Motive Gear 3.90 ring and pinion for the Toyota 8.4-inch rear differential in Tundra, Sequoia, T100 and Tacoma pickups.
This is a Motive Gear 3.90 ring and pinion set for the Toyota 8.4-inch rear differential, the housing Toyota put under its larger pickups and SUVs. It crosses to Revolution Gear & Axle T8.4-390 and Yukon Gear & Axle YG T100-390. The 3.90 is the common regear target when 33s or 35s have killed the throttle response that came with the factory gearing.
Fitment covers Toyota Sequoia 2001-2007, T100 1993-1998, Tacoma 1995-2015 and Tundra 2000-2006 with the 8.4-inch rear axle. Measure the ring gear diameter before ordering rather than trusting the model year - Toyota mixed the 8-inch, 8.0 V6 and 8.4 housings across overlapping years and trim levels, and the gear sets do not interchange.
Install this as a full axle setup. You want new carrier and pinion bearings, a fresh crush sleeve or a solid spacer, and a pinion seal on the bench with it. Pinion depth comes off the shim stack behind the pinion head, backlash off the carrier shims, and you confirm both with marking compound - a centered pattern on the drive side that carries slightly toward the toe on coast. Set pinion preload with the bearings dry-fit first so you are not fighting a crushed sleeve on your third try.
Break the gears in gently: short drives, full cool-down between them, no towing for the first few hundred miles. Refill with the gear oil weight listed on the axle tag, and add friction modifier if the housing has a limited-slip carrier.
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