2001 Toyota Tacoma Prerunner - Project Venture Toy

Most of the early Toy transfer cases used a 21-spline input gear shaft (left). When Toyota introduced the turbo engine models in 1986, they built the transfer case with a stronger 23-spline input (right). Inchworm provided us with a new Toyota 23 spline shaft to upgrade our front reduction box.

We actually found a crack in our donor case in the rear wall in the area where the two main bearings reside. This is not very common but can happen on occasion, especially if there has been some carnage within the transfer case.

We pre-lubed the bearings and installed the stock gears in the Advance case. We also transferred the stock case studs over to the new case.

As with any added Toy reduction case, we had to modify the high/low range shift rail by welding a supplied metal strap onto the rail end. This keeps the shifter captive in the rail since the adjacent 2WD/4WD rail is not used in the added reduction case. The shift fork and rail are installed followed by installation of the detent ball, spring and screw that serve to hold the shift rail in place in each of the shift positions.

Our next adapter was the Advance Adapters Dana 300/Atlas adapter. This 3.625-inch long adapter bolts to the rear of our Toyota reduction box and provides mating to our Atlas II. The kit includes a dual transfer case adapter plate, adapter housing, reduction housing output shaft, and the other hardware needed for the conversion.

We began this portion of the build by pressing the Toyota bearings into the new adapter plate. Advance supplies the caged needle bearing. The large ball bearings from our donor case were in good shape so we were able to reuse them for the conversion. Then the Atlas/Dana 300 adapter flange was bolted to the Toyota patterned plate.

With the Atlas adapter complete, it was bolted to the Toy reduction box. It uses the stock low gear from the reduction box combined with the new output shaft. We ended up using a high/low shifter rail from a forward shift Toyota case (not shown) to shift our 2.28:1 gearset. The shift rod exits through the top of the TH350-to-Toy transfer case adapter.

Our choice for the main transfer case was a 3.0:1 Atlas II. With its heavy 356-T6 aluminum case and all gear-driven design, this unit has proven itself to be a stout performer. The helical cut gears run quiet and low range options run from 2.0:1 to 6.0:1. The Atlas is built to your custom order and offers a number of configurable options.

The Atlas cases are available in both driver (shown) and passenger side drop to accommodate any vehicle. The input bolt pattern allows multiple clocking positions to setup the case at whatever angle you need to clear the body or provide maximum ground clearance. Ours came upgraded with the full 32-spline front output shaft and 1350 CV yokes.

Here's where the stuffing begins. To keep the transfer case from hanging too low we needed to cut the cab floor and rotate the Atlas upward. We ended up cutting a good sized hole in the floor under the driver seat to get the case in the position we wanted. We also had to relocate the steel fuel lines under the cab more to the driver side to clear the case.

Once we got a big enough hole sliced in the floor and the Atlas in place, we built a sheetmetal doghouse to cover the transfer case. This also led us to do some seat bracket fabrication as well to get our driver side Mastercraft seat mounted back in place.

Advance Adapters now offers a 1350 CV yoke that mates directly to the u-joint of a 1350 CV joint. The advantages of this yoke over the flange style yoke are cheaper cost and you gain a bit of driveshaft length due to the new yoke style.

It was time to build a custom crossmember for our new drivetrain. We've used thick flat bar in the past to build crossmembers and found it effective for building high clearance members and squeezing around obstacles such as the exhaust pipe. Without employing a body lift, we couldn't quite get the bottom of the transfer cases even with or above the bottom edge of the frame rail. They ended up a couple inches below. Our crossmember supports both the Toy reduction case and the bottom of the Atlas

Advance offers two ways to shift the Atlas: direct linkage or by cable shifter. We originally thought we would need to use the remote cable shift setup but were able to use the standard linkage setup and modify the shift rods such that they exit the floor near the right front corner of our driver seat. Here you see a bottom up view of the shifter going through the sheetmetal box we built into the floor.

Up top we had to make way for the Toyota case shifter. Of course, the 2WD Prerunner has no floor cutout for a t-case shifter so we sourced a 4WD version floor plate and rubber boot, which made for an easy bolt-on. We'll top it when done with a 4WD version plastic console. To the left are the Atlas shift rods and rubber boot.