Had the gov lock in my old blazer. They use flyweights and springs and after pulling someone out in reverse, mine self destructed and locked the diff solid. I was able to buy the gear assembly and various small parts to repair it fairly cheaply but to me, it is a little frail for serious offroading

 

What is "TT"? I'm assuming you're talking about TrueTracs since that's the context, but people use too many acronyms here sometimes (for instance, what does "EB" mean? Early Bronco, Eddie Bauer or Eco-Boost, depending on the context).

Assuming you mean TrueTrac, I'm finally starting to get some real-world feedback on front TrueTracs in snow, and it sounds like they aren't as bad as I was concerned that they might be. I'll still maintain that nothing is as stable as an open diff (in either axle). If you want to gain traction you do need to sacrifice some stability. But a TrueTrac probably is better traction and less bad stability than a clutch-type limited slip. And real people in real-world use are saying that a TrueTrac is very acceptable in a front axle in snow.

 

Not sure if this thread is active anymore, but if it is, I think I might get an answer here...... I hope.

Here is the deal, I read through most of the thread, but being really stupid to 4x4, I have not much of an understanding to the technical merits of the post.
Perhaps if you could dumb it down to a level of telling me what happened yesterday in my new (to me) 2011 F-250 FX4.

A friend of mine just had his house built.
Its on a few acres.
The house sits above the paved public street.
His driveway, about 400 feet, or so, runs uphill to the house.
They had that put in too.
They had to grade and fill it, as the terrain is not flat, etc.
Removed big evergreens, and so forth.....
The natural earth was interrupted.
They put down gravel on it, not pea gravel, but bigger.
It has been raining alot, like it does in the Pacific Northwest.
He asked if I could drive my truck on it to help pack it down.
I thought, heck yeah....
Going down was easy, coming back up, nope....
Couldn't do it.
The wheels on the driver side just dug in.
I tried 4 low, real slow, nope, same result.
I didn't know I could lock the real axle by pulling the **** out, so I didn't try that, would that have helped?
I assume that locks both rear wheels in place to turn regardless of traction, if one slips?

Why does the "truck" not sense a wheel slipping and shift the traction to the wheel that isn't?
If I read all the stuff right it seems to give the slipping wheel more power, is that right?

Thanks

 

sounds to me like they just put the stone down and did not compact it. anything will get stuck in loose stone.

 

As Tom said, climbing a hill with loose rock is a real traction challenge.

I'm not sure what **** you're talking about. And I'm not familiar with 2011 trucks. There are some newer trucks that have locking differentials (usually a selectable locker). I wasn't aware that Ford ever offered it, but if they did and yours has it, then yes, engaging it would typically lock both rear tires together so they turn the same speed regardless of anything. Not great for turning corners, but it might have helped you get up that hill.

Most factory differentials are "open". That is the cheapest and safest (no handling quirks) differential available, so no surprise it's the most common. Open diffs send the same torque to both sides, so if one side spins with little torque, it sends the same little torque to the other side as well. If the net result is that you don't get enough traction to move, then the one tire spins and the other sits still. Since power equals torque times speed, the side with traction is at zero speed so it's getting zero power and yes, the slipping wheel is getting all of the power. It's not that the diff is trying to give more power to the tire with no traction (it doesn't know anything about power). It's just giving the same torque to both sides and that's what happens.

To actually sense a slipping wheel takes wheel speed sensors and a computer. Traction control systems do that. They typically don't involve the differential, instead they apply the brake to the spinning tire. Since it takes more torque to spin it with the brake on, the open diff then sends more torque to the tire with traction. It sounds like your truck doesn't have traction control.

There are diffs that won't spin the wheel with no traction as easily. They don't really "sense and shift" anything, they just are designed to do something other than the equal torque of an open diff. Earlier in this thread I described how clutch-type limited slips, gear-type limited slips, automatic lockers, selectable lockers and the Eaton M-locker all do that, so I won't go into it again.

 

Bob, on the 2011 and newer Super Duty trucks, pulling out the ESOF 4X4 **** engages an electric rear diff locker.
very nice feature.

 

The newer f150s and Superdudys have a rear e-locker option and if your f250 has that then yes it would have helped if you engaged it.

 

I just wanted to post an update on using front and rear TrueTracs:

I had the chance use it in 4x4 high on some dirt in Baja and my initial impression was that the steering was a little heavier but nothing that would compromise safety or hinder you in any way.

Then we (in Minneapolis) got the "wintery mix" weather come through on Monday night. And by that I mean frozen cake ice topped with some snow. By the time I ventured out on Tuesday, the roads of the neighborhood were bad. Every car I saw at my intersection was spinning its wheels. Initially, I didn't put it in 4 hi. I got a little wiggly making a left on to Lake Street but it gathered up easily. 4 hi was engaged and it was like the ice went away. I didn't perceive any tendency to pull to one side as one side of the truck rolled off the 2" of ice onto wet pavement and then back again. Then I was trying to break traction. Which was possible and fun.

Now I'm looking forward to the next round of winter weather to go play, er, I mean drive in a safe manner because my truck is equipped with superior mechanicals that enhance my safety factor.

And when that happens, Bob, you are welcome to get some 1st hand experience with a TrueTrac diff in the front of my truck.

 

I think that Autolockers and Lunchbox lockers need to be two separate posts, or categories. They function completely different. Most Lunchbox lockers expand when the pin torques the center carrier halves apart and then locks up. Getting them to unlock for a turn while on the gas, by jumping off the gas, can be tricky.

The Detroit and Yukon ratchet unlock on their own, much smoother. It's center and pins are one solid piece. The Detroit and Yukon are the only ones I call "Un-lockers".

Lockers are also one of my favorite subjects. If I can make it this winter, without using 4wd on the street, or my rear locker on the street, then I'm putting a Yukon Grizzly locker in my front axle. (I already have the OEM Elocker rear) If I do need to use 4wd in a blizzard at speeds less than 20mph only, then it's still on.

I'm pretty certain that I can go more hardcore for mud and beach, while sacrificing on road snow 4wd use.

I want max grip and auto operation for ditches, mud, beaches, pulling boats up a sand ramp. I hate how ARB's are nearly useless for pulling boats up a sand ramp. They won't allow a turn like a Detroit will.

 

I have front and rear spartan lockers in my Jeep and they do great on and off road. When we get snow I usually only use 4x4 at lower speeds on snow covered back roads then I switch to 2wd when I get to the main roads that have been plowed. The front locker doesn't cause any problems. I also like an auto locker in the front for offroading better than a selectable because it is easier to turn whereas with a selectable you are always locking and unlocking it and they don't always engage/disengage when you want them to, an auto locker is always there and always working when you need it.

 

I'm glad it won't be a problem. It'll be a nice bonus if it's OK in snow.

I definitely like the auto lockers better than selectable for exactly that reason. That doesn't mean I'll pull out the OEM one though.

 

That would be great! PM me on the board here!

 

They mechanically do different things, but the net result is that they work almost exactly the same. I've had both in rear axles (only a LockRight in the front) and really haven't noticed any significant difference in performance.

But you touch on a common misconception of auto-lockers when you say:

You do not need to get off the gas to get auto-lockers to unlock. If you are going around a corner and the outside tire has enough traction to roll rather than skid that will unlock the locker. (If the tire doesn't have that much traction, then there's really no way to "unlock" any locker, but then again, even an open diff would be sliding the tire in that case, so it's no worse than that.)

You may need to get off the gas to turn, but that's not to get the locker to unlock, it's to get the tires to stop spinning or to get rid of the torque steer from the inside tire trying to fight the turn. To the extent that auto lockers make it hard to turn, it's because they do unlock easily (and only driving the inside tire), not because they don't unlock.

 

It's been a while since this thread has been active. Since then I've installed a selecable locker in the front axle of my Bronco and a TrueTrac in the rear of my pickup. I've had time to get some real-world experience so I thought I'd share it here. I'll cover the front selectable here and the rear TrueTrac in another post.

Front Selectable Locker
I chose an air-actuated OX locker for the front of my Bronco. I liked the OX for the mechanical internals (vs the ARB or any of the electric lockers). But I chose the air-actuated OX because it seemed easier to mount a small valve in the dash (more like a switch really) and run an air line than it would be to mount a lever and run a push-pull cable. Plus my Bronco already had on-board air. (For people unfamiliar with the OX, it uses a shift fork in the diff cover to engage and disengage. A push-pull cable to actuate it is standard, but you can also add an air- or electrical actuator too. Since it uses a custom diff cover to mount the shift fork you can't get one for a TTB or a 9"). And by the way, in choosing the OX I'm not saying anything bad about any others. I had to make a choice and this is the one I made. I'm happy with my choice, but I may well have been happy with a lot of others as well.

Most of the time it's unlocked so it functions just like an open diff, which is great. I've only locked it in the rocks, and I really like it there! The locked front crawls over rocks much better than an open diff of course. I was a little concerned about how hard it might be to steer when it's locked. Most of the time it isn't a problem, because most of the time when it's locked there isn't good enough traction on both tires to make it a problem. So I've been able to lock it when I think I'm going to need it and just leave it locked until I don't need it.

I will say that steering it when it's locked and you get good traction is pretty hard, especially if you're sitting still. One tire needs to roll forward while the other rolls backward when you turn the wheels while stopped. The locker obviously doesn't let that happen so the steering is HEAVY. Also it will jam up in the "locked" positions at times. I flip the switch and if it's loaded up it won't unlock right away. But so far it's always unlocked after sawing the wheel back and forth once or twice, so that's been easy to live with.

Overall I'm really happy with this choice!

 

Rear TrueTrac

I've had the TrueTrac in the rear axle of my '97 F-250HD CCSB through one winter now. Jumping to the end, I like it, but not quite as much as I thought I would. Most of the time it's completely invisible, which is great. And most of the rest of the time, when an open diff would be just spinning one tire, it does what it's supposed to and drives both tires.

But there have been a significant number of times when it's not enough. Most of the time that's when starting with one tire on ice and the other on pavement. It's never kept me from getting going (which an open diff would've done), but it was much less effective than an automatic locker would've been (which I have more experience with). And if I'm on the gas a little too hard going around a corner it'll kick out the back end at least as easily as an automatic locker.

So in my experience it's less effective than an auto locker (no surprise there) but no more stable than an auto locker in snow. Overall I think I prefer a rear automatic locker to a rear TrueTrac for winter driving.

I'm still not sorry I went with the TrueTrac in this truck though. As I said before, I don't think that auto lockers are the best choice for a truck that tows heavy trailers, and I want this truck to be good for towing. And auto lockers require you to pay more attention to the truck. I don't mind doing that, it's a small price to pay for the performance I value. But I don't feel great about letting just anyone drive a vehicle with an auto locker, and my two grown sons both borrow the truck from time to time. So I think the TrueTrac was the right choice for this truck. But I was hoping to not have found it's shortcomings quite so often.