GM IFS: What actually breaks?

[WrenchMonkey]

New-to-me tow rig is an 02 Suburban 2500 with the big 8.1.

I've developed an incredible itch to crank up the torsion bars and stuff a set of 35s under it. Combination tow rig and light-offroad puppy-bus.

I know the IFS isn't exactly the hot ticket on the trails, but I assume the 2500 stuff is stronger than the half-ton, and this would only be rutted-dirt-road type of wheeling.

The worry is, this IS the tow rig. If/when it breaks, it has to be fixed to get it home.

So, what breaks, and how field-repairable is it? I assumed it was mostly CV half-shafts. Carry spares, swap em out, not so bad. Or, since they flange-mount to the diff, can't you just unbolt em and drive on in 2wd?

Doing a little research, I guess the streering linkage is fragile too. I can change out the steering on my XJ in about 15 minutes flat. Is the Burban stuff as easy?

Anything else? Any experiences?

Thanks all!
:beers:

Robert

[Jonesy]

I know the biggest issue from being around the local diesel pulling trucks, is the tie rod ends and associated components. Under a hard load in 4wd the wheels will toe in several inches. There are several companies that offer upgraded components specifically for this issue. Other than that the only other upgrade the pullers do is a locker in the front. Not sure how that abuse correlates to the abuse we put on them off road.

[93 Krawler]

I don't know the differences between a 1993 and 2002, but I put my 93 IFS through hell. I never broke a shaft. I did bend the tie rod, so I welded a small angle iron on it. If I can make it through rail bed in Harlan, I'd say you should be ok doing light off-road.

I had to put a 6" lift on mine to run 35's. I would assume your 3/4 ton sits higher than my 1/2 ton did.

I would upgrade the steering components and put the biggest tire you can fit under it without raising the torsion bars. My .02...

[biggin69]

X2 on the torsion bars. It will ride like hell if you crank them up.

[underpowered]

most bend/break Tie rod ends. CV shafts can break, especially on cranked TB's.

If one breaks you can swap it out, or carry a spare stub shaft to get home in 2wd. just like your XJ, they use unit bearings and rely on the hub nut to hold it all together. if you pull the shaft, good chance your unit bearing will fail on the drive home.

otherwise, not many real trail breaks i have heard of with the IFS.

however, if you decide to crank it, be prepared to replace ball joints on a regular basis.

you can fit 33's with only a little crank, that is the route i would go, 35's won't much it much better off road than the 33's will.

[WrenchMonkey]

I don't know the differences between a 1993 and 2002, but I put my 93 IFS through hell. I never broke a shaft. I did bend the tie rod, so I welded a small angle iron on it. If I can make it through rail bed in Harlan, I'd say you should be ok doing light off-road...

That makes me feel better. I won't be doing anything like that.

I had to put a 6" lift on mine to run 35's. I would assume your 3/4 ton sits higher than my 1/2 ton did.

I would upgrade the steering components and put the biggest tire you can fit under it without raising the torsion bars.

I think I can fit a 33 as-is, with just a little rubbing. I know if you crank the bars all the way (like 3" lift) the ride goes to schidt. But I've read that an inch or two isn't too bad, and that might be all I need.

The upside is that if I crank it and hate it, I can always turn em back down.

I can fiddle with the lift, clearance and ride compromise. I just want to be ready for whatever trail breaks I might see.

Thanks for the insight guys!
:beers:

[Hope Springs Hauler]

Speaking from the "I have a 2500HD on 33s" viewpoint, there is some tuck n trim to the bumpers and wheel well liners.

The weak stuff is:
Pitman and Idler arms
Tie rods
Unit bearings wear prematurely

I've avoided popping halfshafts, but I don't do boosted launches or offroad it, just pulling trailers back to remote lots

[hotrod]

I drag race my lb7 and I have tie rod sleeves and straight center link to keep from the "duramax wave" when leaving the line under boost. Same concept as before. If I were to offroad it, I'd want at least tie rod sleeves. You can get them anywhere, but I suggest merchant-automotive.com they are good people.
I also lowered mine 2/3 to get the cv shafts straight in the front :evilgrin: hate on... :evilgrin:

Not my truck, but an example.

zrgToLQg7lI

[WrenchMonkey]

Yeah, I remembered this one:

_tKUDUkXjP8

(The H2 used the 2500 truck running gear.)

I guess the bonus with the sleeves is that you still use stock tierods. If they do break, or when they wear out, you get the stock part warranteed and reuse the sleeve.

Cool.

Robert

[blazerbrad]

Big difference between doing fairly hard rock crawling like the H2 above and pulling a trailer down rutted roads. I have an '03 2500HD with 132k on it and my dad had an '02 2500HD with just under a 100k when he sold it. Mine has spent a decent amount of time in fields and minor off-road stuff including pulling trailers around in 4 low and has been stuck with the trailer several times also. Also beat on it quite a bit trying to get back up a dirt/grass path from down in a valley after a rain (multiple full throttle attempts, speedometer read 40 mph but truck was barely moving). Never have broke anything or even replaced any parts, but I am getting ready to go through the front end as routine maintenance. I also grew up in a farming community and worked construction and there were tons of IFS Chevy trucks running around that got used hard. My cousin, while he does a good job on maintenance and keeps stuff clean, is notorious for running the hell out of vehicles. His trucks spend almost every day in some sort of off-road condition and pull big goosenecks with construction equipment around during the week, and oftens spent the evenings and weekends working on the farm pulling wagons. He has never broken any IFS parts either.

Now I'm not saying these parts are bulletproof as if you put big tires, lockers, and try to run the Rubicon every weekend they will break. But for what these trucks are designed for (reasonable size tires, farming, construction, mild off-road) they work pretty good. In other words, for towing the off-road toy down unimproved roads and what I would expect for it to see off-roading (where a Sub can fit and not get torn up) I wouldn't worry too much.

For tire size we ran 285/75R16's (about 33x11) on the stock alloys on both the '02 and '03 with no torsion bar cranking but did require minor trimming in the front. This involved the plastic inner fenderliner and front valance. On my '03 I recently switched from the factory wheels to aftermarket 16x8's with the exact same size and brand of tires and started having rubbing issues. It's just on the plastic inner fenderliner and does no damage, but makes a lot of noise. So going from a 6.5" to 8" wide wheel with about the same backspacing made a substantial difference in how the tire fits when turning (arc is muc

Cranking the torsion bars in moderation is okay. The biggest thing that causes the horrible ride is when the bars are cranked enough the a-arms are resting on the droop stops, meaning when you hit a pothole the suspension can't drop down any. The higher the angle on the CV's the more wear and less total strength you have....biggest issue is the wear and especially wearing a hole in the boot as once the grease goes the joint will fail shortly afterwards. Tierods and balljoints are the same way as the more angle the more stress on them, plus add in the bigger tires that is generally associated with cranked bars.

Last year I picked up a set of 17" H2 wheels with 35x12.50's BFG tires and test fitted them on my '03. Personally I thought it was going to require too much work to make them fit (keep in mind I run 40" tires on only 4" of lift on my K5 Blazer so big tires/little lift and massive trimming is something I'm quite familiar with). Even by jacking up the frame and letting the front suspension droop to simulate cranking the torsion bars 2" the tire were not even close to being able to turn full lock in either direction without getting into hards parts (i.e. just not plastic stuff). I'm sure you can do it, and other people have, I just was not willing to bother with it. Part of the issue was I also did not want the power/gearing loss of the tires.