Advance Adapters 50-6306 - Manual (Page 2)

GM 4WD TH350 AUTOMATIC TO JEEP NP231 T/C
21 SPL. upgrading to a 87-95 23 SPL.
ADVANCE ADAPTERS INC. P/N: 50-6306
P.O. Box 247, 4320 Aerotech Center Way Old Part No:
Paso Robles, CA 93447 PAGE 2 OF 5
Telephone: (800) 350-2223 Fax: (805) 238-4201 Page Rev. Date: 04-10-13
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 holding the 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 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 must make sure the proper shaft has been installed into the transmission for use with the
Advance Adapter transfer case kit. We standardize our kits on the GM 4 wheel drive output shafts that were used in vehicles
1973-79. If the transmission you purchased had the correct output shaft, you can return the new output shaft for credit.
All TH350 output shafts will have 27 splines. 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 the Advance Adapter kits provide support on the new adapter housing.
When installing the new transfer case adapter, make sure that the coupler 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; and when coupling
into our new spud shaft, we find a small amount of interference. The adapter housing and spud shaft must be assembled
to the back of the transmission without interference.
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. Use silicone sealant on
both surfaces of the transfer case gasket and Loctite all fasteners.
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.
INSTALLATION:
1. This kit comes pre-assembled with the bearing, snap rings, and spud shaft installed in the casting. The bearing and spud
shaft are a press fit. The spud shaft is pressed to the bearing and the snap ring installed to retain the spud shaft properly.
The bearing and spud shaft assembly are also a press fit into the adapter housing. The bearing and spud shaft are pressed
into the casting. This assembly is retained with the provided snap ring.
2. Install the o-ring on the casting and use a small amount of silicone to provide a good seal. Bolt the adapter assembly
to the TH350 transmission.
3. Using a thin film of silicone on both sides of the transfer case gasket, install the transfer case and gasket to the adapter
assembly. The studs in the NP231 should locate the transfer case in the proper rotation.
4. The Advance Adapters crossmember mount will bolt to the bottom of the adapter casting. Mark and drill new holes
in the skid plate to secure the transmission assembly to the skid plate.
5. Make sure all fasteners are secured and Loctite is used.