- (1) 23 or 21 Spline Coupler
- (1) Adapter Plate w/ Bearings Installed
- (1) Bearing Spacer
- (11) Studs, Nuts and Washers
- (1) Drain Plug w/ Aluminum Washer
- (1) Rear Transmission Output Seal
- (1) 2.28 Shift Knob
- (1) Snap Ring
- (1) Shifter Keystock
- (1) Detent Plug
- (1) Paper Gaskets
- (1) Instructions
- ⅜ Ratchet
- 12mm, 14mm, 30mm Sockets
- Air Wrench
- Needle Nose Pliers
- 3/16 Diameter Pin Punch
- Snap Ring Pliers
- 6mm, 10mm Allen Wrenches
- Gasket Scraper
- Flat Blade Screwdriver
- Adjustable Wrench
- Blue LocTite
- Axle Grease
What is the difference between 21 and 23 Spline Gears?
The transfer case input gear is the gear that slides into the transmission. V6 and turbo transmission use a 23 spline gear that is slightly larger than the 21 spline gear used on 4 cylinder transmissions. On a single transfer case you must use the gear type that matches the transmission. If you are building a dual transfer case assembly, the front case input gear must match the transmission output gear. The rear case of a dual transfer case can be set up with either 21 or 23 spline gears. When purchasing a dual transfer case adapter you can choose to purchase a 21 or 23 spline version. The only difference between a 21 and 23 spline dual adapter is the coupler that connects the front and rear case. It is important to match the dual adapter and rear gear set. If your rear case is going to run the stronger 23 spline gears you must also run a 23 dual adapter coupler. If your rear case is going to use 21 spline gears, then the dual adapter coupler must also be 21 spline.
In a dual transfer case with 21 spline gears in both cases the weak spot and most common failure point is the input gear to the rear case. A dual transfer case built with 21 spline gears in the front case and 23 spline gears in the rear case is stronger and now the most likely point of failure becomes the rear output shaft. If you‘re purchasing both a dual adapter and 4.70 gears for the rear case, order both in 23 spline. There is no cost difference building with 23 spline parts if you order both the dual adapter and gears in 23 spline configurations. To build a dual transfer case crawler, you will need most of the parts that make up high/low section of a gear-driven Toyota transfer case. Below is a photo showing the factory parts that you will need from a stock.
1. Weld the provided key stock to the side of the shift fork as shown above. This prevents the front transfer case shifter from going side to side and only allows it to shift front and rear.
1. Continued - If you have a forward shift transfer case, this is what your shift rail will look like with the key stock welded in place.
Please use only Trail-Gear provided or factory Toyota gaskets. You can easily identify the Toyota gaskets as they have green lines on one side. Some aftermarket gaskets do not have the proper oiling holes. Use of these gaskets in any dual adapter will result in failure, sometimes in as little as 5 miles. The result of this failure is that the bearing melts down and the drive train suddenly locks up after just a few miles of driving. This could easily cause an accident. Please don't use gaskets you have hanging around your shop or gaskets from other brand kits, unless you see the factory green stripes.
Transfer Case Oil:
After installing the transfer case, remove the rear fill plug and fill with 80/90W GL5 gear oil. Once oil starts leaking out of the fill hole, the transfer case is full. The transfer case oil level should be checked after 10 miles of driving and topped off as necessary. Conventional or synthetic oil may be used.
Transfer Case Oil Service Recommendations:
After any major internal work to the transfer case, we recommend that the oil be changed after the first 1,000 miles or after the first trail ride (which ever comes first) to remove debris suspended in the oil. After the initial change, the oil should be change once each year or each 10,000 miles which ever comes first. The fluid level in the case should also be checked each time the engine oil is changed. The fluid level should be checked after a roll-over as it is possible for fluid to leak out of the transfer case when the truck is on its side or is inverted.
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