4L60E to NP205 Transfer Case Adapter Kit
This adapter kit was originally used on 1971–1979 GM 4WD trucks equipped with a TH350 automatic transmission and the NP205 cast-iron, part-time transfer case. It allows a newer GM 4L60E transmission to bolt directly to the NP205 transfer case, making it an ideal solution for drivetrain upgrades and transmission swaps.
Designed for builders looking to combine the strength of the NP205 with the improved performance and electronic control of the 4L60E, this kit ensures proper alignment, reliable power transfer, and OEM-quality fitment between the 4L60E transmission and transfer case.
4L60E Transmission Compatibility
In 1996, GM introduced an updated version of the electronically controlled 4L60E transmission featuring a removable bellhousing and a 21.5-inch overall length. This version uses a hex-style output bolt pattern, similar to the TH400, making it compatible with this adapter design.
The 51-0405 adapter was engineered to make this style of 4L60E function like a 700R4, allowing seamless integration with the NP205 transfer case. This design enables proper speed signal generation for electronic drivetrain control modules while maintaining durability under load.
Integrated Speed Sensor & Reluctor System
This adapter kit includes a clamp-on reluctor ring and speed sensor that generates a 40-pulse-per-revolution output signal, ensuring accurate speed input to the vehicle’s drivetrain or engine control module. The reluctor ring installs over the stock governor gear on the included 700R4-style output shaft.
Two sensor mounting locations are provided on the adapter to allow flexible installation. The unused sensor port is sealed using the included plug.
Heavy-Duty Output Shaft Construction
The included one-piece GM 700R4 output shaft is manufactured from 4340 alloy steel and meets or exceeds OEM material and quality standards. This shaft is designed to handle the torque demands of off-road use, towing, and heavy-duty applications.
This mainshaft kit is compatible with 4L60, 4L60E, and 700R4 overdrive automatic transmissions, providing flexibility across multiple GM drivetrain configurations.
What’s Included (Bill of Materials)
- Adapter: 4L60E to NP205 (51-5302A)
- Adapter: 4L60E/700R4 Universal (51-0405)
- Output Shaft: 700R4 to NP203/205 (52-6900)
- Coupler: GM 27-spline transmission to 27-spline transfer case (52-9503B)
- Reluctor Ring: 700R4 Integral Clamp (716072)
- Speedometer Sensor (300619)
- Reluctor Sensor Plug – 22mm (716079)
- GM Nylon Bushing (716082)
- GM Transmission O-Ring (716511)
- NP205 Adapter Gasket (716572)
- NP205 Seal (716745)
- Hardware:
- 10mm x 1.5 x 40mm SHCS (720046)
- 10mm x 1.5 x 45mm SHCS (720074)
Ideal For
- 4L60E transmission to NP205 transfer case swaps
- GM drivetrain conversions and restorations
- Off-road, towing, and heavy-duty 4WD builds
- Replacing TH350 setups with modern overdrive transmissions
This adapter kit provides a complete, durable solution for mating a 4L60E transmission transfer case combination while preserving the strength and reliability of the NP205.
Bill Of Materials
