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Available from Advanced Adapters is the dual-case conversion kit that allows mating a second transfer-case reduction box to your stock transfer case to more than double your truck's low-range ratio. The kit adds about 651/48 inches in length to your drivetrain.

toyota transfer case rear cover

If you have seven bolts in the rear cover (as this case has), then you have a gear-drive transfer case. If you have five bolts in the rear cover, you have a chain-drive case.

Here is a side view of a stock transfer case combined with a dual-case conversion adapter and the additional stock reduction box. This setup requires shortening the rear driveshaft and lengthening the front driveshaft, an aid for the steep front driveshaft angle on a lifted truck.

Advanced Adapters has low-ratio gearsets for the gear-drive transfer cases. This kit replaces the standard 2.28:1 low-range reduction gears with a set that provides a 4.7:1 reduction.

In gear-drive transfer cases, most four-cylinder trucks use a 21-spline input gearshaft (left), but the beefier turbo cases use a stronger 23-spline shaft. Upgrading to the 23-spline unit (right) may be a wise choice for extreme-duty applications.

Available from Advanced Adapters is the dual-case conversion kit that allows mating a second transfer-case reduction box to your stock transfer case to more than double your truck's low-range ratio. The kit adds about 651/48 inches in length to your drivetrain.

Inchworm Rock Walkin' Gear sells its dual-transfer-case adapter that is machined from billet 6061 T6 aluminum. Included in their conversion kit is a modified factory output shaft that accepts all factory bearings and related parts.

Inchworm Rock Walkin' Gear sells its dual-transfer-case adapter that is machined from billet 6061 T6 aluminum. Included in their conversion kit is a modified factory output shaft that accepts all factory bearings and related parts.

The Twin Stick Conversion Kit from Front Range Off-Road Fabrication adds a second shift lever to your transfer case and allows you to independently control high/low range and two-wheel-drive/four-wheel-drive functions.

Marlin Crawler's latest dual-case conversion kit is the MC07. This design uses a double roller bearing and oversized billet output coupler shaft. This model has proven to be quieter, stronger, and yet more reliable than any previous model. Oil circulation and cooling efficiency have been improved as well.

The stock transfer case crossmember is bulky and hangs low. Building your own replacement or installing a trick unit like this one from BudBuilt can buy you a cool 2 inches of extra clearance under your vehicle's belly. These crossmembers include a large skidplate and are available with a built-in drivetrain lift, if desired.

All Pro Off Road sells this heavy-duty output shaft made from 8620 billet steel, hardened to 58-60 Rockwell hardness. The stock weak points have been reinforced to improve overall strength. When the input shaft is upgraded to 23 splines, the weak point in the transfer case then becomes the output shaft. This new shaft addresses that issue.

A unique approach to overcoming the bulky stock crossmember is this crossmember/skidplate combo from Front Range Off Road Fabrication. It requires minor welding for installation but offers clearance gains of up to 3 inches, plus firmer mounting of the entire drivetrain to reduce the habitual tearing of stock motor mounts under extreme use.

You can't beef up your Toyota drivetrain and neglect the driveshafts. The stock shafts or standard aftermarket ones use thin-wall tubing as shown in the upper cross-sections here. Rockstomper builds beefy replacements that have smaller tubing using heavy 0.25-inch-wall tubing (lower piece). The scarred shaft in this picture is a Rockstomper shaft that has been severely abused but is still running strong.

If you're looking for a better parking brake or trying to supplement a rear disc-brake conversion without parking brake, consider this complete kit offered by All Pro Off Road. It mates cleanly to the rear of the transfer case and mates with the stock cable assembly. Braking power at the transfer case flange is multiplied at the ground by your rear axle ratio.

When swapping driveshafts on Toyota transfer cases and third members, the driveshaft flange bolt patterns sometimes vary. A simple trick to allow swapping among the various patterns is to drill a second bolt circle offset 45 degrees from the original one. All Pro also sells a new replacement flange that is pre-drilled with two patterns.