Advance Adapters 50-0431 - Manual (Page 5)

NOTES:
1. Be sure that the adapter shaft and T/C input gear do not bottom out prior to the adapter meeting flush with the
transmission. Some models may require the output shaft to be shortened.
2. The adapter has provisions for a new seal (NAT #456057). The outside diameter is 3.75" and the inside diameter is
1.937". The seal must be installed with the open side towards the transmission.
Once the input gear is removed, you'll find a thrust washer that must be reinstalled onto the
new 23 spline input. When comparing the two input gears, they should look the same except
for the internal splines. If you find a difference between the two. The NP231 transfer case
used two styles of front input bearings. The early transfer case used a wide bearing and
the later model used a narrow bearing. This new input gear is designed for only the early
style case. New Process changed the bearing and gear pitch design in 1995. The center
photo below show a later model input compared to a early.
Once you have verified that you have the same style input gear, install the gear into the planetary, install the snap ring. Re-install the planetary
assembly into the case and secure the input to the bearing with the front snap ring. Note: The only part you should have left out of the case
is the old input gear. During reassembly, make sure the oil return hole matches the front retainer hole.
NOTE: This kit will not work
with a Tera low 4:1 NP231 kit.
SPECIAL NOTE: The components packaged in this kit have been assembled and machined for specific types of conversions. Modifications to any of
the components will void any possible warranty or return privileges. If you do not fully understand the modifications or changes that will be required to
complete your conversion, we strongly recommend that you contact our sales department for more information. This Instruction Sheet is only to be used
for the assembly of Advance Adapter components. We recommend that a service manual pertaining to your vehicle be obtained for specific torque vales,
wiring diagrams and other related equipment. These manuals are normally available at automotive dealerships and parts stores.
ADVANCE ADAPTERS, INC. P/N: 50-0431
P.O. Box 247, 4320 Aerotech Center Way New Kit: (02/03)
Paso Robles, CA 93447 PAGE: 5 OF 5
Telephone: (800) 350-2223 Fax: (805) 238-4201 Page Rev. Date: 02-11-13
GM 4L60E TO NP231 TRANSFER CASES (21SPL)
upgrading to 87-95 23SPL.