Advance Adapters 50-2400 User Manual

ADVANCE ADAPTERS INC. P/N: 50-2400

P.O. Box 247, 4320 Aerotech Center Way Old Part No: 711024
Paso Robles, CA 93447 PAGE 1 OF 2
Telephone: [phone] Fax: [phone] Page Rev. Date: 06-22-12

GM TRUCK 4 SP MODEL SM420 TO

JEEP & SCOUT DANA 18/20

KIT CONSISTS OF:

No. Qty Part No. Description

1. 1 51-1200 CASTING (Ref: 711112)

2. 1 52-2400 OUTPUT SHAFT (Ref: 711324)

3. 1 716224 MOUNT BLOCK

4. 2 716453 SNAP RING

5. 1 716508 GASKET (GM #384-9472)

6. 1 716568 GASKET

7. 8 723722 H.H.B. 3/8"-16 x 1-1/4" LG.

8. 2 723723 H.H.C.S. 3/8"- 16 x 1-1/2"

9. 2 724342 F.H.S.C.S. 7/16"-14 x 2-1/2"

10. 2 724351 7/16"-14 x 1/2" SET SCREW

11. 1 728701 NYLON LOCK NUT

12. 1 JP001 JEEP INSTRUCTION MANUAL

GM & CHEVY SM420 TRUCK 4 SPEED 1948-1967

This transmission can be identified by a cast iron case length of 10-1/2". The casting numbers on the side of the case
should be GM3761930 or GM3813389. The transmission has a shift cover that bolts over the top of the transmission
that has a shift cover part number of GM591568. The P.T.O. opening is on the left hand side of the main case and the
transmission has a non-synchro first gear.

The adapter kit consists of a new main shaft that will need to be installed into your transmission. This should be done
by a competent mechanic. The SM420 transmissions have had three different styles of main shafts. From 1948 to 1949,
the shafts had a 10 tooth output, but used a 22 spline first gear. When using adapters that require a new main shaft, you
will be required to purchase a new first gear compatible with our main shaft. Transmissions 1948-67, all use the same
output shaft which will be interchangeable with our new main shaft.

OPTIONAL ITEMS:

Qty Part No. Description

1 716003 CROSSMEMBER MT.
1 716302 SEALED BEARING
1 716001 or 716002 T90-T86 BRG. RET.
1 716009 FRONT YOKE

The right side of the main case will need to be ground off for clearance of the front output yoke on certain installations.
For early Jeeps with the Dana 18 and the larger yoke, we do offer a smaller front T/C yoke kit 716009. We recommend
a trial fit with your transfer case and front output yoke so that any modifications that may be required can be done before
final installation into the vehicle. This is also a good time to set up the shifter linkage for the transfer case controls.

The early Chevy truck 4 speeds were equipped with the small front bearing retainer that is 4.686" in diameter and must
be used with either early truck bellhousings or late model car type bellhousings. The late model truck bellhousings all use
a 5-1/8" retainer size that will not be compatible with this transmission.

This adapter housing has two holes that will need to be plugged with the two set screws provided. Thread Lock or RTV
blue silicone is recommended when installing the set screws to prevent leakage. These castings are designed for Toyota
Land Cruisers and Jeep applications. You will only plug the holes on Jeep applications.

NOTE: We have seen a couple of SM420 transmissions that were equipped with a 32 spline output shaft.

Transmissions having this 32 spline output shaft used a special narrow 307 bearing. When using this kit with
the 32 spline shaft, you will be required to obtain a new rear output bearing BCA #307-L.

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.

ADVANCE ADAPTERS INC. P/N: 50-2400

P.O. Box 247, 4320 Aerotech Center Way Old Part No: 711024
Paso Robles, CA 93447 PAGE 2 OF 2
Telephone: [phone] Fax: [phone] Page Rev. Date: 12-16-99

GM TRUCK 4 SP MODEL SM420 TO

JEEP & SCOUT DANA 18/20

DVANCE

DAPTERS

51-1200

NOTE:

On Jeep applications, these two holes must be
plugged with the two set screws provided to
prevent leakage. Using RTV blue silicone or
thread lock is recommended.

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.