Is the FX4 Level II a Locking axle?

heavy breather · Apr 27, 2017

Is the rear axle in a FX4 Level II a limited slip, or a true locker? If its a true locker, what do I need to get the locker to work? Is it computer controlled, or is it basically the same as any other E-Locker?

It seems to me that for $500 plus freight ($150-200) for a bolt in part, seems better than buying a aftermarket 31 spline locker and an explorer axle that needs new perches and shock mounts. Or am I missing something here?

fastpakr · Apr 27, 2017

Mechanical limited slip (Torsen).

heavy breather · Apr 27, 2017

That's not surprising, Its listed as a locked axle. But with the listings, locked and limited slit are the same.

Captain Ledd · Apr 27, 2017

Do you currently have a 31 spine 8.8?

Honestly, unless you're turning big tires (35/36+) with a lot of power, the regular 28 spline does just fine. Then you can just buy a regular locker (Ox, ARB, or E-locker) in the 28 spline version, and use your current axle (again, if that's what you have). Most of the time you won't need to re-shim the carrier, but have the means to check the backlash if you decide to do it yourself. If the backlash is what you measured before, you're good to go.

But, it is a limited slip. A very nice limited slip, but a L/S none the less.

RonD · Apr 28, 2017

This page is a good one to bookmark: http://www.therangerstation.com/tech_library/index.shtml

It's the Tech Section for TRS

Has an AXLE section with Locker info

An OPEN differential will send torque/power to the easiest axle to turn, so once a wheel/tire looses traction and spins it gets ALL THE POWER, lol, but they are the least expensive to build and install

Limited Slip uses equal rotation to divide the torque, if one axle starts to spin faster than the other the clutches or gears in the differential give the faster axle less torque, so opposite of OPEN.
Ford's Trac-Lok(and GM's Posi-traction) uses clutches, Torsen uses Gears, so a little better than clutches, which was why it was used on the Level II's

Locking differential mechanically locks both axles together, so they must spin at the same speed, torque is equally divided to both axles.
This provides the best traction but also doesn't allow going around a corner because the inside wheel must turn at a slower speed than the outside wheel, so outside wheel will skip/drag to match inside wheels slower rotation, this will break something in high traction situations, i.e. dry pavement

So a Locking differential will have an ON/OFF mechanism, it can be mechanical, but most are either electric or vacuum operated from in the cab
They can't be "automatic" since that would defeat the purpose, Limited Slip are "automatic", so an automatic Locker would just be a Limited Slip, lol.

When off road, or low traction situation and traveling more or less in a straight line you would Lock the differential for best traction, small differences in wheel speed wouldn't matter too much because it's a low traction situation, so a wheel could skip/drag without breaking anything

heavy breather · Apr 28, 2017

I undertand how they work, my limit is my look up software and my personal knowledge about the options on the rangers. My look up software considers limited slip and locking diffs the same thing. So unless I personally know what options were available for a given application, I have no way of knowing. And most of the counter guys at the dealers around me don't know either. All they can tell you is what will or won't work based on part numbers generated by the VIN. So even if it's a direct bolt in option, they won't know. My soft ware is slightly better in that it will at least tell me about non exact stuff that will bolt in with some minor changes.

I am concidering the 31 spline because I will be towing a bit with it also. I don't see my self running bigger tires, but next year I plan on getting the 4" superlift so I don't have to be so easy on it while off the pavement. I can either pick one up now for $355.00 delivered, or I can wait until I get one in stock and pretty much just have it. Bad thing is, rangers are expensive at auction, so we're not likely to see one any time soon.

gw33gp · Apr 28, 2017

I think one of the main advantages of the 31 spline axle is; it uses larger diameter wheel bearings. This is very good for towing and heavy loads on long hauls. I tow my race car all over the country with at least 800 lbs on the bed. I also do a lot of over-landing off-road with heavy load in the bed. I had almost 200K miles on the original rear wheel bearings before I had the differential gears changed to 4.56. They installed new wheel bearing as part of the install. The old bearings were still in good condition and there was no groove worn in the axle where the bearings ride.

My experience with the Torsen shows it almost acts like a locker when accelerating. This has proven to be very useful to me over the years of off-roading with it. The torque bias is also higher than with a typical clutch style LS. I have learned to not accelerate very hard when turning sharp corners on pavement because the inside tire wants to screech due to the Torsen trying to rotate both axles at the same speed. Another advantage of the Torsen is; it doesn't wear like a clutch style LS and has very little (if any) drop off in torque bias over time.

heavy breather · Apr 28, 2017

gw33gp said:
I think one of the main advantages of the 31 spline axle is; it uses larger diameter wheel bearings. This is very good for towing and heavy loads on long hauls. I tow my race car all over the country with at least 800 lbs on the bed. I also do a lot of over-landing off-road with heavy load in the bed. I had almost 200K miles on the original rear wheel bearings before I had the differential gears changed to 4.56. They installed new wheel bearing as part of the install. The old bearings were still in good condition and there was no groove worn in the axle where the bearings ride.

My experience with the Torsen shows it almost acts like a locker when accelerating. This has proven to be very useful to me over the years of off-roading with it. The torque bias is also higher than with a typical clutch style LS. I have learned to not accelerate very hard when turning sharp corners on pavement because the inside tire wants to screech due to the Torsen trying to rotate both axles at the same speed. Another advantage of the Torsen is; it doesn't wear like a clutch style LS and has very little (if any) drop off in torque bias over time.

Thanks for the reply, with the exception of the towing a race car, it sounds like I will be using my Ranger in a very similar fashion as you.

Is the FX4 Level II a Locking axle?

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