Description

Rexroth Bosch A6VM NG 28 Repair Manual

I’ve been wrenching on hydraulic motors for twenty-eight years, and I can tell you right now: the difference between a rebuild that lasts and one that pukes oil on the shop floor is the spec sheet you’re holding. This Rexroth Bosch A6VM NG 28 Repair Manual is what the factory techs pull off the shelf when a variable displacement motor comes in for a major. It’s not a reprint, not a third-party summary, not some scanned copy with coffee rings. It’s the actual OEM document Bosch Rexroth sends out when you order a repair manual for the A6VM NG 28, series 63. Thirty-two pages, double-sided, and every torque value comes straight from the German engineering team that designed the motor.

What This 32-Page Repair Manual Covers

You’re getting the same content you’d get if you bought the paper copy from the factory a decade ago. The table of contents is short and purposeful: product description, exchanging external subassemblies, and checking/adjustment. No filler. The manual starts with a safety chapter that tells you exactly how to avoid hydraulic injection injuries and what happens if you ignore the pressure-relief steps. Then it walks you through identifying your specific A6VM variant using the type code on page 11. After that, page 15 kicks off the subassembly exchange section—this is where you find the step-by-step procedures for swapping the control unit, the swashplate, and the barrel assembly. Each step lists the required tools, the order of disassembly, and the critical torques you must hit.

Why OEM Documentation Beats Aftermarket Copies

I’ve had three aftermarket manuals land on my bench that claimed to cover the A6VM NG 28. Two of them listed the wrong drain-port torque and one skipped the preload procedure entirely. That kind of crap gets your customer a blown seal a week after the job. OEM documentation from Bosch Rexroth means the values have been verified by the engineers who designed the motor. The manual includes the exact tightening sequence for the valve plate bolts, the correct shim thickness for the control piston, and the test pressures for the high-pressure relief valves. You don’t have to guess if 30 ft-lb is right—it’s printed on page 16. And if you need to match the pump you’re working on with a compatible Rexroth A2FM/E Series 61 Repair Instructions for a different project, you can cross-reference the same factory logic.

Start with the External Subassemblies on Page 15

When a motor comes in with a case drain leak or a sticking control, you don’t tear down the whole unit. The manual walks you through exchanging external subassemblies without splitting the main housing. That saves real time. On page 15 you’ll find the procedure for swapping the LS (load sensing) port block, the flushing valve, and the speed sensor. Every step tells you which O-ring size to use and whether you need a backup ring. Before you start, read the safety warnings on page 7—the manual is blunt about trapped oil pressure and what happens if you crack a line without relieving it. After you’ve replaced the subassembly, you go to the checking section on page 25 to verify the settings.

Check Your Work Using the Factory Specs on Page 25

This is where most rebuilds go south. You replace a part, button it up, and then you have no idea if the displacement limiter is set right. The checking chapter on page 25 gives you the test bench procedure and the on-machine adjustment method. You need a flow meter and a pressure gauge with a minimum 6000 psi rating—the manual is tool-specific about that. It lists the target charge pressure (in psi, not bar—this is the North American version) and the max swivel angle. If your numbers don’t match, the manual tells you which shims to pull and how much backlash is acceptable. I’ve used this same procedure to bring a seized A6VM back to within 3% of factory flow. It works because the engineers didn’t assume you’d figure it out—they wrote it out, step by step, with no ambiguity.

Does This Manual Fit Your A6VM NG 28 Motor?

The manual covers the A6VM NG 28 variable displacement motor in series 63. That means the 28 displacement size (in cm³/rev) with the new generation housing. If you have an older model with a different series number, some of the torque specs and port layouts might not match. Check the identification plate on your motor. The product description chapter on page 11 shows the type code breakdown so you can confirm compatibility before you buy. This is not a generic hydraulic manual—it’s specific to the A6VM NG 28, and that specificity is exactly why it works on the bench. If you need documentation for a different Rexroth unit, look at the Bosch Rexroth A4VG56 Hydraulic Units Spare Parts List or the Bosch Rexroth A4VSO Variable Displacement Pump Technical Manual for pump-side work.

Audience: Who Should Have This on Their Bench

Home garage guys who are swapping a motor on their skid steer or excavator need this manual if they want the job to last longer than a month. Professional rebuild shops should have a copy in the binder for every A6VM they touch. If you’re a beginner, don’t open the motor without reading the safety section first—hydraulic pressure can turn a loose fitting into a hypodermic needle. The manual is written in both English and German, and the English side is clear enough that a motivated DIYer with a decent toolbox can follow it. But I’ll be honest: you need a torque wrench that clicks at the values in this book, and you need to own a set of pin spanners for the lock rings. The manual tells you exactly what tools are required, and it doesn’t sugarcoat the skill level.

On the other end of the spectrum, I still reference this manual when I’m training a new tech on Rexroth displacement controls. The checking chapter is the best classroom for understanding how the swashplate feedback loop works. You can learn more from 32 pages of factory procedure than from a hundred forum posts.

FAQ – Common Questions About the A6VM NG 28 Repair Manual

Does this manual include the full disassembly procedure?

Yes. It covers external subassembly exchange and internal checking/adjustment. The manual does not cover complete disassembly of the rotating group—that’s in a different document. For a full teardown, you need the service manual, not this repair manual.

What torque specs are included?

Page 15 and 25 list torque values for valve plate bolts, control cover screws, drain plug, and high-pressure relief valves. All values are in ft-lb and Nm. Because it’s an OEM manual, the torque table includes the lubrication condition (dry vs. lightly oiled).

Is the manual in metric units?

It’s metric by origin, but the North American edition has imperial conversions printed inline. The torque table gives both. The flow and pressure specs are in psi and gpm.

Can I use this for the A6VM 200 size?

The manual title says “A6VM NG 28-200”, which means it covers the entire series from size 28 to 200. The procedures are the same, but the specific shim stacks and torque values differ. Page 11 shows you how to read the type code to confirm your displacement. The manual includes data for all sizes in the range.

Why I Still Use This Manual

Three decades of turning wrenches and I have yet to find a third-party document that gets the A6VM control override procedure correct. The OEM manual covers the ESX control override sequence step by step. It tells you what happens when the control unit locks you out and how to reset the displacement limiter without damaging the swashplate bearing. That kind of detail is worth the price of the manual by itself. And because it’s an original factory document from Bosch Rexroth, the page layout is clean, the drawings are schematic but accurate, and there are no advertisements or missing sections. If you’re serious about keeping hydraulic equipment running, Manual Transmission fundamentals only go so far—you need the motor’s own repair manual to get the job done. Pair it with a Manual Transmission repair guide for the driveline, and you’ve got both halves of the system covered.

Get the factory data. Access the Factory Manual now from AutoRepairManuals and stop wasting billable hours on guesses.