Muncie GA6B and GM6B PTO parts

What the GA6B and GM6B are

Both are clutch shift PTOs: a clutch pack of six friction discs and five stators, engaged by a piston from transmission pressure through a 12 volt solenoid valve. They bolt to the 6-bolt opening on the Allison 1000 and 2000 series automatic transmissions.

The parts list covers both on one set of internal parts. The GA6B is the standard clutch shift unit with its activation kit. The GM6B is the PTO unit only: the mounting kit, activation kit and heat shield kit are sold separately.

Where it fits

Muncie's parts list is written for the Allison 1000 and 2000 series. The GM6B installation instructions (IN01-03) cover the GM 3600 cab chassis with the Allison 1000, and tell you to contact Muncie for other GM chassis with Allison automatics. For GM model years 2001 to 2006 the parts list calls for installation kit 48TK4415, and for model year 2007 and later it lists tubing and heat shield kit 48TK4962.

Muncie's owner's manual says a clutch shift PTO on an Allison 1000 or 2000 must be wired to the transmission's PTO enable circuit (terminal J106 on the WTEC II, pin 43 on the Gen IV), which allows full PTO output. The GM6B comes with wiring that already controls that circuit.

Reading a GA6B or GM6B model number

The order is PTO type, mounting, transmission gear, speed ratio, shift type, assembly arrangement, output, special feature. Muncie's example is GA6B-A68 05-H1TX:

• GA is the clutch shift unit with activation kit and GM is the unit without it.
• 6B is the 6-bolt standard metric mounting.
• A68 is the Allison 6.86P 20 degree spur gear.
• 05 is the 0.47:1 speed ratio.
• H is the 12 volt electric/hydraulic shift.
• 1 is the assembly arrangement.
• T is the SAE "A" 2-bolt output, and X means no special feature.

The parts list is headed GA6B-A6805-H1TX and GM6B-A6805-H1TX, so those are the two complete model numbers it covers.

Parts that wear and what to order

• Clutch discs and stators, piston and O-rings from the Service Parts List and Description section, when the PTO slips or drags.
• Input bearings and shims. The input gear runs on tapered bearings set with one of eight shims; the book gives the preload as 0.002 to 0.006 inch loose.
• GA6B kits 48TK4211 and 48TK4212 with the switch, solenoid valve, pressure switch, fittings and wiring.
• GM6B kits 48TK4415, 48TK4962 and 48TK4963, which add tubing, brackets, shield and harness.
• Solenoid valve 35T37928, with replacement cartridge 35T36092, and the stud kit 20TK4058, plus the two mounting gaskets.

Questions we get about the GA6B and GM6B

Do I need a GA6B or a GM6B?

The GM6B is the PTO-only unit, and its installation sheet covers the GM 3600 cab chassis with the Allison 1000. The GA6B is the version supplied with its activation kit. Send us the chassis, year and transmission and we will help sort it.

How many mounting gaskets does it take?

Muncie's manual says to install the GA6B or GM6B using both 13M13541 gaskets provided. If it is noisy afterward, see PTO troubleshooting.

Where do I find installation steps?

The GM6B instructions are IN01-03, used with the PTO owner's manual IN84-03, and both are listed under the PDF manuals for this series.

GA6B / GM6B parts breakdown

How the Muncie GA6B and GM6B PTO parts list is organised on our store. Each section opens the exploded view with every part number, the quantity used and an order button.

Muncie GA6B & GM6B Series

GA6B / GM6B manuals

All GA6B / GM6B books: Muncie PTO parts manuals.

Need a complete rebuilt unit?

Our sister site rebuiltmunciepto.com covers rebuilt GA6B / GM6B units. This site is the parts and model reference side.