IFS Lift Keys

[special-K]

I got a '95 K2500 Suburban is December. My intentions are to buy the lift keys and longer shocks but in the meantime I just cranked the torsion bars. I did this on my '92 K3500 I owned since new and put 335k on it with no front end issues. I understand the benefit of the keys is they put it up like cranking does while not affecting the ride. I also understand the a-arms limit lifting either way you go. Talking to a guy yesterday, he says the local 4wd shop told him the keys are bad news, that you will eat up axle boots and ball joints. Sounds like hot air to me. I've had no issues with cranking the bars up so how would using keys change anything, except allowing a tad more travel (down)? Down is good. It's up (droop) that is the issue when lifting. Down puts it closer to stock position. My '92 was ready for it's first ball joint replacement when I stopped using it. I think it was just one upper I found lose. I was planning on new loaded a-arms to replace the aged bushings. The ball joints lasted as well as the bushings. Can't ask for better than that. Just wondering what others say about the keys. I think it's hogwash.

[Mike C]

All the keys do is re-index the torsion bar. They do the same thing as cranking the load bolt, they usually just allow more movement than cranking the bolt.

The IFS is designed to operate in a relatively narrow range, and moving things out of that can accelerate wear on ball joints, CV joints, and bushings. But no guarantee. GM used something like 3 or 4 different keys depending on the truck and its options.

So depending on what keys came in the truck and how high the bolt is cranked you can get out of the range of acceptable for all the front end parts. Obviously 4" is out of the range since those lift kits come with front diff lowering brackets and all sorts of other crazy things.

Cranking the torsion bar doesn't change the rate, just the angle at which the key is indexed. This is the same thing the new key does with the load bolt not screwed in all the way. The weight of the vehicle dictates how much the torsion bar twists so when you move the bolt up it causes the vehicle to rise since the same twist is on the bar.

[b454rat]

Keys are just a way of cranking it up more. Glorified crank is all they are....

[special-K]

I know what happens with both methods. I just don't see how this "expert" can say these things will happen with keys and not cranking. The keys can't crank it any higher than cranking on the bolts. The a-arms are the limitation. I've had a '92 and a '95 K3500 with cranked up torsion bars and never had front end issues. I knew better than get all I can out of it. I never felt it hit the limit on droop either. I don't think the pre-99s had the keys, yet. I thought that came along in later trucks. I'm planning on staying with what I have. No need to spend money for nothing. I run 285/75s and 255/85s on these trucks and a couple inches is all it needs

[Mike C]

Actually, the keys can crank it a LOT higher than just the bolts. Because they re-index the torsion bar relative to the frame. The idea is that it lifts the truck while keeping the load bolt in the lower part of it's travel so you can use it to level rather than having it cranked all the way in. So if you crank the bolt up and you have the lift keys, you can get all of the front end parts out of the sweet spot where they work without excessive wear and binding.

If you work the truck hard (pulling, mudding, bouncing, etc.) you can cause the half shafts to overextend as well if it's cranked too much. Once again why 4" lifts and more lower the differential and the torsion bar mounts.

One of the reasons some people have problems and others don't is it depends on which key was in the truck originally. Cranking the bolt all the way up on some raises it more than others.

[dieseldawg142]

i have been running forged 1.5-2" keys in my '90 stepper with the bars cranked around an inch since the late '90's. put a add-a-leaf (big mistake) in the back to level it & i run 285's x 16's (33 x 11.5) with no rub even off-road. in the 16 or so yrs with keys & cranked bars, i have replaced both cv's, pass one twice, snagged a log & broke it, & last fall i finally changed the 25 yr old stock ball joints/control arms.
the truck has NEVER driven weird, ride rough, wandered, even with a 1/8" of slop in the old ball joints. the truck goes off road quite often & my biggest complaint is the lack of wheel travel with ifs, constantly skying the front tires. mind you, i'm not a thrasher off road though, super low gearing & slow speeds gets me just about anywhere i need to go
unsafe, dangerous, bad for the truck?, after all these yrs, thats not even on my radar, ifs are not as fragile as people belive. i still prefer the solid axles in my toy, but ifs has been a great DD, off-road driven every day truck for me
check out this read on ifs, kinda interesting


IFS SURVIVAL: PRETTY BASIC REALLY!


Is IFS as strong as a comparable straight axle in overall axle torque rating?

Yes. The biggest reason for IFS failure is lift kit manufacturer insufficiencies in testing and trail use before the
lift kits are released to the public! Many Manufacturers drop the front diff inappropriately creating increased
CV angles at their claimed lift gain, leaving the cv's at their greatest operating angle with the wheels straight. If
the steering is turned a little, the outer cv's are beyond their operating angle, and disaster is at the next turn!

Can IFS handle more high speed abuse and jumping than a straight axle?

Yes. This is common knowledge in the off road world that when it comes to speed and suspension abuse IFS is
king! It's pretty straight forward when you think about your suspension moving over bumps! On an IFS truck the
largest amount of weight changing direction is your front tires. On a straight axle, most of the weight cycling up
and down is the entire front axle, so this weight moving rapidly under the vehicle creates extreme harshness
making the vehicle uncontrollable at higher speeds. In many cases a 1 ton front axle with large tires may weigh
more than the frame and chassis, so you know who's gonna win the smoothness battle here!! Not the Chassis,
but the front axle!! This will take a toll on electrical wiring, radiators, hoses etc. Lets say this is an example of
50/50 weight ratio. Most IFS weight Ratios are more like 95/5. Pretty easy to see why IFS rules here! It also
goes to reason that if you put a 1 ton straight axle under a small vehicle it is alot more dangerous at speed!

Do Some IFS lift kit manufacturers, cheat by not lowering the front diff. Adequately?

Absolutely! Don't want to mention any names, but many lift kits that claim 6" of lift only lower the front diff
3.75"s! This increases your CV angle 2.25"s. Basically the only safe amount of lift would be ~ 4"s on these
particular kits. When a truck is lifted, normally larger tires are going under it, so not lowering the front diff to
OEM specs is a ticking time bomb for the CV's and front diff!

Is the 1/2 ton GM/AAM 8.25 diff just to weak to be a contender with SAS (Dana 44)?

Yes, we have found this to be true!! For whatever reason the AAM 8.25" by weight and size ratio is very
insufficient when compared to the AAM 7.25" that is under the S-10's, or the 9.25" under the 8 lug 2500-3500
trucks! We have found that the 8.25" is only capable of handling only 7% more axle torque than the AAM
7.25", and can handle only 63% of the axle torque that the AAM 9.25" can!! (Realift testing) Maybe gas
mileage and efficiency won when it came to the 1/2 tons! If you have a 1/2 ton get the 9.25" in it or be careful!!
Without a locker available we performed all testing on the 8.25" with it spooled. We found that the cases
surprisingly survived much better when locked than with open diffs. The side pinion gears acted like a wedge's
stretching/spreading the 3rd members making the aluminum case more prone to breakage! Aluminum cases
do not hold up well to the shock loads of an open diff or unlocked 3rd member when severe differentiating
occurs! We would recommend to always have the differential locked when putting extreme loads on the AAM
Series ICA's

Is the AAM 9.25 diff as strong as a 99-08 3500 1 ton Dodge truck in terms of axle torque?

Yes, with a good lift kit that is installed correctly this statement has been proven! As it turns out they are
basically the same axle, 1 is an I.C.A. (Independent Carrier assembly) and 1 is SAS (Solid axle suspension)
These axle's both share most of the same 33 spline axle parts.

Is it's OK to crank up the torsion bars to get fender clearance to prevent tire rub?

Never, this is the silliest thing that an individual can do to their truck. Here's why!! When you crank the torsion
bars you didn't just raise the truck you weakened your CV strength and steering strength. The reason it is
harder on the cv's and the steering isn't just from the extra angle, but more from the increased load on
your tire at any given angle of the suspension cycle, which means more traction and load at the more
dangerous angle. At the oem operating angles the suspension supports the entire weight at this given angle,
and the cv's and steering system can handle tons of abuse because the load on the cv and steering
decreases as the wheel extends. For Example: If the wheels are all the way drooped/extended in OEM form,
there may only be 250-300 lbs of load on the tire so it's nearly impossible to put a tremendous amount of strain
on the cv's or steering because the suspension loading is too soft. Crank the torsion bars up and now you may
have up to 1,000 lbs of load on the tire with the wheel drooped/extended. Potentially 4 times more force with
the cv's and steering angles at there most vulnerable point.

What about the Red sled in Peterson's? What happened here?

The red sled for starters used the weakest 9.25" front diff of all G.M. trucks the 88-96! The 97-08 are much
better. Lots of extra reinforcement has been added to the aluminum cases and better axle heat treating
processes. The red sled was obviously an example of many things stated above! The front diff was not
centered, this is terrible, because the cv's will both work incorrectly. 1 side bottoming in the tripod joint and the
other trying to pop out of the tripod joint. This is hard on everything. You cannot break 2-3 cv shafts and
expect not to do some damage to the (ICA), which ultimately happened. I have never broken or seen any 9.25"
cases break the way the red sled case broke. (1) I have a feeling that the drivers side case half had worn
bushings therefore making the passenger side half handle most of the torque. (2) The drivers side cv shafts
bottoming on the tripod joint put to much side force on the right hand case, and (3) I also think the 3rd member
support bearings may have been to tight also. (4) When the case broke the front locker was not engaged,
which would make it more prone to break a case.
It may not make sense to an old time SAS guy, but it's true! So basically they proved all of our historical
facts in just a few articles and a few issues, just not how to fix them! I think it's sad that they stopped
prematurely on the sled. 1-2 more article's and they may have really turned some heads!

Would the installation of a front locker just destroy IFS front cv axles?

No, on an IFS setup the locker actually helps it survive, mostly because the wheel with the most traction
happens to be the wheel with the better cv and steering angles. It also reduces the force at the extended wheel
dramatically since the wheel with the most traction is the one most apt to do it's job. Normally with an open diff
the wheel that is extended or drooped takes all the axle torque which is exactly what you don't want.

I hope this has alleviated a lot of the war on IFS/SAS.

If your truck is set-up correctly breakage should only occur on the cv axle shaft or tripod joint, although these
failures can ultimately destroy a case half. We have broken alot of stuff over the last 7yrs. During the first 3
years of this testing we destroyed countless #'s of cv axles, cases, driven axles and steering components with
just minor to moderate wheeling! Since we have learned all of the things stated above this is what we have
broken in 4 more years of Severe Rock Crawling:
7.25" with 35" tires (3 S-10 cv axle shafts, 1 Tripod joint, 1 Aluminum Case while reversing)
8.25" with 35" tires (7 1/2 ton cv axle shafts, 2 LH stub shafts, 2 Cases broken from tripod joint interferences
and broken stub shaft interferences)
9.25" with 37" tires (Nothing after our most severe testing yet) Just for the heck of it we delivered full throttle
power to just 1 front axle the drivers side then the passenger side with a 1993 200 HP 4.3 litre in low range in
1st gear equipped with 4.88 gears and no breakage occurred! The 7.25 failure occurs at about .25 throttle the
8.25" Failed just under 1/2 throttle!

http://realiftsusp.com/IFSsurvival.html

[Mike C]

Great info. Thanks for taking the time to put that out there.

I elected to keep my '02 Duramax at stock height but I did increase tire to 265 70 17. The amount you have to raise the truck and (In my opinon) concessions you make aren't worth it for the amount of increased tire size you can get. So I just tow my wheeler with the truck. :-)

In reading about the Duramax diesel IFS trucks, they abuse the heck out of the front diff either drag racing or sled pulling and have very few difficulties with the Eaton E-Locker in the front.

And the torque the modified trucks put down is just unreal.

[special-K]

Thanks for the input. All I have is real world experience as an original owner of a '92 K3500 SRW that worked every mile it was owned weighing 8,000+ pounds driven off road regularly and often towing a trailer. I cranked the torsion bars at 20,000 miles, ran 285/75s, ran it 335,000 miles and only had to replace the idler arm every 80k and nothing else. In the 22 years I ran it, everyone I talked to said it was typical of all trucks like mine to have the idler arm go bad that often when running bigger tires. It was never an issue replacing that and 80k is a lot of miles on any front end part. I don't believe you can lift a truck more with keys than with cranking torsion bars. We are talking 88-98 8-luggers here. The limiting factor is the a-arm suspension. lift keys advertise 2" lift, with one claiming up to 3". I lifted my trucks 2" with cranking and we all know if you want 4" you have to go with the drop brackets. Why would anyone spend what the 4" lifts cost if they could do the same with keys for a small fraction of that cost? It would seem you could install the keys to get the 2", then crank the bars another 2", but once again the limiting factor is the a-arm travel

[Mike C]

This is one of those case where your sample size is small with just 1 truck. Your experience worked out OK which is cool, but others do have problems doing the same thing.

I know that you are an experienced mechanic and would recognize if something was way out of whack and that combo worked well on your truck.

And remember that GM used different keys depending on the package the truck was equipped with so it worked fine with the key you had but might not with one of the other key combos.

I think some of my front end parts are worn out now and I am at stock height on my '02. The IFS steering (and once again, my truck is not the same vintage as yours) is known to wear out some parts (like the idler arm you mentioned) much faster than the solid axle trucks.

But I have no issue with the IFS trucks and really like mine. But knowing that changing even some of the geometry can accelerate wear mine stays stock. (Makes hooking and towing the gooseneck a heck of a lot easier too!)

[61K10]

I cranked my 2k 1500 z71 up some to level it some, but still has a small rake to it. rides a little firmer than before.

[special-K]

Originally Posted by Mike C

This is one of those case where your sample size is small with just 1 truck. Your experience worked out OK which is cool, but others do have problems doing the same thing.

I know that you are an experienced mechanic and would recognize if something was way out of whack...

Don't short change me, Mike. I've had TWO!
I don't consider myself a mechanic. Just a guy who has done what he could to fix up and keep running whatever I've had. I like to understand how what I use works, if nothing else.

I didn't intend to start a thread asking a question so I could disagree with the replies. Especially with you. It's obvious you have full circle understanding of drivetrain & suspension. My '90s trucks have been work trucks with only mild changes while my older trucks were always my toys. They've been driven where a 4wd was required, but I don't go 4 wheelin' and take them to the limits. I can see where if I used keys, then cranked some more I would be at one end of the limits when the sweet spot was intended in the middle. I never heard of keys till lately. There were never any lift keys offered the first 10 or more years I owned the '92. When I ordered my truck we went through every option and there was no plow package that I saw or any other suspension option. I did get the off road package but I saw no mention of enhanced suspension as a feature of that. IIRC, something was changed from prior years where adjusting torsion bars had just become possible. Could be wrong. Never had anything from 88-91. I think I'm good with where the Suburban sits now, about 2" up. I think it's about where I had my '92. i don't see any benefit to buying lift keys if the same issues can occur. My intention with starting this thread was to see why this shop owner would say they tear things up when they don't lift any more than I cranked mine. I've heard of others having to replace stuff and considered myself lucky...or they weren't as easy on their stuff as I am. When the truck was on order in '92 I was fueling up my '84 and a guy with a newer IFS truck was saying I better hang onto my truck because those new suspensions were crap. He had already had CVs replaced and something else. I started worrying I made a mistake getting one. It came in and I drove the wheels off of it for 22 years with original CVs...go figure. I've had enough lumber on my racks to depress the front end enough for the tires to rub and towed with enough tongue weight to lift the front end up enough to clear 35s ().
It may have been the communication I had with this buddy was a bit off from what that shop owner had said to him. My buddy gave me the impression he was told the keys will do harm that cranking won't, when the shop guy was probably saying you still risk the same issues with cranking. My (young) buddy is the type of guy who wants to put a solid axle under his Suburban to drive to work. That used to be me, but I'm more practical now and feel the IFS is just right for it's intended use, like other factory things some guys like to rag on. I use mine as intended...with a slightly larger tire, that's all.

[Mike C]

I completely get that. I'm too cheap to lift mine anymore, I hate replacing parts! Carry on...

[special-K]

I'll let you know how my Suburban holds up.

[BigRed76]

When I had my '95 6 lug K2500 for a brief time I considered doing the lift keys too. So just out of curiosity I cranked up the torsion bars to see how far they would go and I was able adjust them enough to max out the travel of the upper control arms. The angle that it put the upper ball joint at was terrible, and I didn't leave them that way, but it did prove to me that lift keys weren't necessary.

[special-K]

Here is my '92 the way I had it, with 255/85s: