IFS vs Straight Axle

I was watching the first episode of Dark Winds on Netflix and saw this axle on a truck and thought it was unusually high and skinny.

I know my 3rd gen has IFS that seems way beefier. Why does this truck seem so fragile?

 

IFS=more comfortable ride. SA=more articulation. The badass Suburban happens to have a higher center of gravity which shows the body roll... and it's a tv prop. The Suburban would probably look less fragile with bigger tires to fill up the wheel wells. Apples to oranges. They both are rad.

 

Solid axles can be made much stronger than IFS, much more inexpensively. There's fewer joints, basically.

You can buy a stronger axle to replace one, or modify am existing axle by bracing and plating the housing, buying a higher strength ring and pinion, stronger axle shafts, stronger u-joints for a steer axle etc.

With IFS there's a lot more joints, and both ends of the axle shaft have to articulate. Now load them up and add shock loading (like a wheel spinning in air, them the truck moves and it lands while spinning) and they're fundamentally weaker.

That old suburban has quite a bit of lift, which makes it appear smaller, but that might be a 1/2 ton truck axle. Plenty strong for the engine/trans/tire combo

 

Early IFS systems (up to maybe the mid-late 2000s or so) were definitely weak. Small CV joints that broke often, flimsy steering linkages (often consisting of thin tie rods and a centerlink on weak idler arms), weak knuckles & A-arms, and their mounting points on the frame. Small differentials often had poorly-reinforced aluminum housings that burst if used hard. Travel/articulation maxed out at about 6-7" or so (Ford's TTB IFS was an exception). During this time period, it was very common to swap out IFSs from all makes for solid axles.

Modern day IFS on the other hand (at least ones such as under our 2nd, 3rd, and (I assume) 4th-gen trucks) have improved considerably, at least in terms of torque (big-tire) handling ability. The CV joints & differential gears are closer to par, strengthwise, with that of solid axles on similarly-sized vehicles from the last couple decades. Steering knuckles and control arm mounts continue to be weak spots, but without all the rest of the weaknesses, it becomes easier to address the ones that do remain. Travel numbers in the range of 8-9" are easier to obtain as well (more so with long-travel setups).

Regardless of it's strength, like was said above, it will always be easier and cheaper to lift & build solid axle suspensions for offroad use (which I think is a big reason why the FJ Cruiser couldn't hold its own in sales next to the Jeep Wrangler. I suspect Ford's new Bronco will eventually meet the same fate).
IFS needs lots of things like drop brackets and various reinforcements (A-arm tabs, skids, reinforced/beefier knuckles, etc.) to be similarly-capable & durable, which of course this drives up costs and complexity. And even after all that, IFS will rarely have the same amount of articulation that a solid axle is capable of, even with long-travel (this matters a lot if you're rock crawling, but usually less so elsewhere).

 

I had a 84 Toyota with a solid front axle, she had leaf springs front and back and she rode like a lumber wagon. Tough as nails and you could put her in 4 low and get out and walk beside her if you wanted to. My 17 has IFS and rides like a marshmallow floating on a cloud compared to the 84. In extreme off road conditions I’d go with the 84 over the 17 but I don’t do extreme off roading anymore so my old bones really enjoy the marshmallow.

 

My dad had a Suburban like that when I was a kid (although not lifted). It was awesome, and had a lot of room inside.

Anyway, I've got a Jeep TJ with solid axles. It excels at slow speed with all kinds of flex, and I'll take it places I wouldn't take my Tacoma. But my Tacoma has a softer ride, and I can drive it faster on dirt roads.

 

fragile ? not hardly . those were those were napco conversions done originally only for military and gov vehichles .