I'm a newbie with a question for those more knowledgeable. Is a live axle always better that IFS. If so why? Wouldn't IFS give you more ground clearance if you lift the truck, at least for the front end. If live axles are so great, why does the original Hummer (the ultimate off roader?) have IFS?

The H1 is designed to travel a variety of vast terrain and do it at speed. IFS is MOST instances is a better option for speed and controll. The H1 is equipped with locking differentials, great approach and departure angles and 37" (I believe could be 35" but I'm pretty sure they are 37") tires to further aid in ground clearance.

IFS generally has more controll due to the fact that each tire acts independantly as opposed to a straight axle in which one wheel will act and react to what the other wheel is doing.

The advantages of the axle are strength at extreme angles of articualtion and fewer small breakable parts. With the simplicity of the design you can safely get more ride height and tire clearance from a SA without the use of drop down brackets and with it larger tires and more articulation without sacraficing strength and reliability. That's why you will see more dedicated rock crawling and mud bogging vehicles with a SA.

But with that height and tire size you lose handling and cornering stability. A desert truck at the other extreme, gets their articulation (or travel) from increasing track witdh by using longer controll arms and longer rear axles (longer wheelbase as well) thus keeping the ride height to a minimum and retaining high speed stability and cornering ability.

(Good reply)

I'd throw in agreement with the IFS being better for high speed work, and the live axles being better for rock crawling...a live axle can articulate in ways that an IFS rig can only dream of...the money it takes to get a IFS to get the same potential wheel travel is insane, and, after al that, it STILL can't outperform a live axle.

You reverse all of the above advantages/disadvantages on a high speed run across Baja, etc...where the IFS follows the terrain better as the one tire's path is not interferring with the other tire's path (Independent suspension)...and the live axle would be juddering all over the place, etc.

A Hummer is not the ultimate off roader..its almost useless on most trails actually due to its bulk...it is well suited for dashing across dunes or similar terrain, and crossing open country, fording, etc...and, if the trail is wide enough, it's twin lockers can get it through some pretty tough obstacles (A front locker helps an IFS rig even ore than it helps a Live axle rig...one tire ends up airborne more often on the IFS...)...

So, an H1 is pretty damn capable, but it is not the ultimate off roader, and the H2 is a somewhat more capable Suburban, etc...

Never saw an H3 in action...at least it looks like it might at least be able to FIT on a trail.

Don't forget the H1 has portaled hubs (for that extra bit of clerance) and yet still relies quite heavily on it's lockers for traction.

The ultimate IFS:

Massive travel. 25+ inches
Strength and stability at speed.
Max speed 130-140 and 750+HP

Without lockers, the H1 would be screwed...they always have tires in the air unless the terrain is flat.

And for a counter photo, here is my friend's slightly modified XJ:

FYI, not everyone knows that there is a long arm IFS kit for Xterra HERE

It was touched on, but the solid axle increases the traction in an off road setting because when one tire is up on an obstacle, the other tire is forced into the ground providing more traction. Conversely, when an IFS tire is up on an obstacle, the other tire is not being force onto the ground, it will just go to its limit in down travel. This is well illustrated with the two pics above. The H1s front right tire is just hanging there providing no additional traction. The jeep under that shows that the downforce from the tire up on the obstacle is what's driving the tire into the groung for added traction.

I've seen H1s take bypasses around fairly technical trails that lightly modified, thinner, shorter wheelbased vehicles could overcome.

Now that's what I'm talking about.

To address the above opinion that a M998 HMMWV is practically useless without lockers, keep in mind that military versions do not have lockers and use a torque biasing differential instead of lockers. Our trucks are amazing in their capabilities and always deliver. That might be based on the fact that they arent yours and if you break it you might not have to buy it. Oh well just my opinions.

Tim

I'll second what's been said here, and add that the H1 is the jack-of-all-trades off-road vehicle. It's a tow vehicle capable of pulling a howitzer up a dune, it's a desert racer, and it's a rock crawler. It doesn't tow as well as some other vehicles, it doesn't go as fast as a trophy truck, and it doesn't crawl like a built-out Samurai, but there's no other vehicle that does all those things combined like the H1.

Except the Toyota FZJ80.

Just kidding.

As a guy who went from IFS to solid axle, I can verify that the on-road handling of the SFA is comparable to the IFS. I still like the IFS for its comfort, and I could go faster on a bumpy trail in my Xterra than I can in my FZJ80, which, at speed, is all over the place. I've been up to Calmini and seen the SAS kits that they have, and have heard the reviews on their performance, and if I still had my Xterra, I'd go for it. The Xterra with SFA is a bad mofo.

The Military Torsen units are actually a step up from lockers in traction off road, as they actually proportion the traction to the tire with the most grip, rather than the fastest spinning tire, or just making them turn at the same speed...as an open diff or a locker do.