My 2004 XLT 4.0, AT, 2WD Ranger REALLY NEEDS a limited slip rear axle. The truck is like new, runs perfectly, I want to keep it and the only thing the original owner did not put on the option list was a limited-slip rear axle. Can't imagine why not! Can any of you guys tell me the easiest, least expensive way to accomplish the swap? I do NOT need a beefier setup, just limited slip. I've changed lots of rear ends over my many years so am not unfamiliar with the process. What I need to know is where do I find the gear ratio, and what years/models/etc. are interchangeable. And one other thing, are stock Ranger limited-slip rear axles generally durable and do they perform well? If I buy a used one, is there anything I should do to it before installing it?

 

If you want reliability, I'd go with an Eaton TrueTrac differential

 

Yeah, that would be really sweet. But it kinda stretches the concept of "least expensive!" Summit gets like $430 for the unit and then I'd have to have a qualified shop set it up for me. I can R&R a rear axle, but I've tried setting up the gears and bearings in differentials with not much success. Matter of fact, I've had limited success finding pros in the business who can set up a differential and not end up with issues, mostly ring-and-pinion clearance or carrier bearing noise. At this stage and for this truck, I need to just replace the axle. Were I 50 years younger and still in the serious hot-rod-truck-in-the-dirt phase of my life, I'd go for the Eaton in a heartbeat!

 

All Rangers with 4.0l engines have an 8.8" rear axle

Most 4x4 models came with Trac-Lok, Fords name for Limited Slip, GM calls their version Posi-Traction

You can find your axle type and ratio on the drivers door sticker
Look here: Ford 7.5 & 8.8 Inch Axle Tag & Door Codes

And you can use the same codes to find a limited slip axle at wrecking yard.
R6 code is most common, 8.8" 3.73 ratio Limited Slip
Any 1998 to 2009 Ranger axle will bolt into your 2004
1997 and earlier will as well but they are 2" narrower

2010-2012 will bolt in but you will need different u-bolts, these did have disc brakes so may be worth the extra trouble

Swapping the whole axle out is the least complicated
remove brake lines, e-brake cables
ABS sensor
Drop drive line
Remove u-bolts

Ranger axles were never a known problem, so a used axle is a fairly safe bet, but used anything is always a gamble



Swapping out just the differential/carrier can be quicker if you feel comfortable with the adjustments needed.
You would keep your ring and pinion gears and just remove the Open carrier and replace it with the LS carrier

You have a 28-spline rear axle if you are looking for these

Yes, the Detroit/Eaton Truetrac is a good choice but not cheap, $400-$500, but nothing good ever is, lol.

The Ford Trac-lok carrier can be picked up used or rebuilt and is also a good choice for 2WD use

 

WOW! Thank you so much for the detailed info. Everything I need to know! One question comes to mind now: since the axle assy I'll hunt down will most likely come from a 4x4, what are the chances of finding a 3.55 ratio out of a 4x4? Did the automatics use 3.55's? I do not want to change that since I do 75% highway and it works great for that. And getting 20+ mpg. I live in the boonies and not having the LS has been an issue many times, especially in winter!

 

I don't think there is any listing for how many Rangers came with which axle ratios
We know 3.73 was the most common

3.73 won't be much different that 3.55 on the highway, but not the same

You can adjust actual ratio with tire size.

Look here: Gears needed after adding larger tires

Say you have 3.55 ratio now, and you install a 3.73 ratio

And you have 28" diameter tires now

If you were to use 29" diameter tires that would change the actual ratio to 3.60, so very very close to 3.55

And you're back to what you had

You know what you have so plug in the numbers and see what will be best for your needs, you have to RESET that calculator each time

3.73 could drop down to a 3.48 with 30" tires, if you had 28" before

If you just have the tire size not diameter there are sites you can look up tire diameter using the size


An old trick I learned many many years ago from my grandfather
Open axles send power to the wheel that is EASIEST to turn, so once a wheel starts to slip it gets ALL the power, lol, WTF who the heck design that

If you hold the E-brake release handle out and slowly press down on e-brake pedal it will grip the spinning wheel harder than the non-spinning wheel making the spinning wheel HARDER to turn which transfers power to the OTHER wheel
Got unstuck many times with this
Very very hard to do with manual trans, lol, but a piece of cake with automatics

 

Thank you again for even more great assistance, and thank you for your Grandfather's great tip! Sometimes us gearhead Grampas aren't appreciated enough for our accumulated lifetimes of usable wisdom!

So now begins the search. I've already found like two dozen L/S axles locally but every one is a 4.11. Still looking, though!

Cheers!

 

Is it possible to add a LSD to the open differential in the 2004?

 

Yes, its easier to swap out the whole axle assembly for most people, 1993 thru 2009 rear axles will work in a 2004 model

But yes, if you are comfortable, or want to learn, how to setup pinion and ring systems then there are a few options you can chose from that are a little better than the Ford Limited Slip(L/S)

Ford and GM L/S use clutch packs that can/will wear out, but they work as well as others
Torsen L/S used gears so outside of breaking, it won't wear out

 

that’s strange bc I have a 2010 ranger xlt 4.0 4x4 5 speed, and it has firstly with a 7.73 even tho it’s a 4.0, and it’s 4x4 but is a simple open diff.

 

Yes, its odd that 2010 didn't even have a Limited Slip as an option, 2WD or 4x4
2009 did
2011 did

2010 was the first year for rear disc brakes so maybe they didn't have any L/S rear axles available yet?