A few questions of longtime Chevy/GMC IFS 4wd owners.

[Buliwyf]

More good reading:
http://www.4wheeloffroad.com/project...d/viewall.html

http://www.off-roadweb.com/tech/0911...e/viewall.html

[FellowTraveler]

I fit 285/75/16 w/o lift by rolling sheet metal at the rear lower corner of wheel well then trimming the fender flare at that location. Not sure about your fender and if this would work for you.

[locrwln]

I locked mine up with a E-locker. We will see if I have any problems. I use my truck plenty offroad. Can I break it? Probably, but like most people on here, I am a finesse wheeler. I have beefed up the steering, which is the big weakness on the HD series trucks. You can look through my build thread to see what and where I have taken/used my truck and what I have done to "beef" it up.

There are plenty of trucks being used in sled-pulls, that are locked with a whole lot of power going to the ground and the front ends live.

There are plenty of trucks being used in drag-racing, that are locked and unlocked that have a whole lot of power and the front ends live. I believe the guy named Dimitri has the highest HP d-max at something over 1000hp, the front end lives and he competes in the Diesel Challenge, so a variety of tests, the front ends lives.

There are plenty of trucks that get used extensively off-road doing a lot of miles off-road in Baja as chase trucks, tow rigs, and every where else. Again the front ends live.

Do I expect to have to replace ball joints, yes, but my F350 spent almost no time offroad and the ball joints were toast at 80k miles. My chevy has 93k on it and the ball joints are still like new. I bought it at 76k, the BJ's are original.

The big thing is even though according to some, I should have bought a car to do my off-road work vs. using an IFS chevy, is yeah the IFS is sooo much nicer to drive both on and off road over my F350. My ford beat the crap out of you on anything other than smooth gravel. The chevy handles it much better and I still have the crappy stock shocks for now.

Jack

[redthies]

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I will admit I am a GM fan. I might be a little bit biased, but I do not love the IFS, And I do not love the lowrider stance the way they come from the factory.
However I have seen the new dodge IFS trucks that sit practically on the ground, same goes for the new fords.
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SO dont single out GM they are not the only ones.

I am not brand loyal like a lot of people. I believe each manufacturer brings somthing good to certain segments of the market. You just have to choose the appropriate vehicle for the job.

That said, I quoted you because the discussion is about Heavy Duty trucks. We all agree (or most of us at least), that IFS is OK in 1/2 tons. It's not great, but for the intended use of a 1/2 ton, it works. Neither Ford or Dodge use IFS in any of their HD 4x4 trucks.

If I were in the market for a new HD 4x4, I would have to buy a Dodge for three reasons: Cummins, manual trans, and solid axles. Power Wagons are also a good reason!

[Buliwyf]

I don't want to single out GM, Ford, Toy, Dodge IFS is no better. But all of my IFS trucks at work are GM's. Everything else is solid axle or one wheel drive vans.

I don't think it's fair to use drag racing and tractor pulling as proof of anything. No turns, no rocks, no flex during any of that. Going up a slippery hill with the steering cranked and the chassis flexed is the death of IFS. IFS is fine in a straight line.

I don't have to look far to see evidence of blown up IFS, it happens. Aftermarket CV axles are unfortunately very expensive. It's ironicly, sometimes, cheaper to SAS.

[motrhed]

Well, looks like I will be a ginny pig here. I have had numerous trucks, wheelers, etc for the past 40 years of driving from custom axles to HD tow rigs with beam axles. My JK is set up pretty decent as a do it all kinda truck- tote kids, wheel most anything, or DD. However, I just sold my '11 F250 diesel- awesome rig, but found an '00 2500 4x4 Suburban w/ 35k miles and barn doors. Plan is to add a 2" front lift via torsion key replacement, fit some 285/75-17 A/Ts on H2 wheels, use as a DD, and tow rig for the JJ, M101, and a single car trailer. Also explore the simple gravel forest roads, etc. May add a Detroit rear, ARB front bumper, and a winch. Also considering an Aluminess with rope in lieu of cable to keep front weight down. I have read as much as possible, and think/hope the comfort will improve and the minor build will aide in keeping it all together and reliable. Time will tell... But my logic is the 'burb for the mundane and JKU for the fun, and not build any more trucks.
Any thoughts, input, advice appreciated, and I promise to report back here on a regular basis. First point being a 500 mile ride home without issue, 16.7 mpg and a sweet ride!!

I would not recommend a torsion key lift if you want good ride quality or to preserve front end part life. The torsion key lifts create a rough ride and are hard on ball joints, tie rod ends, C/V's, etc. Look for a true mild lift that doesn't cause the A-arms to sit at a more severe angle. There are many different products to choose from, some good, some crap, some cheap, some overpriced - do your homework and find the one right for you.
On my '07 Chev 2500HD Dmax, I had a key lift and changed it out for a 4" Rancho set at a 3" ride height with 305/75R16's and RS9000's to restore the ride quality and longevity of parts. It seems to be working well other than the loss of ground clearance as compared to the key lift (not a huge issue for me as I don't drive this truck in knarly off-road conditions... that's what the toys are for!). If you plan on keeping your Burb, a proper lift will pay off in the long run in both comfort and maintenance.

[Larry]

I would not recommend a torsion key lift if you want good ride quality or to preserve front end part life. The torsion key lifts create a rough ride and are hard on ball joints, tie rod ends, C/V's, etc.

Contrary to popular belief, adding torsion bar keys or adjusting (cranking) the torsion bars DOES NOT affect ride quality. Torsion bars have a fixed spring rate built into them, cranking them does not change that by adjusting them up a bit. What affects ride quality is the fact once the torsion bars are adjusted for higher ride height the suspension bump stops are driven into the upper control arms and the shocks get overextended and run out of travel. That is where the bad ride comes from.

All that really needs to be done is trim the bump stops or remove them all together and add longer shocks or shock spacers. My white Silverado above had torsion bar keys and torsion bars adjusted to gain as much height as possible without putting an excessive working angle in the balljoints or CV shafts. With the bump stops removed there was no change in ride quality from stock even with around .75 to 1” of lift gained through the combination of tbar keys and cranking the tbars. In fact, I think it even road smoother with the bump stops totally pruned off with the bars cranked up a bit over how it road stock. Of course, GM HD truck IFS does not ride near as well as GM claims it does over a Dodge or Ford coil sprung SFA. About the only thing IFS on an HD trucks is good for is predictable steering at higher speeds. Coil boinger SFA axles tend to have more noticeable bump steer while GM IFS has noticeable toe rod and idler arm carnage.

I’ll take a Dodge SFA over a GM IFS any day and I am supposed to be a GM lover kind of guy. Old Chrysler cars had tbars many moons ago. GM medium duty trucks also had tbars back in the 60's which GM finally figured out IFS did not work well on a medium duty trucks and returned to I-beam axles. Not sure why they thought tbar IFS was a good idea on 8,600+ lb trucks again in the late 80's through today.

These guys do a pretty good job of defending the torsion bar adjustment vs. ride quality if you read their info. Same thing the old bigbody rear wheel drive 60’s and 70’s Chrysler hot rodders have been saying for years.

[Rovertrader]

Does anyone have first hand experience with the Cognito kits?

[Balzer]

I am not brand loyal like a lot of people. I believe each manufacturer brings somthing good to certain segments of the market. You just have to choose the appropriate vehicle for the job.

That said, I quoted you because the discussion is about Heavy Duty trucks. We all agree (or most of us at least), that IFS is OK in 1/2 tons. It's not great, but for the intended use of a 1/2 ton, it works. Neither Ford or Dodge use IFS in any of their HD 4x4 trucks.

If I were in the market for a new HD 4x4, I would have to buy a Dodge for three reasons: Cummins, manual trans, and solid axles. Power Wagons are also a good reason!

I understand the discussion is about the HD trucks. However I thought there might be some value knowing the half tons (consitered too weak for a locker) dont blow appart like some rumors might lead a person to think. I have abused the hell out of several and while other parts break the center diff holds strong.
I see a lot of people jumping to "Petersens off road" red sled project as proof, but has anyone seen how rough they really are on vehicles? Its not a matter of if they break something its a matter of when will they break something. They dont need their trucks to get them to work the next day, they dont have to pay for all their parts, they consiter a budget build to be under $20k. Dont get me wrong I like the mag. but they are not an accurate real world example.
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I really dont want to sound like some sort of GM IFS advocate, Like I mentioned before I dont love it, But if you listen to everything people say then a GM truck is weaker than a roll of wet toilet paper, jeep axles will break if you look at them wrong, range rovers will leave you stranded every time, and so on and so on.
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What I really like to see is when a you get on a forum such as this and many others and see someone ranting about how weak something is, just to find out its some 14 year old kid who has never owed drove or worked on whatever he is talking about. Its not the kids fault, he gets his info from the introweb, he sees countless people saying "dont buy this, I farted and broke the axles and blew the transmission out all at the same time, and this was the first time off road"

[Larry]

Does anyone have first hand experience with the Cognito kits?

I had a set of their tbar keys but that is it. I had grandiose plans to add their upper control arms and tie rods to my ’05 HD but decided to sell the truck before I bought that stuff. I’ve read a lot of good reports about them on various websites though.