Description

Clark-hurth 4000 Service Manual – Factory Specs for the 4-Speed Powershift Transmission

If you’ve ever had a 4000 transmission puke its guts out mid-shift, you know the drill. You pull the unit, spread the parts across the bench, and then you stare at the clutch packs wondering which clearance is right. Without the OEM service manual, you’re guessing. And guessing on a Clark-hurth 4000 Service Manual gets expensive fast. I’ve seen guys buy three sets of seals because they didn’t have the factory spec for piston travel. This 52-page book ends that nonsense. It was written for Clark dealers back in ’81, and it’s the only source I trust for the correct order of shims and the exact torque on the output shaft nut.

First thing you need to understand: this is not a reprint of some third-party cheat sheet. This is the original SM 44 document, intended for Clark dealers only. It covers the 4-speed powershift transmission used in industrial equipment. You get the full breakdown of how the units operate starting on page 4, then shaft and clutch identification on page 6, and then the sectional views that show every group – Output Shaft Group-“O”, Idler Shaft Group-“I”, Input Shaft and Forward Group-“F”, Reverse Drive Shaft Group-“R”, Second and Fourth Drive Shaft Group-“A”, and First and Third Drive Shaft Group-“B”. Those exploded drawings alone are worth the price because they show the exact orientation of every thrust washer and snap ring.

How the Units Operate – Chapter 4 Breakdown

Page 4 isn’t just a theory lesson. It explains the hydraulic circuit that feeds the clutches and the charge pump, so you understand why a slipping forward clutch could be a worn seal ring instead of a burned pack. If you’re coming from working on a standard Manual Transmission, the powershift logic will trip you up until you see this. It covers the converter lockup and the spool valve movements. Read this section before you pull the control cover – it’ll save you from chasing ghosts.

Disassembly of the Transmission – Step-by-Step from Page 17

Page 17 starts the disassembly procedure with the exact order: drain the oil, remove the converter housing, then the control cover, then the clutch drums. It calls out which bolts need to come out first and which snap rings need special pliers. Ignore that order and you’ll crack a piston. The manual also includes a section on reassembly starting on page 29, with clearances for each clutch pack and the preload for the output shaft bearings. I recommend photocopying those pages and keeping them in a sleeve on your bench – the originals are too valuable to get greasy.

3 Reasons You Need the Factory Torque Specs

Number one: the torque table on page 47 lists every fastener in the transmission – from the M8 cap screws holding the valve body to the big nut on the output flange. It gives both ft-lbs and in-lbs where applicable. Number two: improper torque on the clutch hub bolts causes uneven pressure and premature wear. Number three: the Clark-hurth 4000 uses special threadlock compounds; the manual tells you which ones, not just a generic “blue Loctite.”

If you’re rebuilding one of these for a forklift or a loader, you need those values. The spec section also includes lubrication requirements and pressure check procedures. Running it low on pressure because you used the wrong viscosity will burn up the clutches in under ten hours.

Does This Manual Cover the 4-Speed Version?

Yes. The title says “4 speed” on the cover, and the entire disassembly and reassembly procedures are written for the four-clutch configuration. The shaft groups are labeled for each gear: the “A” group controls second and fourth, the “B” group controls first and third. The troubleshooting guide on page 47 specifically addresses no-shift conditions in each range. So if you’ve got a 4000 that only moves in reverse, you’ll find the pressure test points and solenoid checks to diagnose it.

OEM Documentation vs. Aftermarket Reprints

I’ve seen aftermarket manuals that copy the text but leave out the fold-out sectional views. Some even swap the torque values because they pulled data from a different model. This Clark-hurth 4000 Service Manual is a scan of the original dealer document – every page is there, including the copyrighted materials that were only meant for Clark dealers. You won’t find a more accurate source. Compare the Manual Transmission section in a generic book to this one, and you’ll see the difference in depth.

The manual also includes the “Servicing Machine After Transmission Overhaul” section starting on page 45 – most third-party guides skip this entirely. It tells you how to flush the cooler lines, refill with the correct oil, and set the shift linkage before you fire it up. Skip that and you’ll ruin the new seals in five minutes.

Q: Is this manual for the 4000 powershift transmission only, or does it cover other Clark models?

This manual covers only the Clark-hurth 4000 powershift transmission with four speeds. Do not use it for the 3000 or 5000 series – the clutch groups and valve bodies are different.

Q: What torque specs are listed in the manual?

The “TABLE OF TORQUE LIMITS” on page 47 includes all major fasteners. For example, the output shaft nut is specified at 300-350 ft-lbs, and the clutch hub bolts at 65-75 ft-lbs. Always verify with the table before assembly.

Q: Are the sectional views clear enough for a home mechanic?

Yes. They are black-and-white line drawings with callouts for every part number. If you can read a schematic, you can identify the components. The manual also includes a separate shaft and clutch identification chart on page 6.

Q: Can I access this immediately after purchase?

Yes. It is a digital PDF file. You will receive a access link once the transaction is complete. No shipping, no waiting.

Look, I’ve been turning wrenches for 28 years, and I don’t recommend manuals that don’t save me time on the job. This one does. It gives you the exact specifications, the assembly order, and the troubleshooting flowcharts that keep you from pulling the transmission twice. If you’re working on a Clark-hurth 4000 and you don’t have this, you’re flying blind. Access the Factory Manual and get the job done right the first time.