Many people believe that a 4x4 truck sends power to all (4) wheels when it's in 4x4. That's usually not true. Generally in a Ranger the power is sent to the right rear wheel. If the truck has a limited slip, it will divert power to the left rear wheel when it feels the right rear wheel start to slip. The same holds true with the front axle, except the power is generally sent to the left wheel, and then diverted to the right.
A locker allows power to be sent to both rear wheels (or both front if in 4x4). There are (2) types of lockers, (1) that is engage permanently using compressed air or electric, and the type that engages power to both wheels when you apply power to the differential (mashing the go pedal!).
A locker is a must for any serious offroad enthusiast. You'll need the locker to send power to both wheels to get the best traction.
As mentioned, there are different types of lockers:
(1) An air locker solidly locks the rear end together using a small air-compressor attached to a locker in the differential. The advantage is that you can switch between an open and locked differential instead of having the locker engaging and disengaging.
(2) An electric locker. Similar to above but is controlled electrically instead of using compressed air.
(2) A spool (Not Recommended) solidly locks the rear axles but should only be used for off-road competition since it doesn't let the axles turn at different speeds while cornering.
(3) A Lincoln Locker (Same as spool) is simply welding the spider gears in the differential together.
(4) A Detroit locker replaces the whole carrier and unlocks when turning.
(5) A Lock-Right is the most popular because it replaces the existing spider gears, unlocks while turning, is affordable, and doesn't require setting up the ring and pinion like a Detroit Locker would.
Axle trusses are something that you can add to your axle to protect it from bending during serious off-road use, Especially if you like jumping your truck. Desert racers in particular should have one of these because getting airborn is "normal use" for them. For most people, the additional strength added by a truss is cheap insurance against damaging an expensive axle A slight bend in an axle tube will quickly wear out the axles shafts and bearings. It may also damage the differential itself as well as cause distinctive wear to your expensive offroad tires. And of course, serious bending of the housing can cause the axle to break leaving you stuck somewhere.
You use to be able to find bolt on axle trusses. They were typically a heavy metal rod that ran under the axle tube between the leaf spring perches and had a plate welded to it that sat under the differential (skid plate). They were held on with u-bolts near the spring perches along with a strap that went over the front of the differential housing. The problem was that they hung down and would catch on things sacrificing ground clearance.
Eventually people began fabricating trusses that welded right to the top of the axlehousing.
The truss shown above left is made by T & T Customs and is designed to be welded on to the top of a Ford 8.8 (above right).
Adding larger tires requires the use of lower (numerically higher) gears. To figure out what gears you need after a tire size change, click HERE.
If you really want a 9-inch rear axle you can swap in one from a late 1970's Lincoln Towncar which has a width of 57-inches. The spring pads will have to be relocated to the top of the axle and the driveshaft will need modified to accept the larger U-Joint. Currie Enterprises (714-528-6957) can custom make a Ford 9-inch to your specifications.
8.8-Inch Axle History:
Ford began using the 8.8-Inch axle in Rangers circa 1986 on "incomplete vehicles" aka "chassis cabs" (as mentioned above), but the 8.8" axles only became common in Rangers with the introduction of the 4.0L V6 in mid-1990. It began appearing in Explorers (and Mazda's Navajo twin) in 1991. It has also been used in 4.0L Aerostars (2wd
ONLY, the 4.0 AWD Aerostars, strangely, are equipped with the 7.5-Inch axle), From mid 1984-up F-150 (Except for 5.4L "Lightning's" and Some 4x4 Supercabs which are equipped with the heavier-duty 9.75-Inch rear axle) 1984-1/2 on Full-size Broncos, and E-150 Econoline vans.
The 8.8 is also used in other Ford products such as Mustangs, Thunderbirds ("solid axle" 1987-1988 with 2.3 turbo engine and 5.0 "Sport" models), Crown Victorias and their equivalent Mercury and Lincoln products. However, because of their different suspensions, they make undesirable choices for swapping into a Ranger (unless you're looking to also swap to a four-link rear suspension for airbags and such).
(Independent Rear Suspension) version also appeared in the 1989-1997 Thunderbird, Mercury Cougar, (Though there is also a 7.5-Inch IRS
in some V6 cars), the Lincoln Mark VIII and finally a very similar IRS
suspension was adapted for the Mustang Cobra.
A wide range of gear ratios is available, from 3.08's up to 5.13's. An equally wide array of differentials is also available from open carriers to limited slips to lockers and spools.
8.8" axles can have either 28-spline or 31-spline axles.
All car applications use 28-spline axles, all truck applications use 31-spline axle shafts EXCEPT Rangers, which use 28-spline axles. However, even exceptions have exceptions......The 1999+ Ford Ranger FX4 come with the 31-spline 8.8-Inch axle and 4.10 or 4.56 gear ratios.
Gear sets are interchangeable between axles, regardless of the spline count. Differentials, however, are not.
The axle above in an 8.8-Inch from a 1995+ Ford Explorer. You can quickly identify it as an Explorer axle due to its rear disk brakes and the spring perches mounted below the axle tube instead of on the top. When swapping an Explorer 8.8-Inch axle in to a 4WD
Ranger you need move the spring perches to the top of the axle tube.
What Comes With What?
Width is same as other pre-93 axles, 28 spline
3.08 (4x2), 3.55, 3.73 and 4.10 (4x4) factory ratios
Either limited slip or open differential
10" drum brakes
Width is same as other 93+ axles (1.5" wider than pre 93), 28 spline
Ratios and differential options as noted above
Width is same as other 93+ axles, 31 spline
4.10's and Torsen limited slip from factory
Width is 1.5" wider than 93+ Ranger, 3" wider than pre-93, 31 spline
Spring perches must be fabricated and welded on top
Stock spring perches can be used to lower the truck (like a flip kit)
Shock mounts must be fabricated and welded on
Very common to find ltd. Slip, usually 3.73 or 4.10 (4x4) gears
Same as above, also has rear discs
How To Spot A 7.5-Inch and 8.8-Inch Axle:
It's pretty much all in the differential cover. Obviously all rear axles in Explorers are 8.8-Inch, but Rangers could of had either a 7.5-Inch or 8.7-Inch. Note the difference in the covers below:
Ford 7.5 Differential Cover
Ford 8.8 Differential Cover
View Exploded Axle Diagram
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