Spicer Single Drive Axles Service Manual: 34DS, 34RS, 38DS, 38RS, DS340, RS340, DS380, RS380, DS400, RS400, DS3 - Manual (Page 70)

Inter-Axle Differential Lockout Overhaul.
67
"Reverse-Air" Lockout Overhaul
The "reverse-air" lockout unit is spring-operated to engage lockout and air-operated to disengage lockout. A clutch engages or
disengages the helical-side gear to lock or unlock the inter-axle differential.
Service Parts Availability
A new design of the original "Reverse-Air" Lockout has not been released at this writing. The piston, body and cover of the original
lockout are no longer available as individual parts. If these parts are not serviceable, replace the complete unit. For other parts,
use a Service Parts Kit (see illustration for contents). For additional information, refer to Dana Parts Books (see back cover).
Procedure - Disassemble Lockout.
1. Remove cap screws and lock washers fastening cover to
body. Remove cover, "O" ring and compression spring.
2. Remove push rod nut and flat washer.
3. Remove body cap screws and lock washers. Then remove
body, body "O" ring, and piston as an assembly. Remove seal
ring from threaded end of push rod.
Shift fork
and push rod
Lockwasher
Lockwasher
Capscrew
Capscrew
Push rod
seal ring
Body
O-ring
Cover
O-ring
Lockout
body*
Felt
oilers
Flat
washer
Nut
Piston
O-ring
Piston*
Cover*
Compression
spring
"Reverse-Air" Lockout
*Non-serviceable parts