Advance Adapters 50-3200 - Manual (Page 2)

GM TH400 AUTOMATIC TO NEW PROCESS
203/205 TRANSFER CASE 1971-79
ADVANCE ADAPTERS INC. P/N: 50-3200
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: 05-20-10
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
the transmission has been equipped with, and all of the new Advance Adapter output shafts will be interchangeable with your
transmission. The new shaft supplied with your kit should be installed by a competent mechanic. 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.
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 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.
On the side of the TH400 case, you will find a 1-15/16" hole that must be plugged with the soft plug provided in the kit. We
recommend that you use a good sealer when installing the soft plug in order to prevent any possible leakage.
The adapter plate bolts directly to the back of the TH400 transmission using 6 socket head cap screws that must be torqued to
25 ft/lbs. We do not recommend gasketing between the transmission case and adapter housing. We found it suitable to use a
blue silicone sealer for sealing. Make sure bolts do not bottom out in the TH400 case.
The vacuum modulator line will need to be shortened and re-routed to the right front side of the transmission. The original cooler
lines and fitting will line up with the TH400 transmission. The original flex plate and converter can be retained. The transmission
shift linkage can also be retained. The transmission dipstick must be from the TH400 application.
The 4WD linkage on a NP203 will remain mounted on the stock GM adapter housing. The NP205 handle can be relocated further
forward using bracket P/N715512. This bracket provides a new pivot location for the transfer case shifter handle. This bracket
bolts to the stock pivot hole on the GM casting and one of the holes to the governor gear cover.
The TH400 kickdown operates off an electric signal. We have found that Lokar's bracket works well. The part number for this
bracket is KD-2400 HT. Lokar's phone number is (423) 966-2269.
The original transmission crossmember will need to be relocated on the frame rails approximately 3-1/2" further back. The input
shaft on the transfer case has an "O"-ring seal that prevents transmission fluid from traveling through the splined coupler. Make
sure that the seal is undamaged and in the proper location.
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.