722.6 Clutch Drum

This is a used original-equipment Mercedes-Benz clutch drum for the 722.6 five-speed automatic, pulled from the version of the transmission fitted to the W220 S-Class. If your S430, S500 or another 722.6-equipped Mercedes slips or flares on one particular shift, shows gear ratio faults, or you opened the unit and found a drum with a cracked housing, a spun bushing or a scored sealing ring surface, a known-good factory drum is usually a better repair than trying to salvage the damaged one. Because it is a used OEM part rather than a reproduction, it carries the factory casting, spline count and sensor window pattern for the transmission it came out of.

What a clutch drum does in a 722.6

The 722.6 makes five forward speeds and two reverse ratios from three simple planetary gearsets, three multi-disc brakes (B1, B2, B3) and three multi-disc clutches (K1, K2, K3), plus two one-way sprags. Each clutch lives in its own drum, and each drum does more than hold plates:

• K1 drum houses the F1 sprag, doubles as the hub for the B1 brake, carries the front sun gear and has the sheet metal windows that the n3 speed sensor reads.
• K2 drum is built as one piece with the input shaft and front internal ring gear, and its exciter ring feeds the n2 speed sensor.
• K3 drum sits at the rear with the F2 sprag and the center and rear sun gears, and is sealed by rings on the output shaft.

Every drum has a piston, a diaphragm return spring and a selective snap ring that sets clutch pack clearance. If the drum leaks apply oil or wobbles on a worn bushing, the clutch cannot clamp fully and the shift that depends on it slips.

Symptoms of a failing clutch drum

• Slip on the 1-2 shift or while holding second through fourth (K1), on the 2-3 shift or in third through fifth (K2), or in first, on the 3-4 shift and in reverse (K3)
• Gear ratio or implausible ratio fault codes and limp-home mode
• Delayed forward and reverse engagement, which on the K3 drum often traces to worn sealing ring surfaces on the output shaft
• Bronze bushing material or steel debris in the pan and on the filter
• Speed sensor faults after a planetary failure, because a damaged drum window can strike the Hall-effect sensor in the conductor plate

How to confirm the drum before you buy

Many 722.6 shift complaints are not hard-part failures at all. Worn valve body bores, a failed conductor plate and low fluid all cause flares and limp mode, so rule those out first with the steps in our 722.6 common problems and fixes guide. If the unit is already apart, air-check each clutch circuit with the drum installed on the pump tower: a strong, quick apply with no hissing means the piston and drum are sealing. A drum is the right buy when you see cracks, a spun or worn bushing, a damaged exciter window or ring land wear that a new sealing ring cannot fix. For a shift-by-shift diagnosis on the E-Class, see the 722.6 E-Class shift problems guide.

Fitment

This drum is listed for the 722.6 with a W220 S-Class reference. Mercedes built that S-Class from 1999 to 2005, mostly with V8 and V12 engines, and those engines use the high-torque versions of the 722.6 (the W5A 580 family) rather than the W5A 330 used behind 4, 5 and 6-cylinder engines. ATSG specifically warns that fitting drums or pistons from the wrong version, such as a 4-cylinder setup behind a 12-cylinder engine, leads to early failure. Before ordering, check which drum you need (K1, K2 or K3), compare the product photo with your old part, and read the transmission designation etched on the case. If you are unsure, send us your year and VIN and we will check it. You can see every 722.6 and 722.9 part we stock on the 722 transmission parts page.

Install notes

• Clean the drum, inspect the bushing and sealing ring lands, and fit new piston seals and sealing rings rather than reusing the old ones.
• Build the clutch pack with new frictions and steels, then set clearance with the selective snap ring. ATSG lists 0.5 to 1.8 mm for a 3 or 4-friction K1 pack, and the range changes with the number of plates and with each clutch.
• Air-check the piston before final assembly and inspect the planetary pinions for wobble; worn pinion shafts cause whine and can destroy the gearset.
• Refill with MB 236.14 approved fluid and do not mix it with other approvals.

Most drums get replaced during a rebuild, so pair it with the 722.6 W5A580 master rebuild kit for frictions, steels and seals. If the K2 side is the problem, we also stock a 722.6 input drum for 2000-2006, and a 722.6 planetary if the gearset shows damage.

Which clutch drum is this, K1, K2 or K3?

The listing identifies it as a 722.6 clutch drum from a W220 S-Class unit. Compare the product photo with your old drum, or send us your year and VIN, and we will confirm it is the drum position you need before it ships.

Will this fit my S430, S500 or CL500?

It comes from the W220 S-Class version of the 722.6, which in V8 and V12 cars is the high-torque W5A 580 family. Other cars using the same version are likely to match, but drums and pistons differ between the W5A 330 and W5A 580, so confirm the designation on your case first.

What should I replace along with the drum?

New piston seals, sealing rings, frictions and steels for that clutch pack, plus a filter and fresh MB 236.14 fluid. Inspect the planetary pinions and the bushings while the unit is apart.

Is it new or used?

Used original-equipment Mercedes-Benz, cleaned up and ready to install. Inspect the bushing and sealing ring lands before assembly as you would with any hard part.

Do I need to do an adaptation after installing it?

A rebuilt 722.6 should have its shift adaptations reset with a capable scan tool and then be driven so the TCM can relearn. Clutch clearance must be set correctly first, because no adaptation can fix a pack that is out of spec.

• 722.6 Common Problems and Fixes
• 722.6 Mercedes E Class Shift Problems: Diagnosis and Fix
• 722.6 Mercedes C Class Shift Problems: Diagnosis and Fix
• 722.6 Mercedes ML Common Problems and Fixes