Hey guys- got a bug in my head to put a limited slip in the 8.8 in my '92 F150. I'm sure someone has taken the center section from an explorer or something like that- who's done one, and what does it take?

 

I'll be following this discussion as well.
I was just going to swap mine out for one from the junkyard with lower gearing, but not against doing the whole thing myself either. And a limited-slip, while not a necessity for me, would not be a bad thing either.

Paul

 

Changing out the diff will require installing your ring gear on the new diff,installing at the proper preload and checking back lash and pattern. Removing and adjusting until correct and then final install. Pinion depth shouldn't be affected, but it could be.

 

Gotcha. I'm gonna have to look into specs and procedure on that one, it's the first diff I've ever really done.

 

I see you are in Colorado. Is winter / snow driving an issue for you? If so I'd suggest rethinking a limited slip. I will say that a lot of people disagree with me on this and I'm not saying they're wrong. But living in MN I have a fair amount of experience driving on snow and ice, so I'm not wrong either.

In my experience a clutch-type limited slip is the worst possible choice for winter driving. The clutches need to slip for the tires to go different speeds, so even coasting around a corner you are using up some of your precious traction just to force the diff to work. That makes it relatively easy to swap ends when there isn't enough traction to slip the diff so it starts scrubbing a tire. Once a tire is sliding it doesn't care which way it slides so it tends to slide sideways.

Having a limited slip set up really loose will reduce this effect, but it also reduces the limited slip's effectiveness. And in my experience there's no sweet spot. The factory limited slip that was in my '97 F-250 when I bought it at 161K miles was so worn out that it would spin a single back tier on wet pavement, but it still had me sliding sideways while coasting around a corner on packed snow.

If you need better traction in snow, better tires an adding weight over the rear axle will go a lot farther that changing your diff.

And if you really think you need a traction-aiding diff I'd recommend either a Truetrac or a locker over a clutch-type limited slip.

I have a Truetrac in my '97 now. I can't say I love it because with one tire on ice and the other on pavement it's not positive enough to reliably get you moving from a stop, but it still will spin out if you get on the gas too hard. (Any working traction-aiding diff will have that tendency. But I can live with that since I can control it by staying light on the throttle. I can't live with swapping ends because I was coasting around a corner with a clutch-type limited slip.) I'll still keep the Truetrac, and I definitely like it better than the worn out clutch-type limited slip that gave worse stability while giving worse traction. But if I was doing it again I might choose an open diff (for better stability) or a locker (for better traction).

An automatic locker isn't for everyone. They will swap ends on you faster than just about anything if you get on the gas too hard, and sometimes "too hard" means "at all". Still, they don't try to scrub tires when coasting, so they don't hurt stability unless you're on the gas too hard. I've driven one through more than 10 Minnesota winters and wouldn't hesitate to do it again. But they definitey aren't for everyone.

A selectable locker is sort of the best of both worlds: locker traction when you need it, open diff stability when you don't. But they are expensive, and when locked it's a spool, so you need to turn it on and off at the right times. Not that this is impossible, but it's not as simple as an open diff, a Truetrac or an automatic locker.

 

I'd have to agree with pretty much everything Nothing Special said. Traction devices in the diffs can be treasure or terror! Which is why the selectable lockers are such good choices sometimes. Once you get past the initial sticker shock, if possible!
The Truetrac can actually be fooled into sending torque to both wheels, just like many limited-slips, by gently applying the brakes to slow down a spinning wheel. But just trying to get yourself out of a rut on generally flat ground is one thing, while doing all this in a sketchy situation can be a different matter altogether.

Sometimes in a 2wd truck you feel like you don't have much choice though. Either moving forward with the help from both tires, or spinning just one and sitting there halfway helpless. Making you long for that push button on the dash to lock 'em up when needed.
Funny, but I bought one of the first ever ARB's for a 9" back in the '90's when I worked at a 4wd shop and the ARB guys gave us a good deal on some for our own use. But they recalled the first-gen units before I had a chance to install it. And by the time the new version was released, I couldn't afford it anymore!
So I'm still ARB'less after all these years.

But I have a Detroit Locker in my Bronco that can be amazing, but also means I would NEVER consider driving it to the mountains when there might be snow or ice. Got a Truetrac to go in it's place though, so after that I might be convinced to experiment a little.
Being a flat-lander and a city-boy from sunny climes, I'm not well versed in ice.

Paul

 

I've got to admit up front that I've never tried the e.brake trick with a clutch-type limited slip. But knowing how they work I've got to say I don't see any reason the applying the e.brake would make the diff transfer torque to the tire with traction. I can see how it might help you not spin the tires quite as easily because it takes more power to spin them. But that would work just as well with an open diff and has nothing to do with making the limited slip more effective.

However that trick DOES work very well with a Truetrac. Unlike a clutch-type limited slip that sends up to a fixed amount more torque to the tire that's not spinning, a Truetrac sends a fixed MULTIPLIER more torque to the tire that's not spinning. I've heard that it's 3.5x (or 2.5x for diffs intended for a front axle), but I can't confirm those numbers. But assuming they are accurate, in a rear axle the tire that's not spinning gets 3.5 times as much torque as the tire that is spinning. But if one tire is in the air, it supports 0 torque, so the other tire gets 3.5 x 0 = 0 torque. This is where the e.brake trick comes in. If you apply the e.brake enough to take say 50 lb-ft of torque to spin the tire that's in the air, then the Truetrac will send 3.5 x 50 = 175 lb-ft to the other tire. Of course the e.brake is applied to that tire as well, so you need to take away the 50 lb-ft it takes to slip the brake (which is why this shouldn't help with a clutch-type limited slip). But that's still 125 lb-ft that goes to moving the truck. So yes, the trick does really work with a Truetrac.

The thing is, most of the time that a 2WD truck is stuck it's not is a situation where one tire gets zero traction. Usually if one tire is in mud, so is the other. Yes, one tire will spin first so it LOOKS like only one tire is driving. But open diffs send the same torque to both tires, so whatever torque it takes to spin that tire is also going to the tire that's not spinning. And if that amount of torque (2x what it takes to spin a tire) will move the truck, it'll move.

When the truck won't move with an open diff, if you were to lock a selectable locker, how much help would you get? Often not much. If both tires are in mud it maybe takes 10% more torque to spin the second tire, so then you'd only get 5% more "push" with the locker engaged than you'd get with an open diff. People expect twice as much because they hear "an open diff is really only one-wheel drive". But it's not, an open diff really is driving both tires.

A traction-aiding diff can help a 2WD vehicle a lot when one tire gets no traction. Like when I'm stopped at the stop sign three blocks from my house, trying to start up a slight hill with my right tire on ice and my left on bare pavement (that's how that street always ends up...). But other than situations like that, a traction-aiding diff really doesn't help a 2WD truck much. That's why I say good tires and weight in the bed is a better bet.

 

https://www.ford-trucks.com/how-tos/...rential-360784

I watched this the other day. As I would like to go to a 4.10 some other day...

If only I had the time and money to match my desires. Lol