Rebuilds the Toyota 8-inch rear differential with Koyo carrier and pinion bearings, races, pinion seal, full shim kit and crush sleeve.
A rear-axle whine in an early Toyota 4WD pickup or first-generation 4Runner, or a regear on a later 4-cylinder truck with an aftermarket ring and pinion, both start with the same kit. This is the USA Standard Gear ZK T8-A master overhaul kit for the Toyota 8-inch rear differential with the 4-cylinder gearset. It replaces every bearing, race and wear item around the gears with Koyo bearings, so new or reused gears run on a fresh, correctly set foundation.
The ring and pinion are not included, and neither are the axle shaft seals. Bring your own gear set, or reuse the original if the teeth are clean.
The Toyota 8-inch is a drop-out third member axle: the whole differential unbolts from the front of the housing and comes out on the bench. The pinion rides on two tapered bearings held in preload by a crush sleeve, and the carrier spins on two side bearings whose shims set backlash and carrier preload. When those bearings wear, the pinion moves out of its depth and the gear contact pattern drifts, which is what produces the whine. Replacing all four bearings at once and resetting depth, preload and backlash puts the gear mesh back where it belongs.
With the rear raised, rock the pinion yoke up and down and in and out. Any felt movement means the pinion bearings or preload are gone. Drain the gear oil and look for chunks rather than fine paste. Drive on smooth pavement and note whether the noise changes with throttle or with speed, then spin each rear wheel by hand, because a dry wheel bearing can sound like a differential. Our differential whine diagnosis guide walks through these checks, and the master overhaul kit buyers guide explains what a full kit replaces versus a bearing-only kit.
USA Standard Gear catalogs the ZK T8-A for the Toyota 8-inch with the 4-cylinder gearset, 27-spline pinion, 1-1/2 inch pinion head and 45 mm carrier journals. That covers factory gears in the 1979-1985 4WD pickup and 1984-1985 4Runner. On 1986-1995 pickups and 4Runners it fits only when the axle has an aftermarket 27-spline ring and pinion with the 1-1/2 inch pinion head. Factory 1986-and-later gears use a different inner pinion bearing, which is why some installers find the bearing in this kit does not match what came out. Measure your old pinion bearing and count the pinion splines before you order. Rears with the factory electric locker need the 8-inch E-Locker master kit instead. Send us the year, VIN and the gear set you are running if you want a second check.
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Only if the axle has an aftermarket 27-spline ring and pinion with the 1-1/2 inch pinion head. With factory 1986-and-later gears the inner pinion bearing differs. Check your pinion splines and measure the old bearing, or send us your details.
No. The kit supplies the bearings, races, pinion seal, shims, crush sleeve, pinion nut, ring gear bolts, thread locker, marking compound and a gasket. You supply the gear set.
No. Toyota 8-inch rears with the factory electric locker use a different carrier and need the E-Locker master overhaul kit.
The kit maker specifies Koyo bearings and races for both the pinion and the carrier.
Revolution Gear lists 12-15 in-lb of pinion preload and 0.006-0.010 inch backlash for the Toyota 8-inch, with 70 ft-lb on the ring gear bolts and caps. Always confirm against the specs for your gear set.
