How I Resolved a No Forward or Reverse Condition on my 722.6 Transmission. W210 E55 AMG

I recently purchased a 2001 E55 AMG that would not move under it’s own power.

While that sounds daunting, the purpose of this article is to outline my approach to solving this issue, and highlight the relative ease with which this problem can be resolved with the right part, tools, and resources.

What's required for any vehicle motion? A lot of things, but in it’s simplest form, the transmission needs to create sufficient fluid PRESSURE. Fluid pressure and the ability to hold pressure is contingent on a few systems working properly. Those systems require:

  • Sufficient fluid ( I can’t tell you how many times I’ve had customers accidently fill the engine crankcase with transmission fluid and have no vehicle movement after a transmission service)

  • Functioning transmission pump

  • Functioning transmission seals

What are some checks that you can perform?

  • Fluid level - I created this video several years ago with FCP Euro showing you exactly how to check fluid level using the Mercedes transmission fluid dipstick tool.

  • Transmission pump noise - Audible whining from the transmission that changes pitch with RPM could indicate a broken transmission pump gear.

  • Fluid condition - Drain the fluid AND drop the pan to inspect the residual fluid and magnet. Very fine metal particles on the magnet that you can rub between you fingers with ease should not be cause for concern. Bright metal pieces or any fine metal that can prick you while inspecting the magnet is an indication of mechanical damage. Bright metal specs dispersed throughout the fluid is also cause for concern and represents mechanical damage. Large fluid droplets that seem to be dispersed in the transmission fluid is typically an indication of coolant contamination, sometimes referred to as glycol contamination, will require replacement of the torque converter as well as all frictions and seals. Coolant very aggressively damages transmission clutch pack friction material.

Coolant contamination 722.6 NAG1

So what did I find in my transmission during inspection?

  • Transmission was significantly overfilled (likely an attempt by previous owner to flush the transmission of contaminated fluid)

  • No audible or concerning noises from the transmission

  • Significant coolant contamination.

  • Fluid contamination of the transmission computer. This occurs when the case connector seal fails allowing transmission fluid to wick up the wiring harness to the transmission computer in the engine bay coffin box.

722.6 NAG1 Case connector seal failure

After coming to the realization that a donor/replacement transmission would be needed and that I would be fully refreshing the unit, I needed to source the “right” unit. Facelift W210 E55 AMG’s are equipped with the 722.636 version of the 722.6/W5A580 transmission. I needed a 722.6 W5A580 transmission that met the following criteria.

  • No park lock interlock linkage

  • Correct torque rating

  • Correct torque converter

  • Correct tooth counts for planetary gearsets

  • Correct clutch quantity count for each clutch basket

I chose the 722.633 transmission found in W220/215/R230 V8 models. They are cheap and plentiful, and the boxes in W215 models are typically low mileage. I sourced one from a recycling yard in New Haven, CT out of a 2001 CL500 at a cost of $320. Using this transmission meant my dipstick and output flange would need to be swapped. No other modifications would be needed. The following additional items are needed when refreshing a 722.6 transmission was coolant contamination issues.

  • Full gasket and seal kit 1402706500

  • OEM transmission filter 1402770095

  • Output flange nut 1409901150

  • Transmission case connector 2035400253

  • Snap Ring for K3 (this one always seems to deform when being removed) 000471035000

  • Rear output shaft case bearing 1409810125

  • ATF 236.10/12 or .14 transmission fluid.

  • Shift lever shaft bushings 2029920010, 0009944160 and 2109920010

  • Output flange from original trans (4 finger flange)

  • Dipstick from original transmission

  • Fluid dipstick tool for Mercedes (NAG1 dipsticks from Sprinter/Chrysler/ Jeep etc dipsticks are not compatible) 140589152100

  • Conductor plate 1402700861

  • Radiator 2105004703

  • Coolant G48

The replacement transmission was was disassembled, inspected, and cleaned. Full disassembly also included the inspection and disassembly of the valve body to confirm no bore wear, broken springs etc. I referenced factory service guides as well as industry service manuals for inspection guidelines, torque specs etc. I’ll be reserving all of that nerd-wizardry for a future article.

More of a visual learner? Southern Illinois University has a collection of videos on this transmission that provides a wealth of information.

722.6 OVERHAUL
























Kyle Bascombe