Long Travel IFS

I have been kicking this idea around on and off for awhile, and been seriously thinking about it for a few weeks and talking to my dad and my offroad buddies. This will be a long post, so bear with me.

As it is me, I would do a custom long travel IFS. By that I mean, custom A-arms and spindle, maybe shock hoop.

I have read this thread a lot: http://www.froum.ttora.com/forum/showthread.php?t=183890

Another guy did a SAS on a 3rd gen, and then he went back and ripped it out and did a custom LT. He had to reinstall the front differential, so he swapped out for a skinnier one and all custom fabricating (since who goes from SAS back to IFS). He doesn't have any engineering experience, but got it working and working pretty good too from the sounds of it. I am majoring in Civil Engineering with an emphasis on Structural, and my dad is an expert at Structural Engineering, so with his help I could definitely do all the engineering (like with my sliders) and analysis. Especially if some guy with no experience but intuition can do it, I'm sure two structural engineers can make a custom LT IFS strong enough.

Now, this is still very preliminary which is why I'm throwing this out for you guys too judge. If I decide to do this, I will do a solid CAD model of my current IFS and to figure out how it is loaded, and then design my LT arms around that with added margins obviously. The design would theoretically be almost a direct bolt on, so the truck won't have a long down time during the work. Bolt into the stock A-arm locations, with frame fabricating probably need for the shock hoop/rotating the current upper shock mount. This is assuming I would even need to do that, I could always leave the shock location and either get larger coils or bump my 5100s height, which either one would be needed because of the longer lever arm of the wider LT arms would put more force on the coilover in the same location. Anyways, the plan would be to get it fully modeled and analyzed so I could install it over Christmas break probably.

Now for WHY I want to do this. Well for one, I think it would look cool. Terrible reasoning, but nonetheless I personally like the look of long travel setups, just knowing that you can go as fast as you want over almost anything. Now for actual performance reasons, the truck will sit wider obviously (I'm kicking around 3" wider per side). That's a major point though, wider is worse on tight trails, but is 3" per side really that bad when the truck is pretty skinny already? It would also make it more stable is the counter argument (which I'm very conscious of after rolling). Once tuned or setup, I believe my ride quality will also increase on road let alone offroad it would perform beautifully (I am thinking of shooting for around 12-14" of travel). My 4runner is setup pretty generically right now, and I don't want to put it as a designated rock crawler. I want it to be more of a recovery vehicle, and good in the snow, and I like to go fast (since that's what IFS is good for, but I also just like prerunners over rock crawlers). On that note, I think since the suspension would be improved, it would do great at speed but it wouldn't do worse at crawling or anything else, probably better but not by much. Another reason, is I think a custom suspension would be awesome and I want to do more fabricating on my truck. Another reason is I could easily stuff larger tires since they would be nowhere near the frame or fenders, though this doesn't matter as much as I don't plan to go past 33s and I should be able to fit those fine already.

So another point, the back end of the truck will NOT be drastically changed, if at all. I would maybe go to a taller rear coil that is softer (Land Cruiser), just since my back end is pretty stiff now and potentially the front end would sit an inch taller or so. However, I won't have increased travel, or at least right away. So the truck will be setup in the front similar to a prerunner, but it will really be like a pre-prerunner. I don't want to invest $1500 in fancy coilovers for the front yet, or modify the back end a lot since this alone would take all winter break to build, but I think it would make the truck handle a lot better for how I use it. I don't intend to go over giant jumps or anything anytime soon, but I want to be able to cruise down a rocky trail or road with a lot of potholes and stuff at 30mph without worrying about bottoming out if I hit a bump and the front lifts up a bit, which is common the trails around here.

The next topic is fender flares. My front left fender should be replaced eventually already, so may as well get the larger fenders and go this route if that seems logical for the truck. I had a buddy who mentioned a tubed fender, which I can't find a picture of nor ever seen but know what he's talking about: take a tube bender and bend a tube around then coat it in sheet metal and blend it into the stock fenders. Regardless, that's probably one of the biggest cost issues, since a fiberglass fender set is ~$500. Similar to this, is I was thinking of widening the rear end, maybe just with spacers which I have read of people doing though not sure if I like the sounds of that...since it will be abused that extra 3" lever arm might be too much for rough trails. Though I was talking to a shop yesterday, and they said they haven't ever widened someone's rear end to match the front. I could always do an axle swap or get wheel spacers and then larger offset/backspaced wheels to push the tires out; the main issue is fenders again, since I would have to bolt onto the truck since that's where the body is so I can't buy fiberglass fenders for it. I would also have to enlarge my wheel well (or the fender part where the body is on the back) since the wheel would stick out and have too much up travel and hit the body (maybe). Though that's a secondary issue/future project.

Hopefully this made some sense since I don't want to proofread, and was kind of just spitting out my thoughts and am in a rush. I'm just wondering what people's thoughts are and if I am missing anything/should think about anything before I get more commited. I'll also ask around on T4R.org later on if you guys can't convince me not to do it.

What are you going to use for CV shafts?

If I were going to put a custom longtravel in the front of a 3rd gen, I'd a) adapt an 8" axle housing to use in the front with custom half-shafts and 1st/2nd gen CV shafts/spindles, or b) just find a way to make a Tundra front diff and control arms fit.

I really like the idea of using an 8" housing.  Cut each side short so it fits between the frame rails and lines up with the front driveshaft, then cut and respline a pair of rear axles to use as half-shafts.  Then use stock 86-95 CV shafts and spindles between custom control arms.  The only non-factory part you'd might break would be the half-shafts, and you'd get the awesomeness of a drop-out third member in front.  This was a project I was kicking around for my '86 before it died, I'd love to see somebody go through with it.

There must be CVs with the same spline as the 8" diff though right? Cause I agree that would be sweet. The guy at the shop I was talking to was also saying it's a bitch to regear my front end because it's a clam shell diff or something, so it's really time consuming (not sure if that's true or not). I was thinking of using T100 CVs like the 3rd gen/1st gen taco kits are designed for. I would rather not do custom CVs, just since if I break one I will most likely not be at home and able to remake some, they need to be off the shelf.

Could I respline the differential to the CVs splines? Then I would just pull the front differential, stick the new one on and weld a cage in for it, then bolt on the new arms. I'll have to look at how hard that would be to do, and I would need a 3rd member waiting to drop in when I got home so I can crank ass to get it built and ready to drive to school 3 weeks later...If I could find an e-locked 3rd member from a runner or taco then I could get a locked front end in the process...

You wouldn't happen to know the width of the 8" member and that of the stock front diff? Since if it's narrower I'd gain travel obviously...

Yeah, the clamshell diff is a PITA because you have to put it completely together to check clearances.  Then take it apart again, adjust, put it together, etc.

I don't know of any CV shafts with the same diameter and spline count as the 8" diff.  That's why I'd cut down a pair of axles for half shafts, and then use those earlier CV shafts, because they aren't splined on both ends like yours are.  You'd have the halfshaft coming out of the diff, and then bolt the CV up to the halfshaft.  And yeah, that way you're using off the shelf parts.  Your halfaxle would be custom, but that CV is going to break way before the stub shaft will.

Early IFS CV shaft:

Why would you want to swap out the diff besides regearing anyways? Is it stronger?

It's stronger for sure, and it'd give you the benefit of having a dropout third in front and cheaper gears and lockers, and best of all you'd have the only 8" IFS diff in the world.