Side gears, spider gears, cross shaft, thrust washers and clutch plates to rebuild a 31-spline Ford 8.8 Traction-Lok rear that chatters or no longer locks.
This kit rebuilds the inside of a Ford 8.8 inch Traction-Lok limited slip carrier with 31-spline axles. If your F-150, Mustang, Explorer, Expedition, Ranger or Crown Victoria rear end chatters in tight parking-lot turns, clunks on and off the throttle, or spins one tire on wet pavement like an open differential, worn clutches and tired spider gears are the usual cause. Instead of buying clutches in one box and gears in another, this set replaces the whole internal stack in one go.
It cross-references to F88CPK, ZIKF8.8-T/L-31 and USA-16017.
The Traction-Lok is a clutch-type limited slip. A clutch pack sits behind each side gear, and a preload spring between the side gears pushes both packs against the case so some torque always reaches the wheel with more grip. The 23-spline outer hub of each side gear drives the frictions, while the steels lock to the carrier. As the frictions glaze and lose thickness the preload drops, and eventually the axle acts like an open diff. When the friction modifier in the gear oil breaks down, the plates stick and release in steps, which you feel as a shudder or chatter in turns. Chipped spider gear teeth or a grooved cross shaft give a metallic clunk when you go from coast to drive.
Try the chatter test first: change the gear oil and add the correct friction modifier. If the noise goes away, the clutches may still have life. To check lockup, raise both rear wheels with the transmission in Park or in gear and turn one wheel by hand; a healthy Traction-Lok resists, while a worn one spins freely with the other wheel turning the opposite way. Pinion bearing whine that rises and falls with speed is a different problem; a full 8.8 master overhaul kit covers bearings and seals instead.
The 8.8 inch 10-bolt rear was used under the F-150 from 1983 through 2014, the Explorer and Explorer Sport Trac, Expedition, Ranger from 1999 to 2010, the Mustang from 1994 to 2004 and 2006 to 2014, Crown Victoria, Grand Marquis, Town Car, Mountaineer and Navigator, among others. Not every one of those axles has 31-spline shafts, so count your axle splines before ordering. This set does not fit the 12-bolt Super 8.8 used from 2015, and it is for Traction-Lok carriers, not open differentials. If you want help confirming, send us your year, VIN and the axle tag code. You can browse more 8.8 parts in our rebuild kits section.
If you want Ford's own shim set and modifier in the box, see the Ford Performance M-4700-B clutch kit. A new steel 8.8 diff cover is a good upgrade if yours is dented or leaking.
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| Cross reference | |
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No. The side gears have 31 inner splines for 31-spline axle shafts. Count the splines on an axle shaft before ordering.
No. The 2015-up Super 8.8 uses a 12-bolt cover and different internals. This set is for the earlier 10-bolt 8.8 Traction-Lok.
Usually not. The cross shaft, spider gears, side gears and clutch packs come out through the cover opening once the axles are pushed in and the C-clips are removed. That leaves the ring and pinion setup undisturbed.
Use 75W-140 synthetic gear oil plus Ford XL-3 friction modifier for a Traction-Lok. Add the modifier first.
Try a fluid change with fresh friction modifier first. If the chatter comes back, or one wheel spins freely, the clutches are worn and the full kit is the better repair.
A clutch-only kit replaces the frictions and steels. This set adds new side gears, spider gears, a cross shaft and thrust washers, which is the right call if the rear also clunks or the gears show chipped or pitted teeth.
