This idea has some back story,
Last weekend I got the chance to watch the Lake Superior Performance Rally (and great drivers like Travis Pastrana and Ken Block) and said rally also took me over some pretty nice dirt (and quit quickly I might add, there isn't much time between stages). I got to thinking...

I had originally planned on doing a SAS, but I realized how much crawling I'd be doing (ie not much) and how I'd be spending most of my time on the dirt mud and snow. So I figured I would like to build something along the lines of a pre-runner so I can still go fast, but get through what ever I encounter.

My question is, has anybody upgraded their cv joint/entire axles? I saw a 4wheel article about a tuff country lift for newer fords. They suggested going to Porsche 930 joints/axles and I noticed their pretty big in the buggy/sand-rail world. If i were to make new a-arms and beef up (or fab new ones) the shock towers could I pull off long-travel ifs? I guess I would assume I would have to ditch the t-bars, though If there was a way to keep them.

Engineering School cannot be conducive to one's wallet...

 

First off, it's an interesting idea, but lets get one thing straight... a true prerunner (as in the ones they compete with in rally racing) is a 2wd with 4x4 suspension for offroad use and better suspension travel. To make a true prerunner, you'll need to ditch the front axle and transfer case. The reason being, the prerunners are designed to run at speeds that could cause trouble in a locked 4 wheel drive mode, and since they don't use 4x4, they don't want to lug around the extra weight in competition. But, seeing as you want to run it in the mud and snow, I suppose you don't want to get rid of 4x4, so you're just going to have a prerunner style truck that is a bit more front heavy than a true prerunner.

Now that that is out of the way, the best idea for the front suspension is to make tubular A-arms and run coil overs to replace the torsion bars. The problem with that is, the coilovers would go where the cv axles are, which is another reason prerunners are 2wd. But, the problem with using torsion bars is to get the angle you'd want on the A-arms would require too high of a preload, which would give the bars a very high spring constant and would make for very harsh landings in an offroad rally race, and could potentially snap the bar if you landed hard enough that it loaded the bar beyond what it could handle (the final load is a combination of the preload and load).

As for the upgraded front axles, I don't know.

 

Yeah, I wanted to keep the 4x4, and get the suspension travel of a pre-runner whilst maintaining ifs.

I figured the t-bars wouldn't handle that type of load.

Also, after reading your 242 thread I added that to my list of wishes (along with a manual swap).

As far as the coil overs getting in the way of the shafts, If figure there's gotta be a way around that (especially if the a-arms have to be fabed).

http://www.4wheeloffroad.com/techart.../photo_13.html

That picture is what spawned my initial idea.

 

318 makes some good points. My SAS is primarily being done because of mud and snow. The stuff I get in would tear the IFS up fast. Not necessarily break it, although that is a definite posibility, but wear it out really fast. Im going to run coil springs, which would give you more flex and softer landings, but im not so sure about the sway posibilities if you come down at any sort of angle. Coils arent known for their stability at angles/speed.

And to make another prerunner point, prerunner building is not conductive to ones wallet. Price coilovers and when your wallet stops crying let me know what you think. .

How fast is fast? In 2wd with a solid front you could go pretty much as fast as you want. Youd want fullsize axles for stability and strength.

If you can fab Id like to see your end result if you go through with it. But its a TON more work than even what Im doing, and Ill tell ya first hand I kick myself in the nuts somedays for butchering the truck and volunteering myself for this project. Its coming along now and Im getting closer every day, but......... its a ton of work.

 

Read through my first post one more time, I added info about the same time you posted your reply.

That could work, but still not a true prerunner. Would be a cool build though and make for a fun toy... I wouldn't compete in any kind of rally race with something that heavy though.

But like skyshark said, look at the price of JUST the coilovers and see if the build is worth it (these are road racing coilovers, not offroad, but you should get the idea!)...

http://www.summitracing.com/search/D.../?autoview=SKU

 

A pre-runner is any vehicle used to pre-run the course, I've seen plenty 4x4 prerunners.

Someone has done a Twin I Beam suspension swap on a 1st gen for pre-runner, Twin I Beam is very simple and offers insane travel, if you want 4x4 you could do a Twin Traction Beam swap, a 4x4 version of TIB. Personally that's what I would do.

 

The definition may have changed or evolved, but the original idea of a prerunner is a 2wd set up for offroad use and rally racing.

 

not sure what happened to my post, but I revised my comparison, and likened this idea to closer to a pro 4 or pro 4x4 in one of the off-road racing series'

as far as a twin i-beam, that'd certainly be unique. I'll have to look for that build.

 

After doing some research, I figured out that for the most part I'm right about what a prerunner is/does. Hahns5.2 is right in that it is a cheaper vehicle that a big race team uses to pre-run a course before their expensive vehicles get out there and it can be 4x4 or 2wd. But, I'm right in that these vehicles are used at speeds from 50 to well over 100 mph, which is waaaaay beyond anything you'd want to use a locked 4x4 for. Think about ramping a truck in locked 4x4 and landing the front tires down first... bye bye transfer case. So, when I said they are typically 2wd, its because there is no reason for them to be 4x4 so why lug around the extra weight and have to worry about driveline angles for how far they flex. For example, to get a front axle high enough that it is out of the way of the front IFS bottoming out and not digging the axle in the ground, think about the angle that the cv shaft would have to sit at and the wear it would put on it. Then think about how much shorter that cv shaft would have to get when the suspension is bottomed out. The way prerunners are used in the race world, 4x4 just wouldn't fit in and isn't worth it.

It's definately going to be an interesting engineering project for you to make a 4x4 prerunner.

 

People commonly think of a 2wd with long travel when they hear the word pre-runner but the general idea is any vehicle used to pre-run the course.

Here's that TIB Dakota.



Here's a TTB Ranger pre-runner, of course rangers already have TTB so that simplifies things.