722.5 Overhaul Kit

If you drive a 1990s Mercedes-Benz S320, SL320 or 300SL with the five-speed automatic and it has started leaking from the pan, the front pump or the overdrive housing, or it now takes a long moment to pick up Drive when cold, you are dealing with a 722.5, and seal kits for it are much harder to find than for the four-speed or the later 722.6. This is a new 722.5 overhaul kit: the gaskets and seals needed to take the unit apart and put it back together leak-free. It is listed for 1994-1997 Mercedes applications including the S320 and SL320.

What the overhaul kit does in a 722.5

Mercedes built the 722.5 (factory type W5A 030) by taking the hydraulically controlled four-speed and adding a separate, electrically controlled fifth-gear overdrive section in its own housing behind the main case. That gives this transmission more sealing points than the four-speeds it grew out of: the main case, the pump, every clutch and brake piston, the shaft sealing rings, and then a second housing joint with its own clutch, brake and oil passages for the overdrive. Every one of those joints and pistons depends on rubber and sealing rings that are now decades old. Once they harden, oil bleeds off before it can fully apply a clutch or brake, and fluid finds its way out of the case. An overhaul kit replaces those soft parts together, so after a rebuild you are not chasing one leak at a time. It is a seal and gasket kit only; frictions and steels are sold separately in our 722.5 master rebuild kit.

Symptoms of worn 722.5 seals

• Fluid weeping from the pan gasket, the joint between the main case and the overdrive housing, or the rear output seal
• A leak at the bell housing that turns out to be the front pump seal or pump bushing, one of the most common 722.5 repairs
• Slow engagement into Drive or Reverse until the transmission warms up
• Slipping or soft shifts that get worse as the fluid gets hot, a sign piston seals are no longer holding apply pressure
• Reverse that engages late or harshly; rebuilders report weak reverse piston springs on older units, so inspect them while it is apart

How to confirm you need a reseal

Clean the case, drive the car, and find where the fluid is coming from before you order. A pan gasket or a single external seal can sometimes be handled on its own; leaks from several points, or a pump seal leak combined with slow engagement, point to a full reseal. Pull a fluid sample: if it is dark, smells burnt or carries friction material, the clutch packs are worn and you will want the master kit rather than seals alone. A sticking shift valve can also cause harsh or late shifts, so if the fluid is clean and the problem is shift quality rather than leakage, look at the 722.5 valve body. If you are comparing the 722.5 with its successor, our 722.6 common problems guide shows how differently the later fully electronic five-speed fails.

Fitment

This kit is listed for 1994-1997 Mercedes-Benz applications, with the S320 and SL320 named. The 722.5 was produced from 1990, and it was also used in the 300SL and the 350SD and 350SDL diesels in the early 1990s. It is not interchangeable with 722.3 or 722.4 four-speed kits, because those have no overdrive housing to seal. This is an unbranded kit, so match it carefully: confirm the transmission number stamped on your case starts with 722.5, and send us your year and VIN before ordering if you have any doubt. Earlier and later Mercedes units are on our Mercedes 722 collection page.

Install notes

• Soak piston seals in ATF and lubricate sealing rings with assembly gel before installing them.
• Inspect the pump bushing and the reverse piston springs while the unit is apart; replacing the seals without them often brings the leak or harsh reverse back.
• Air-check each clutch and brake, including the overdrive section, before final assembly.
• Replace the filter at the same time. The 722.5 holds about 8.5 liters in total, and a pan drain refills roughly 4 liters; use an MB 236.14-approved ATF and set the level hot.
• If teardown turns up a damaged shell, the 722.5 reaction shell is listed separately.

Will a 722.4 or 722.3 seal kit work on my 722.5?

No. The 722.5 adds a separately housed fifth-gear overdrive section to the four-speed design, so it has sealing points the four-speed kits do not cover. Buy a kit listed for the 722.5.

Which cars does this 722.5 overhaul kit fit?

It is listed for 1994-1997 Mercedes-Benz applications including the S320 and SL320. The 722.5 also went into the 300SL and 350SD/SDL in the early 1990s. Check the number stamped on your case and send us your year and VIN if you want us to confirm.

Does this kit include clutch plates?

No. It is the gasket and seal set. If your fluid is burnt or the packs are worn, the 722.5 master rebuild kit includes frictions and steels along with the soft parts.

What fluid and how much does a 722.5 take?

Rebuilder data lists MB 236.14 ATF and about 8.5 liters total capacity, with roughly 4 liters coming out on a pan drain. Set the level with the transmission at operating temperature.

My 722.5 leaks at the bell housing. Is that the transmission?

Often, yes. The front pump seal and pump bushing are among the most common 722.5 repairs. Confirm it is transmission fluid, not engine oil from the rear main seal, before you pull the unit.

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