Advance Adapters 50-6801 - Manual (Page 2)

GM TH350 AUTOMATIC TO JEEP NP207
T/C (21-SPL) upgrading to a 23-SPL
ADVANCE ADAPTERS INC. P/N: 50-6801
P.O. Box 247, 4320 Aerotech Center Way Old Part No: 711068-21
Paso Robles, CA 93447 PAGE 2 OF 3
Telephone: (800) 350-2223 Fax: (805) 238-4201 Page Rev. Date: 03-27-13
SPECIAL NOTE: The components packaged in this kit have been assembled and machined for specific type of conversions. Modifications to any of the components will
void any possible warranty or return privileges. If you do not fully understand 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 values, wiring diagrams and other related equipment. These manuals are normally available at automotive
dealerships and parts stores.
GM TH350 3 SPEED AUTOMATIC
The General Motors TH350 has a case length of 21-1/2", 13 bolts for holding your oil pan in position and is available in
two different engine to transmission bolt patterns. The case is available with a Chevy bolt pattern that has the top two holes
8-1/4" apart or in a Buick bolt pattern that has the top two holes 7" apart. The rear side of the transmission case should
have a square bolt pattern that uses 4 bolts. There are several various lengths of output shafts that these transmissions
have been furnished with and you will be required to disassemble your transmission for use with the new shaft provided.
The new shaft will have 21 splines that will engage directly into your transfer case. The speedometer gear is normally
located in the tailhousing, but when adapting it to the transfer case, the location will change to the back side of the transfer
case. The rear transmission support is located in the main case just forward of the tailhousing connection. This can be
used for supporting the crossmember on some installations, but most of our kits provide support on the new adapter
housing.
Install the new 23 spline NP207 input gear into the New Process 207 transfer case. A new pocket bearing has been installed
and you will need to refer to a service manual for the installation of this input gear.
When installing the new transfer case adapter, make sure that the input gear and the output shaft do not bottom out. We
have found on occasion that a transmission output shaft may be slightly longer than we have allowed for. The adapter
housing and transmission output shaft must be assembled to the back of the transmission without interfere.
DO NOT
FORCE THE NEW TAILHOUSING ONTO THE TRANSMISSION. If assistance is needed, please feel free to call the
number listed above.
When assembling the adapter housing to the transmission case, we have provided you with a new square-type "O" ring
seal to prevent fluid leakage. This seal is a stock GM item that is used on all TH350 installations.
If you have selected a transmission that has the old style modulator, then we recommend the use of the Advance Adapters
adjustable modulator Part No. 716010. This will also allow for additional driveshaft clearance.
All installations will require the use of a transmission cooler. The cooler can be either installed in the radiator or a remote
location is acceptable. The transmission shift control can either be a Hurst floor mounted type shifter or sometimes the
existing column shift can be modified on certain applications.
The adapter crossmember support is designed around replacement of a manual transmission. If you are replacing an
automatic transmission, you will find that the crossmember support will hang too far down when it is bolted to the bottom
of our new adapter housing. We suggest that you purchase a crossmember support from the manual transmission
application to simplify this problem.
Two rotations are provided on the casting. Choose the rotation that best suits your application. Two of the positions on the rotation
will require removal of two studs from the transfer case and substitution by the two 3/8"-16 x 1-1/4" Socket Head Cap Screws. This
is due to lack of wrench clearance around the casting. Use silicone sealant on both sides of the transfer case gasket. Use Loctite
on all bolts.
CAUTION: This adapter kit is not compatible with the Jeep vehicles 1980-86 that are equipped with the Dana
300 transfer case. Do not attempt to use this adapter without major modifications.