What are the Real IFS Worries? - also...IRS Swap Anyone??

Smith

New member
Recently joined the forum and have learned a wealth of info. - thanks for everything. :coffee: I'll post a build thread here pending how this turns out:


I repeatedly read that people here are 'worried' about using GM's IFS or any IFS for that matter and advocate the SAS...why?

The H1 is reportedly one of the best off road vehicles designed...it ONLY uses Independent Suspension at all 4 corners. I think it's a brilliant idea to not have any axles to get in the way of hitting protruding rocks, stumps, and such.

So, after reading all that I can...
- Is it the torsion bar flex?
- Angles that carry the A-frames?
- Size of the A-Frames?
- Grade/Amount of steel used in production?
- Weight distribution?
- Half Axle quality?
- MPG?
- Max Hwy Spd?

Has any ever done the reverse - IRS swap the rear axle to eliminate the transfer case & axle?
 

haven

Expedition Leader
The solid front axle suspension has been with us since the Conestoga wagon. It's proven to be a durable and inexpensive solution to suspending the vehicle. It's easier and cheaper to modify a solid front axle for extra wheel travel and for extreme articulation angles than it is to modify an IFS. And since heavy trucks use solid axles, there's a macho belief that "real trucks" only use solid axles.

However, the times are changing. If you look at the designs the military is reviewing to replace the Humvee, they're all IFS. Here's an example from International:

640px-International_FTTS.jpg


And the designs for the second generation of MRAP vehicles include some IFS models. Here's one from Oshkosh

oshkoshmrap.jpg


Compared to solid axles, IFS has greater high speed stability. That's why vehicles like Trophy desert race trucks and the Ford Raptor use IFS.

The most common way people improve their vehicles for off-road rockhopping is to lift the suspension so they can have long wheel travel, and to fit larger tires. Aftermarket kits for solid front axle vehicles are plentiful. IFS kits are more complicated, harder to install and more expensive. But there are a few available.
 

Rot Box

Explorer
Welcome to the forum :)

For me IFS isn't the problem--its what some manufactures used to make it work that I really dislike. I personally hate torsion bars and idler/pitman arms no matter what vehicle they came on. That said I really like the rack/pinion and coil over struts on my 4runner and wouldn't dream of swapping it out.

Theres a guy that put IRS on a new Tundra in the Toyota section thats worth checking out....
 

Schattenjager

Expedition Leader
You are going to get some interesting responses, I bet.

In the most general of terms, IFS can not articulate as well as a solid axle setup. I have had and modified both. The IFS devotees will cry foul, but without a solid axle out front, they really don't count and should keep their bleating to them selves. :)

Once again, it is pesky physics that ruins the day for the IFS crowd - looking at the small arc of travel the IFS suffers being hinged on the OUTSIDE of the third member, articulation will suffer. The hummer is a portal setup with LONG arms centrally hinged and that allows for more articulation than my tricked out IFS 05 Tacoma could ever hope to have had. But those same elements make IFS much nicer to ride around in on the day to day (99%) driving we do. The smaller components represent slightly less mass for the drivetrain to deal with and are, ultimately, less expensive to manufacture and service. That is why most rigs have gone to IFS - build costs and road comfort.

Solid Axle rigs drive like trucks and will, due to the heavier duty guts, be less efficient. The super long travel comes from the fact that one wheel is the hinge for the other, so flex is easy to come by, relatively. The housing is robust, typically, and so are the guts. Typically.

Will an IFS rig go the same places off road as solid axle will? Very Likely. I was a Rover guy for many years (solid axles) and made the enlightened jump to Toyota and a new Tacoma. Did all the stuff (there are truly many options, but all are just variations on a theme) and explored a lot of Alaska (there for 5 years) and Colorado. Went everywhere I wanted, but what I did notice was the lack of suspension compliance. Again, the limited travel and arc of the suspension had my truck bobbing around like a cork in a troubled sea. I got where I wanted to go, but was worn out and hoping all the gear was intact when I arrived. Now having gone back to a solid axle (FZJ80 Cruiser) I can retrace my paths in much more comfort (and safety, really) due to the compliance of the solid axle. Night and day really.

I will look forward to following this thread as I'm sure there are plenty here who can bring a lot of info to this discussion.
 

Buliwyf

Viking with a Hammer
The tie rods are often slightly different in length or angled differently. The incorrect geometry causes the suspension to tug on the tires/tierods every time it moves. And it moves superfast when you ********** a pothole. That tugging can seriously weaken the tie rods. Haveing the IFS tug away with your steering cranked and on the throttle is a KABOOM waiting to happen.

A properly done rack and pinion steering is the best solution. If you can size and place the rack in just the right spot, you can minimize the above problems. Goofy steering boxes and pitman arms left over from solid axles don't seem to make any sense at all when used with IFS.

Also the ground clearance under IFS is variable. When you apply the brakes the truck noses down and ground clearance is reduced. IFS bottoms more coming down obstacles. A solid axle's diff has the same clearance from the ground, even when the truck noses down under braking.

The HUMVEE's are built extremely tough and expensively. They spent the time to work out the IFS bugs. But bigger and heavier military trucks still use solid axles. Trying to package hardcore IFS in a regular truck is very hard to do. Look at the guys squeezing custom fabbed offroad arms on the front of the Raptors, deosn't look cheap at all.

Solid axles are just plain tough and simple. Making an IFS that can match that is $$$$$$$$$$$$$$$$$$$$$$.

Rockcrawlers still prefer solid axles, as do: Semi's, cranes, dumptrucks, etc. etc.
 
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warrpath4x4

Adventurer
where do i start lol

The IFS on hummers is not what makes them strong or really any stronger than a one ton pickup, i used to be a mechanic for the army and worked on hummers ALOT even though i was a tank mechanic. We changed out CV axles just as much as any chevy pickup that gets abused as hard, the strong point on a hummer is the portal boxes (which helped with CV angle).

I dont think as much on an expedition forum but on other off-road forums where guys are putting 38 and 44" tires on their rigs with IFS is where you end up breaking everytime out. I know a guy with a dodge 318 engine with duece axles and he breaks a shaft almost everytime out, alot of it has to do with your driving skills.

oh and i cant tell you how many times we got stuck in those damn things either
 

TheGuyJones

Observer
There was an issue of Fourwheeler magazine in which someone had a 2005 F-150 rearend swapped out with the IRS from an Expedition. They ended up modifying an F-150 lift kit in the front to 4" and then a custom setup in the rear. I wish the company he had do it would turn that into a kit so that Expeditions wouldn't be limited to only spacer lifts in the rear. Wishful thinking. The truck was used as a chase truck I believe for Baja races.
 

Ponyracer

Adventurer
- Is it the torsion bar flex? Not really an issue
- Angles that carry the A-frames? Prob is, like mentioned above they just can't travel in enough arc for usuable wheel travel unless you go to stupid expensive longarms, ie, trophy trucks.
- Size of the A-Frames?See above
- Grade/Amount of steel used in production?They are designed for on road comfort, not load carrying
- Weight distribution?Not really an issue
- Half Axle quality?See above about on road comfort. The chevy IFS trucks were NEVER designed to be abused offroad. The only rig that I can see that was designed for max travel and offroad use from the factory is the Raptor.
- MPG?I don't see this being a big difference, the weight is still there in the IFS components so the diff over a solid axle truck would be negligible
- Max Hwy Spd?No difference

Has any ever done the reverse - IRS swap the rear axle to eliminate the transfer case & axle?Transfer case will be there wether its a solid axle or an IRS. It splits the torque to the front wheels so unless your bldg a 2wd IRS truck then u will have one

It all comes down to design, PERIOD.

IF dodge and ford wanted to design a newer ultra HD IFS and IRS for that matter they could, (see the HD military trucks posted above), but why? Tooling, added r&d, etc. The solid axle has worked perfectly since the first haycart was built by a cave man. If it aint broke, DONT FIX IT. In my opinion trucks that are 4 wheel drive should not have IFS period. Unless it is a truck designed for offroad racing, ie, Raptor. Trucks are meant to haul stuff, heavy stuff, leave the IFS/IRS on the cars where it belongs...


Threads like this always remind me of a buddy I was stationed with in the UK. He bought a sweet little xtra cab tacoma, about a 2005 with the locker in the rear, skid plates, etc. He was very proud, rightly so, it was a very smooth riding truck on the street. We went to an offroad playday, they had an articulation ramp so after he talked up his ifs wonder he proceeded to drive up it. Actually he drove about a foot and a half up it and it lifted the rear wheel. Once we composed ourselves after our fit of laughter we proceeded to take our jeeps and max the ramp, one guy even drove off the end iirc. I believe I got 39" of vertical travel before I lifted a tire.

Was that yota a joke offroad? YUP, did he have the best riding truck on the street? YUP. It's all about design, use the IRS where it's designed for, on the pavement.
 
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Smith

New member
Thanks for all the responses. This is mostly what I expected. There are no real world problems with Independent Suspension outside of how it is currently mass-delivered to the public...whatever the reasons may be. (Shareholder Value!! haha)

I tried messing with some designs on how to create better articulation on my GM last night, and I might as well build a new truck from scratch. There just isn't any great way to increase the arc of travel (as stated) without essentially building a whole new suspension under the current; making the truck 8' in the air.

After all that was done, I thought...hmmm...even if I design the smoothest running IFS/IRS truck this side of the river, what happens when it does break? (All things break). As for Overlanding, I guess it's best to take a vehicle that can be repaired everywhere instead of just a fabricator's garage. I'll save my money for food & fuel. :beer:
 

4x4junkie

Explorer
Yeah you pretty much got it. Getting better flex and better reliability (strength) without a bunch of full-custom parts and blowing out your bank account pretty much leaves the SAS as your only practical option. Plus the fact many gear & locker manufacturers are afraid to touch a lot of IFS diffs because of weak OEM housings, CV shafts and other parts.

Ford's TTB IFS is a notable exception to the above, however it too isn't without a few quirks that if you don't know how to deal with them, can end up nickeling & dimeing you as well (they are very sensitive about steering geometry for example, which the lift industry did absolutely no favors at all for them).
 

FellowTraveler

Explorer
Yeah you pretty much got it. Getting better flex and better reliability (strength) without a bunch of full-custom parts and blowing out your bank account pretty much leaves the SAS as your only practical option. Plus the fact many gear & locker manufacturers are afraid to touch a lot of IFS diffs because of weak OEM housings, CV shafts and other parts.

Ford's TTB IFS is a notable exception to the above, however it too isn't without a few quirks that if you don't know how to deal with them, can end up nickeling & dimeing you as well (they are very sensitive about steering geometry for example, which the lift industry did absolutely no favors at all for them).

Chevy/GMC 3/4 & 1 ton + IFS differential housings are very strong and aftermarket does indeed provide locker carriers, gear sets etc for em, the axles & CV joints are strong too. All thing being equal or not if one beats the snot out of any drive-train it will break eventually.
 

Ponyracer

Adventurer
the axles & CV joints are strong too.

HAHAHA He said Chevy IFS, CV, Axle, and strong in the same sentence.

Strong in relation to what? A 1992 nissan sentra cv and axle? Yup your prob right.

May I remind you of the "project red sled" built by Petersons 4 wheel and offroad a few years back? I was a fan of IFS since I came over from playing in the sand until I saw the trouble they had with that truck.


We should have known better, but we thought we would try the elusive front dig. All was going great as the big behemoth was crawling around and we felt the IFS might actually live, so we headed for some rocks. Now remember that this was with the front diff unlocked, and after the front-dig maneuver, which worked but made some bad noises, we shifted back into four-wheel drive. We crawled into the rocks, which were more basketball-size than Yugo-size, and heard some silly poppin' and banging up front. We crawled out to check it out, and both halfshafts looked fine, both the high-dollar RCV passenger-side and the original driver-side stock version. But then we noticed the front aluminum housing was blown in two and dribbling gear lube, and the time on our watch was just five minutes since low range was engaged.



Read more: http://www.4wheeloffroad.com/projec...4x4_truck_red_sled/viewall.html#ixzz1tErjrhhC

Bottom line, IFS/IRS has it's place, but it will NEVER be superior or even equal to a solid axle in a factory built setup when used off the pavement.
 

FellowTraveler

Explorer
HAHAHA He said Chevy IFS, CV, Axle, and strong in the same sentence.

Strong in relation to what? A 1992 nissan sentra cv and axle? Yup your prob right.

May I remind you of the "project red sled" built by Petersons 4 wheel and offroad a few years back? I was a fan of IFS since I came over from playing in the sand until I saw the trouble they had with that truck.


We should have known better, but we thought we would try the elusive front dig. All was going great as the big behemoth was crawling around and we felt the IFS might actually live, so we headed for some rocks. Now remember that this was with the front diff unlocked, and after the front-dig maneuver, which worked but made some bad noises, we shifted back into four-wheel drive. We crawled into the rocks, which were more basketball-size than Yugo-size, and heard some silly poppin' and banging up front. We crawled out to check it out, and both halfshafts looked fine, both the high-dollar RCV passenger-side and the original driver-side stock version. But then we noticed the front aluminum housing was blown in two and dribbling gear lube, and the time on our watch was just five minutes since low range was engaged.



Read more: http://www.4wheeloffroad.com/projec...4x4_truck_red_sled/viewall.html#ixzz1tErjrhhC

Bottom line, IFS/IRS has it's place, but it will NEVER be superior or even equal to a solid axle in a factory built setup when used off the pavement.

I remember this "so-called test" using the doctrine of if we beat it hard enough it will break. The photos in that article show a 1991? truck with sheet-metal lower control arms not forged so it begs the question what else was light duty?

Perhaps, you forget this is not a beat the crap out of it or rock crawler forum.

Now, how many individuals with expedition builds would be so foolish as to beat their trucks until they break? I think you can't find any here!
 

Ponyracer

Adventurer
That is true, I'm sure they did abuse the truck more than the average Joe would. However, Why build a rig with a known weak link? Wether you want to or not, occasionally even the most careful wheeler/adventurer/whatever "beats" on there vehicle by say accidently sliding off the trail or dropping over an unseen ledge etc.
 

Buliwyf

Viking with a Hammer
Perhaps, you forget this is not a beat the crap out of it or rock crawler forum.

QUOTE]

Maybe, but I want to know I can run a locker in the front and still be able to get home at the end of a nice weekend. I wouldn't put a Detroit locker in the front of GM IFS, or any 1/2ton or less IFS. But I've got no such worries about a solid Dana 60.

It's ok to call GM IFS "not broken", but I would never call it "strong". Strong isn't IFS. Maybe it's fair to call it "ok for street use" or "small farmers seem to do ok with it" or "works fine for 2-3 hunting trips every year". But "strong"?......nope, no way.

I'll keep an eye on the scrap metal bin at work. Pretty sure I'll find IFS shrapnel in there long before any Dana chunks.
 
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