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Old 08-13-2008, 01:56 PM
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DaveInDenver DaveInDenver is offline
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Join Date: Jun 2006
Location: Larimer County
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Everyone lists the IFS as a con. Here's some random thoughts on the subject from your friendly neighborhood delusional owner.

From purely a crawling aspect, IFS takes a third row seat to a solid axle. But don't believe the Internet wisdom completely. It can work fine and doesn't take a lot to make passable.

The key is add a rear truss and a beefed up idler arm of some sort. Add low profile bump stops and away you go up to about 31" tires. If you want to run 32" or 33" tires, install ball joint spacers.

NEVER RUN A BRACKET LIFT! At least on a truck you intend to wheel. If 35"+ tires are the goal, just do the SAS. Bracket lifts are usually at the root of cracked frames or broken front diffs. Just too much flex in the sub frame.

The 7.5 front diff is fine in the application. It's less overwhelmed in this application than a 8" is in the front of an 80 series. The outer CV joint is just as strong as a solid axle Birfield, although the inner CV joint does need to be limited to how far you push it. When they say the max angle on the inner joint is 22 degrees, that's a hard limit. There's not a lot of margin in the travel on that joint. Within it's range of motion, it's fine, pushed to the limit of it's travel, it will break.

In some ways the IFS trucks are better. Other than the idler it's got significantly better steering, for one. The IFS trucks, even the 4 cylinder, have better brakes. But the IFS V6 brakes are about as good as any brakes on any truck.

It's when you go to 33x12.50 or taller tires, then IFS is simply over matched and there's not much you can do to work around it. But my suspension cycled reasonably well on the Rubicon and I have much too stiff torsion bars. No CV grenades, no broken ball joints, no blown tie rod ends. What I DID break were leaf springs...

The 7.5 inch diff has an ARB Air Locker, True Trac, Lock Right, EZ Locker or the Toyota Supra limited slip available. It's not really an issue, most people are gonna do an Air Locker or LSD in the front anyway. If someone does a Lock Right, they eventually do the ARB...

Isaac's truck does pretty good in the rocks, too. It's all about bounding the build. Stick to 33x10.50 or smaller tires, IFS is pretty easy to make reliable, although it will never flex as well as a solid axle. OTOH, they ride nice on dirt roads and highways. So it's trade-off.

The 3VZ does not make much more power than a 22R-E and is generally regarded as second class. I personally have never owned one, but have always thought it got a bad rap, Rudy's seems to last OK and he is not kind to his motor. Shrug. The reason in my mind to get a 3.0L truck is that they are easier to swap to a 3.4L if that's what you want. Otherwise, embrace the slowness and opt for the 22R-E.

So there you go, representing for the IFS posse. I think for whatever reason, everyone's convinced that IFS is junk and it's not. It has a limit and it's not easy to go way beyond those limits. You can lift a solid axle truck 4" or 6" pretty easily and fit 35" or 37" tires, where as 2" is about the limit with IFS and so that makes 33" tires is pretty much the maximum.

The main way to significantly improve stock IFS is a long travel conversion. This is no cheaper than a SAS, but does achieve a lot of the same goals. It has advantages over a SAS, primarily in ride quality on less improved roads and will hold it's own on many technical trails. Still, it's not quite a substitute for an SAS. But having 12" of wheel travel makes them attractive.
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