
Here's my build. http://naxja.org/forum/showthread.php?t=1054630

Running 3" of lift and 33's. It gets wheeled around 10 times a year and is my winter DD. I built it to drive down the interstate just as well as it works on the trail. I do avoid some stuff due to clearance. I drive to Harlan, KY every year and that's around 300 miles one way. It's even been to Moab(3200 miles round trip with only a broken shock mount). XJEEPER's rig is really that clean too!





 
zachandandy said:
The tractel hand winch is better than nothing, but at 41lbs only weighs 23lbs less than my smittybilt xrc8 with synthetic line. With an ors bumper a winch doesn't block the radiator or take up any ground clearance. If you are seriously stuck 3000 lbs won't be enough. IMHO anyone who ever wheels alone should have a winch. Moderate lift size, proper alignment and balance, and quality shocks are the most important things in keeping a wheeler street able.
Click to expand...

I have a snatch-block which gets me to 6000. My hand winch (actually clydesdale not tractel, but there are no clydesdale pictures online) has a WLL of 3000 pounds, but the safety shear pin brakes at 4000. It also has the advantage of being able to attach wherever I need it (side, rear, someone else's rig). I used these winches when I used to work building hiking trails. They are slow, so if you needed to pull your jeep 100ft, that wouldn't be very fun, but I doubt I would have to do that since I stay out of the mud.

OP: Sorry, I don't have a build thread. Mostly I built this jeep in 2008 and I make smaller changes as needed.

Ben
 
Vanimal said:
i'm on 37's and 1 ton axles and i daily drive mine, 80-90mph on the highway daily. no problems. Like Cal said, as long as it's built right....
Click to expand...

Yeah but you also need a rig that will go over rocks as if you were trying to drive over them at 70mph
 
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