IFS + Front Locker Article...informative!
 

Here is a good article on the topic (for the hardcore owners!): http://www.4wheeloffroad.com/techart...als/index.html

I have copied the article just in case 4WO decides to erase it: (2 posts)
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Front Locking Differentials - Locked & Loaded
Front Locking Differentials For Your IFS
By Jerrod Jones
Photography by Jerrod Jones

Thinking of putting a front locker in your IFS 4x4? Oooh...that's a toughie. Bet you have a lot of questions, huh? We can probably incorporate all these into one main question, and we can come upwith a very vague answer for you as well: Will an IFS front end hold up to a locker? And as for our vague answer: Well, maybe. Yeah, that reply is weak, but there really is no definitive answer for this one. Different applications, different styles of driving, different vehicle uses, they all factor into the future of your differential.

Your psycho neighbor isn't going to be running on the trail very long before he breaks his locked 7 1/2-inch Toyota front end with his 42-inch tires. But how about the guy who plows your driveway that only engages his selectable front IFS locker to gain traction when there's too much snow mass to push? He'll probably tell you he's never had a problem. Why is this? Why are many consumers so scared of IFS lockers, and what do they have to worry about?

Those are some big questions to answer, so we better get started.

And if you're asking for our personal advice, we'd probably tell you to stay away from full lockers in independent front ends, and maybe stick a helical-gear limited slip in there instead.

When IFS started coming out on fullsize trucks more than 20 years ago, they were almost automatically dismissed by the heavy-duty crowd, with claims of weaker parts than the solid-axle predecessors. We and a few other magazines certainly didn't help matters either at the time. Adjectives like "crappy" and "weak," names like "junk," and new definitions for what IFS meant were about all anyone could write regarding this better-riding, better-handling front end. What guys (and girls) like us tend to forget is that we are the minority consumer in the automotive market. Most owners of IFS front ends would actually prefer this setup over a solid axle. Even though the independent front ends tend to be weaker than the solid-axle counterparts, they do work well in most conditions for most drivers.

But we are not most drivers, you and us. We are extremists that will push a 4x4, IFS or not, into situations that would probably not be considered safe or intelligent by most people. And when we do this stuff, things break. Yes, IFS is generally weaker than a solid axle, so the scare of a locker in an IFS with 35-inch tires is real. But then again, we wouldn't feel good about a locked 10-bolt solid axle with larger than 35-inch tires either

Ha! What don't you have to worry about? You're thinking of putting a locker in a front end that is even named after things moving independently! And now you want to lock something up there together?

It turns out that some people have had a little luck with lockers in IFS front ends. Toyota IFS owners seem to have the most success (at least in the U.S.) with lockers in their differentials. Their 7 1/2-inch ring-gear setups combined with the light weight of the truck seem to work out if staying with a reasonable tire size (read: 37s max!).

1. Steering Have you ever watched a fully locked IFS truck climb a troublesome hill? If you haven't, let us tell you it is a scary thing to see. Many times you can watch the front tires move violently in and out as their tie rods deflect. This is due to tire pull and weak tie rods. The locker locks the two tires together, and they both want to pull straight ahead. When the suspension oscillates, the tie rods toe in or out, which now is making two spinning tires either pull towards, or away from, each other, wanting to rip the front end in half.

Now some aftermarket companies are offering beefed-up tie rods made from rod ends and DOM tubing for IFS trucks. This will certainly help.

2. CVs The CV shafts are a constant worry on IFS trucks. Will they break, will they pull apart, will the angle become too great as the suspension droops? Hard-core users are breaking CVs without lockers, and now you want to put twice the amount of stress on those shafts? Well, again, this is something you can address. Companies like RCV Unlimited and Rough Country have replacement CVs for a number or trucks, or if you have a Toyota you could look at upgrading to bigger Toyota (T-100) shafts. IFS is not the end of your truck, it just takes a little beefing (just like any solid axle) to make it perform in the dirt.

3. Differential Housing Though most people think the CVS will blow first, the differential housing is also something to worry about on some IFS trucks. Some of the housings are made out of aluminum, and the pressure of the pinion gear trying to deflect from the ring gear can possibly crack or explode the case. We've seen it happen numerous times before. For this, there really is no fix besides a mega-bucks custom IFS housing, so break out your Gold Card. Either that, or just be wary that this can possibly be an issue.


You probably already know what we'd prefer in a stock IFS front end. But then again we'd probably say this about many stock solid axles as well; they could possibly grenade if not for beefing up the shafts, the steering, and other parts.

A limited slip provides a great enhancement in traction, without totally locking the two front wheels together. This can be beneficial on two levels: The enhanced traction of a limited slip is a plus, and the fact that one tire will stop if caught up on something can better ensure you won't hear a snap from underneath. There is a problem with clutch-driven limited-slip differentials in IFS though, where the clutch-driven limited slip will constantly want to pull forward, more so even than an automatic locker that would disengage around a corner. This will make steering input difficult to say the least. The best alternative you have for an IFS front would be a helical-gear-type limited-slip differential that will free up and allow you to carve a steering wheel back and forth.

A locker, on the other hand, provides the absolute best traction possible, and if you're in a real bind with almost enough traction, then a locker will pull you out of a situation, no problem. But a locker demands that both tires are spinning at all times, so if there is a lot of tire spinning, there will be steering deflection as they catch and pull. If one tire suddenly stops spinning, carnage is going to occur.

If we were building a multipurpose off-road IFS truck, we'd start the front end by upgrading the tie rods, then the CV shafts, and then think about adding the locker. We know that this probably isn't the way some people would end up doing it, but then again some people probably like wrenching on their junk, on the trail, with 10 trucks behind them, all cursing the driver and independent front suspension.

Gotta disagree.

I wheel with several guys who flog the he!! out of their locked IFS rigs in the rocks.

Blown CV's = lots, broken Tie rods = 0

My guess is that not all tie rods are created equal. For example, you hear Hummer H2/H3 tie rods breaking all the time, yet you hear much less in a Toyota. I think that the article deals the the general aspect of locker + IFS on your average vehicle.

That a good read , thanks for posting it. Good general info.

[COLOR=blue]My guess is your partially right. I would think tie-rod loading would go up exponentially with tire diameter and weight. 32's or 33's would require way less tie-rod than 35's. When you add the weight factor, especially of the H2, it almost makes sense they'd break. All the more reason to have a mid/small SUV w/32-33's rather than some wide monster that can't fit down the trail:D

If money was no object I'd love a locker in the rear and a Tru-Trac Torsen for the front. A Torsen helped out by ATRAC would be phenomenal IMHO

There you go, Toyotas are better than your average vehicle.

CJ3Flyr, you would think that H2/H3 tie rods would be built to size...that is, GM would design a tie rod to match H2's power and weight. Oh well, can't rely on logic these days! :D

The 2003 and up 4Runner and The FJ have a 8" front IFS and larger CV's.
Which should be stronger than previous years.

Yeah, but the newer SUVs have bigger engines and more weight....

+

So anyone thought about retrofitting the newer axle into the older rigs?? Is this possible, then u could easily run a locker in most situations

I think that it is easier to buy an aftermarket axle made for a 3rd gen instead of trying to retrofit.

You mean like just doing a SAS??
Or is there an aftermarket IFS upgrade for the 3rd gen?

I don't know...but if there is one, then it is likely cheaper than retrofitting a 4th gen IFS into a 3rd gen.

I was the first person to put an ARB RD90 in a 3rd Gen 4Runner IFS. That truck is still running today with no breakage on 33"s and a Supercharger. That is a 7.5". The spiders were the weak point in the 7.5".

Here is an article I did years ago. ARB Air Locker for Toyota IFS

It is also running an RD23 in the rear which is no longer made. I was the one who figured out it would fit in the third Gen back in 2000.

I also helped ARB figure out RD111 for the 4th Gens.

Driven properly, locking diffs will prevent damage that will occur without them. I'd be happy to offer tips. Retrofitting a 4th Gen 8" into a 3rd Gen 7.5" truck isn't worth the effort. Better to SAS at that point but the 7.5 is strong enough if cared for. The 8" also had some mount breakage issues. Not sure if Toyota fixed that. Guess I'll find out now that I have a 120.

The tie rods on the 4th Gen are thinner thann the 3rd Gen ones.