WOD TH400 to Atlas Transfer Case Top Mount Adapter (Replaces Advance Adapters)
WA05050
The TH400 to Atlas Transfer Case Top Mount Adapter is engineered for builders who need maximum drivetrain protection, improved undercarriage clearance, and cleaner packaging in extreme off-road applications. Manufactured by Wide Open Design, this adapter allows the drivetrain to be supported from above rather than relying on a traditional bottom-supported configuration that leaves the transmission and transfer case exposed to rocks, ledges, and hard trail impacts.
Machined in-house from 6061 aluminum, the adapter is designed for GM TH400 4WD transmissions with 1.375" of output shaft stickout and directly replaces Advance Adapters part number AS-6401. Its top-mount design helps keep the drivetrain higher in the chassis while creating additional room for exhaust routing, skid plate design, crossmembers, and surrounding suspension components.
Includes:
- (1) Wide Open Design TH400 to Atlas Top Mount Adapter
- Atlas Transfer Case Mounting Hardware
- Direct Replacement Configuration for Advance Adapters AS-6401
Specifications
| Specification | Details |
|---|---|
| Manufacturer | Wide Open Design |
| Product Type | Transmission-to-Transfer Case Adapter |
| Transmission Compatibility | GM TH400 4WD |
| Transfer Case Compatibility | Advance Adapters Atlas Applications |
| Output Shaft Stickout | 1.375" |
| Replacement Part Number | Advance Adapters AS-6401 |
| Material | 6061 Aluminum |
| Mounting Configuration | Top-Mount Drivetrain Support |
| Manufacturing | Machined In-House in the USA |
| Primary Benefit | Improved Drivetrain Protection and Undercarriage Clearance |
Fitment
| Component | Compatibility |
|---|---|
| Transmission | GM TH400 4WD |
| Transmission Output Shaft | 1.375" Stickout from Transmission Case |
| Transfer Case | Advance Adapters Atlas Applications Using AS-6401-Style Configuration |
| Vehicle Application | Universal Custom Off-Road Chassis |
Fitment Notes
- Designed for GM TH400 4WD transmission applications.
- Requires exactly 1.375" of transmission output shaft stickout measured from the transmission case.
- Designed for Atlas transfer case installations that use an Advance Adapters AS-6401-style adapter configuration.
- Suitable for rock bouncers, Ultra4 cars, rock crawlers, trail rigs, and custom tube chassis.
- Provides additional packaging room for skid plates, exhaust systems, crossmembers, and surrounding chassis components.
- Verify transmission output shaft length and Atlas transfer case compatibility before installation.
FAQ
1. Why use a top-mount adapter instead of a bottom-supported design?
A top-mount adapter allows the drivetrain to be supported from above, helping keep the transmission and transfer case tucked higher into the chassis. This reduces exposure to rocks, ledges, and direct trail impacts underneath the vehicle.
2. How does this adapter improve undercarriage clearance?
By removing lower-mounted support structure from beneath the drivetrain, the adapter creates more usable space for a flatter skid plate and a cleaner belly profile. This can improve breakover clearance in rock crawling and technical trail conditions.
3. Why is the 1.375-inch output shaft measurement important?
The adapter is machined around a specific TH400 output shaft stickout. An incorrect shaft length can prevent proper transfer case engagement, alter internal spline contact, or create assembly interference, so the measurement must be confirmed before installation.
4. What advantage does 6061 aluminum provide?
6061 aluminum offers a strong balance of structural rigidity, machinability, corrosion resistance, and reduced weight. Precision machining also allows the transmission and transfer case mounting surfaces to remain accurately aligned.
5. What should be checked during installation?
Verify output shaft stickout, spline engagement, adapter and transfer case alignment, mounting hardware clearance, driveline angle, exhaust routing, and skid plate placement before final assembly. The top support structure must also be integrated into the chassis strongly enough to carry drivetrain loads.
