Advance Adapters 50-3202 - Manual (Page 2)

GM 2WD 32T TH400 AUTOMATIC TO
NP205 TRANSFER CASE 1971-1984/85
ADVANCE ADAPTERS INC. P/N: 50-3202
P.O. Box 247, 4320 Aerotech Center Way Old Part No: 711032
Paso Robles, CA 93447 PAGE 2 OF 3
Telephone: (800) 350-2223 Fax: (805) 238-4201 Page Rev. Date: 07-14-10
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 TURBO 400 3 SPEED AUTOMATIC
The GM TH400 has a case length of 24-3/4", 13 bolts for holding the oil pan in position, and is available in 3 different engine
to transmission bolt patterns. Make sure you have selected the proper TH400 for your particular engine. The rear side
of the transmission case will have a hex shaped bolt pattern that uses 6 bolts. There are several various lengths of output
shafts that these transmissions have been equipped with, and you will need the standard 2WD output shaft that protrudes
4-1/2" beyond the main case. The speedometer gear is normally located in the tailhousing but when adapting it to the transfer
case the location will change to the backside of the transfer case. The rear transmission support will now be located on
the new adapter housing or, in some cases, on the transfer case.
This adapter kit includes a new input gear and bearing for the NP205 transfer case. This gear has a 32T internal spline
that requires a larger bearing than most Chevy NP205 transfer cases. This gear is a stock GM item that was used on one
ton vehicles only. The transfer case must be completely disassembled and the case machined to accommodate the new
bearing furnished. Be sure to inspect the seal area provided in the adapter housing to make sure that it has the proper contact
on the new sleeve and gear supplied.
This transfer case will require some machining to accept the larger bearing. We have provided a new gasket to be installed
between the adapter plate and the transfer case to allow proper load heights on the bearing. This gasket is a stock GM
component, and it will require some trimming to fit over the new larger bearing.
When installing the new transfer case adapter, make sure the new 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; and when coupling
into out 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.
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 vacuum modulator line will need to be shortened and rerouted to the right front side of the transmission. The original
cooler lines and fitting will line up with the TH400 transmission. The original flexplate and converter can be retained. The
transmission shift linkage can also be retained. The transmission dipstick must be from the TH400 application.
The TH400 kickdown operates off an electric signal. You will be required to purchase a late model gas pedal bracket, GM
No. 1242101 and switch, GM No. 39772676.
The original transmission crossmember will need to be relocated on the frame rails due to the new transmission length.