The Advance Adapters Tx2 Heavy Duty Dual Bearing Crawler Kit (part number 50-5905D) is a gear-driven crawler adapter designed for the 1979–1995 Toyota Truck gear-driven transfer case with a 21-spline input. The improved double bearing design provides enhanced gear support and reduces deflection compared to the original single bearing design.
How It Works: The Tx2 adapter installs between the transmission and the transfer case using the front section of the Toyota transfer case as a donor box. The installation takes the stock Toyota transfer case from a standard low gear ratio of 2.28:1 to a crawl ratio of 5.20:1. The adapter casting is only 2.375" in length to minimize overall driveline length increase. Driveline and floorboard modifications are required when installing this unit. An extended speedometer cable will also be necessary since the transfer case is relocated further rearward.
Transfer Case Identification: This kit fits Toyota Truck 21-spline gear-driven transfer cases. The 21-spline transfer case has a male 21-spline input shaft and can be identified by 7 bolts attaching the tailhousing to the transfer case. For 23-spline gear-driven transfer cases, use kit 50-5906D instead.
Construction: Adapter housing is manufactured from 356-T6 heat-treated aluminum alloy for strength and light weight.
What's in the Box:
- Tx2 double bearing adapter casting (51-5909)
- Double bearing coupler — 21 spline (52-5909)
- Special stud bolts (716065)
- Spacer (716182)
- 1/4" steel ball (716182B)
- Sealed bearing 209RS (716308) — qty 2
- Needle bearing for crawler adapter (716323)
- True arc snap ring (716456)
- Tx2 crawler snap ring (716463)
- HiLux transfer case gasket (716563)
- Toyota truck transfer case gasket — 1984 and up (716564)
- 10mm × 1.25 nuts, flat washers, lock washers
- Adapter instructions
Note: Syncro dogs (911069) are sold separately — 3 required per unit.
Fitment: 1979–1995 Toyota Truck — 21-spline gear-driven transfer case (Toyota Truck RF1A).
Part Number: 50-5905D