Independent Rear Suspension

I was wondering if anyone has attempted to swap an IRS from something like a C5 corvette or Jag into an XJ. I know that these rear ends are strong enough to handle the power. Does anyone have any ideas as to why or why not this would be a good idea?

Two reasons off the top of my head.

1. Very little travel without extreme modifaction. Search for Walker Evens Rig on POR

2. $$$$$

You want a solid rear axle for a off road vehicle (in general).

If you are trying to build a sports car out of a xj then I guess you could consider it, but think of all that work!!!. And I am not sure (off the top of my head) how you are going to make it perform without a solid frame to distribut the stress, loads and forces?

Michael

Lets not get too hasty with the solid rear axel for off-roading. All of my buggies are independant rear axels. If you want to go fast...go IRS. If you want to wheel.....(at least until someone developes a better system then what is available now)...stick with the solid axel.....
I am looking forward to a quality....simple.....effiecient....reliable...servicable....IRS for my Jeep.....
still waiting.....

Thanks guys. My reasoning behind this idea was to allow for multidirectional flex. I was still wanting to set it up like a solid axle, but have the added advantage of keeping all the tread flat at each corner. Think it can be done?

Seriously Walker Evans runs exactly what your talking about. And Its sick. But then again. Your gonna need about 20,000k to really make it happen front and rear.

So is the $$$$$$ the reason no one really attempts to do this swap, or is it that they are just too unreliable? I guess My question is this setup reliable enough to offroad?

csudman said:

Seriously Walker Evans runs exactly what your talking about. And Its sick. But then again. Your gonna need about 20,000k to really make it happen front and rear.

Click to expand...

Ran,

He's back to solid axles

mark

Having the tire flat isn't always desirable - often you want the tire to be angled.

Independant suspensions have a major advantage at speed - so if you are building a jeep speed truck - then it would be beneficial (if you could give it enough travel). But at speeds where forward traction is the key - solid axles are far better. This is the reason that Hummvees are designed with IFS/IRS and why they are completely out-classed in rock-crawling. They were never intended to be rock-crawlers - the name it self comes from HMMWV: High Mobility Multi-Wheeled Vehicle. The High Mobility part is key. Anyway - ditto what everyone else said... it's possible - but would cost a fortune. If you want street-speed: buy a sports car, it's cheaper and faster than making an XJ one. If you want slow-speed off-road, stick with the classic solid axle setup. If you want off-road speed, buy yourself a used hummer - it will probably be cheaper than try to set-up a well-working IRS on an XJ.

But to answer your last question (reliability): It all depends on how you build it. If you took the suspension from a C5 and dropped it under an XJ - you'd be in serious trouble, I think. That suspension is not designed for large tires, large travel, or getting hit by ANYTHING much less big rocks. For that matter, it's probably not even tough enough to survive the 4.0 in low-range. That's nearly twice the torque of the vette! not to mention the effect larger tires would have on it. I don't think it's worth it..... but good luck in any case!

EDIT: Kudos for thinking "outside the box" - never be satisfied with the status quo just because it is that.... always seek out the REASONS behind things to determine whether balking it is a good idea. (it seems like that's exactly what you did here... good for you!)

Just 4 link the rear like Curt LeDuc http://www.truckworld.com/Racing/Off-Road/2000-baja/Baja-2000.html

30 inches of travel should be sufficient

An IRS can be made to be reliable, IRS off-road race buggies and Truggy's are reliable, although getting it to work well rockcrawling is not that easy. A good linkage system with solid axles can stick the tires into the rocks, in a more reliable pattern, than the IFS/IRS systems built to date (including Walkers experiment). An IFS/IRS system can be made to do the same (rake the front roll axis and almost level the rear roll axis to keep the tire contact pressure from unloading in a climb over the rocks) but the cost, space constraints, and attention to detail is overkill for most people.

The cubic cost is a major factor, for everyone except for sponsors like Toyota or GM. Ivan Stewart's PPC trophy truck is essentially a very trick IFS/IRS Class 1 buggy with truck like body panels. It is lighter than most of the other TT competition running straight axles, but not any faster (it is lighter, running less HP). GM also loosely sponsored a mid-engine IFS/IRS Blazer in the early 90's with less productive results (although it did look cool with SLA A-arms at each corner). These vehicles look great WFO in the desert, as do solid axle trucks with 26+ inches of wheel travel at each corner.

C2-C5 and Jag IRS parts are not that beefy. The C4/C5 aluminum pumpkin guts are D44 (I have one if anyone needs it). The C2/C3 pumpkins are heavier duty, a version of a GM 10-bolt, but no lockers are available (I have a spare of these as well, but I am keeping it). The Vette racers have Currie or Tom's build 9-inch or D60 pumpkins to handle the HP.

Eventually someone with $$$$$$ will build an IFS/IRS rockbuggy with 9-inch center sections and halfshafts driving portal boxes at the wheels, and make it work (although I imagine the low buck leaf spring straight axle guys will be just as competitive, until the IFS/IRS add active suspension and traction control aids). What is likely to occur is that one of the ATV manufacturers will probably build a small scale version of what works for rockcrawling (with active suspension and traction control) and someone will copy it full size.