Muncie CS20 and CS21 PTO parts
The CS20 and CS21 are Muncie's compact clutch shift PTOs for the Allison 3000 and 4000. This page explains the parts list, the model number and the solenoid choices before you order.
Send a photo of your PTO tag and we will confirm the model.
CS20 / CS21 at a glance
- Type
- Clutch shift PTO, 10-bolt mounting, electric over hydraulic shift
- Fits
- Allison 3000 and 4000 series (transmission code A10)
- Speed ratios
- Seven codes, 05 (.55:1) to 15 (1.47:1)
- Torque rating
- 200 to 325 lb ft intermittent, depending on ratio
- Shift voltage
- 12 volt (code H) or 24 volt (code J)
- CS21 difference
- Remote mounted solenoid valve
- Main parts book
- SP96-01 CS20/CS21 Series Service Parts Manual
What the CS20 and CS21 are
The CS20 is a clutch shift PTO built on the same technology as the larger CS10 but about 20 percent smaller. A clutch pack inside engages the output when the cab switch opens a solenoid valve and sends transmission oil pressure to the clutch piston. Muncie's integrated drag brake helps stop the output shaft once the PTO is switched off.
The CS21 is the same PTO with the solenoid valve mounted remotely, which makes it more compact. Both come in two housing configurations, so the shaft can sit high or low on either side of the transmission, and the pump flanges rotate 360 degrees.
Where it fits
The CS20 mounts on the 10-bolt opening of Allison 3000 and 4000 series transmissions; the model number code is A10. Muncie's shaft extension chart lists CS20 kits for both, but none for the 7 speed HD4070 or for 4000 units with a retarder or rear mounted oil cooler, and a rear transmission support is required. See PTO shaft extensions and EX Drive.
Muncie names these jobs for the CS20: snow and ice control, tandem and triple axle dumps, fuel haulers, refuse trucks, digger derricks and aerial devices.
Reading a CS20 model number
A tag reads: series, transmission and ratio, shifter, assembly arrangement, output type, special feature. Muncie's example is CS20-A10 08-H 1 C X: a CS20 for Allison, ratio 08 (.84:1), 12 volt electric over hydraulic shifter, arrangement 1, 1410 companion flange output, no special feature. In the mounting digits, 10 and 20 have the solenoid on the PTO; 11, 21 and 41 have a remote shift solenoid valve.
- Ratio: 05 .55:1, 06 .64:1, 07 .74:1, 08 .84:1, 10 .97:1, 12 1.19:1, 15 1.47:1.
- Arrangement: 1 or 3; Muncie's extension chart treats 1 as right side and 3 as left side, shaft low.
- Output: B 1 1/4 inch round, C 1410 companion flange, 2 DIN 100 companion flange, I DIN 5462, K SAE B 2 and 4 bolt, S SAE B 2 bolt, P SAE BB 2 and 4 bolt, Q SAE A 2 bolt, Z SAE B flange with SAE C shaft.
- Special feature: X none, B 48 inch hose kit, 3 17 inch lube hose kit, 4 lube hose delete, U pulse generator.
The model number guide covers all series.
Parts that wear and what to order
- Input gear assembly (Table A): sold only as an assembly, because the cone spacer that sets bearing preload at .002 to .006 inch loose comes with it.
- Clutch parts: friction and spacer discs, piston, piston cup, and the bell gear by ratio (Table D). The CS20-RBK rebuild kit bundles them with bearings and seals.
- Output shaft and cover (Tables E and F): one shaft and one flange per output code.
- Solenoid valve: the drop-in valve is the type for January 2008 and later; units before 2008 use a screw-in Hydroforce or Delta valve. The CS11/CS21 block type valve has its own section.
- Kits: installation kit 48TK5017 (12 volt), CS21 conversion kit 48TK5076, gasket kit CS20-GSK, and hose kit 43TK4036 for the CS21.
Questions we get about the CS20 and CS21
Which solenoid does my CS20 use?
It depends on the build date. Muncie's list splits at January 2008: drop-in valve from then on, screw-in valve before. The rear cover differs too, so confirm the date.
My CS20 will not engage or has weak torque. What does Muncie check?
Engage at idle, under 1,200 rpm at the output shaft, with 400 psi gauges at the PTO inlet and the pressure switch port. Under 150 psi, check the hoses and the transmission port; over 50 psi difference between gauges points to the solenoid and orifice. See PTO troubleshooting.
The output shaft spins with the PTO off. Is that normal?
Clutch packs can drag in cold oil, so warm the transmission first. If it persists after installation, Muncie says to check the wiring, then the drag brake adjustment.
CS20 / CS21 parts breakdown
How the Muncie CS20 and CS21 Clutch Shift 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 CS20 & CS21 Series
CS20 / CS21 manuals
All CS20 / CS21 books: Muncie PTO parts manuals.
Need a complete rebuilt unit?
Our sister site rebuiltmunciepto.com covers rebuilt CS20 / CS21 units. This site is the parts and model reference side.
Get a quote on CS20 / CS21 parts
Send the model number off the PTO tag, a part or item number, or simply what the PTO is bolted to. A parts specialist answers during business hours.