722.5 Shift Kit

The 722.5 is the rarest member of the Mercedes-Benz 722 hydraulic family: a five-speed built on the 722.3/722.4 design with an added overdrive ratio, used in a limited number of gas-engine cars in the early 1990s. Parts are getting hard to find, and owners searching for help usually describe the same thing: a hard thump into second, a 2-3 that slips until the car warms up, or a mushy shift into the upper gears. This page covers the Superior K722A-G shift correction package, which Superior catalogs for gas 722.3, 722.4 and 722.5 transmissions built from 1980 to 1995.

How the kit works in a 722.5

Shift timing on a 722.5 is purely hydraulic. A governor driven by the output shaft and a cable from the throttle decide when the box shifts; a vacuum-operated modulator on the case decides how hard. That modulating pressure is routed through the valve body to every clutch and band. Because the 722.5 shares its control layout with the four-speed units, it also shares their weak spots: an abrupt 1-2 and soft, slippery upper shifts as springs tire and valves wear.

The Superior package corrects the valve body calibration rather than just raising pressure across the board. Its stated targets are a harsh 1-2 shift, soft or flaring 2-3, slip or flare on the 2-3 when cold, and a soft or flaring 3-4. Taking the bang out of the first shift while firming the next two is what makes it popular for daily-driven cars, and it includes the parts needed to get the modulating pressure set properly afterward.

Symptoms that point to this kit

• A thump or bang on the 1-2 shift, worst at light throttle from a stop
• 2-3 shift that slips or flares cold, then improves once fluid is warm
• Slow, soft 3-4 shift with an engine rpm flare
• Shift feel that changed after a modulator was replaced or adjusted
• No stored codes despite obvious shift faults, normal for this hydraulically controlled unit

Diagnosis first

Before opening the valve body, test the vacuum supply. Mercedes Technical Bulletin 259, written for the 722.3, 722.4 and 722.5, warns that the modulator's rubber cap is a sealing part, not a dust cover, and that a leaking cap produces harsh or erratic shifts. Put a hand vacuum pump on the modulator fitting; it should hold 14 inches or more. If shifts are too soft or too harsh in every gear, the factory calls for a pressure gauge on test port M to verify modulating pressure. A healthy vacuum circuit plus the harsh-low, soft-high pattern means the valve body is the problem. Overdrive complaints on later electronic cars have different causes; our 722.6 won't shift into overdrive guide explains those, and the E-Class shift problems guide helps confirm which family your car belongs to.

Fitment

This is the gas-engine version of the kit and covers the 722.5 along with the 722.3 and 722.4 for 1980-1995. It does not fit diesel units or the later electronically controlled 722.6. Because 722.5 production was short and valve bodies changed during the run, read the transmission number from the identification tag on the case before ordering, or send us the year, model and VIN and we will confirm. Owners of the four-speed should order the 722.4 shift kit listing instead. Other parts for this family are in the 722 series collection.

Install notes

• Drop the pan and remove the valve body in the car; keep every spring with its valve, since several are close in size.
• Follow the kit's instruction sheet step by step and read it fully first.
• Expect to reset modulating pressure afterward. Per the factory procedure, a full turn of the older modulator's adjusting screw is about 0.4 bar (5.8 psi), and on later units each detent of the locking key is about 0.2 bar.
• Use a new pan gasket and filter, and refill with the ATF listed in your owner's manual.
• Worn governor or pump parts cause their own shift timing problems; the 722.5 governor and pump parts set is worth a look if your shift points are wrong, not just the shift feel.

Is the 722.5 kit the same as the 722.4 kit?

Yes, Superior's K722A-G covers gas 722.3, 722.4 and 722.5 transmissions from 1980 to 1995. Confirm your transmission number before ordering.

My 722.5 slips on the 2-3 only when cold. Will this help?

Cold slip or flare on the 2-3 is one of the specific conditions the kit is built to correct, provided the clutches are not already worn out.

Can I use it on a diesel?

No. This is the gas calibration. Diesel units need the separate diesel package.

Why does my 722.5 not set any trouble codes?

It is hydraulically controlled with no transmission computer. Diagnosis is done by road test, vacuum test and pressure gauge.

Do I need special tools?

Basic hand tools for the pan and valve body, a hand vacuum pump to test the modulator, and ideally a pressure gauge for test port M when setting modulating pressure.

• 722.6 Won't Shift Into Overdrive: Causes and Fix
• 722.6 Mercedes E Class Shift Problems: Diagnosis and Fix
• 722.9 Harsh Shift Causes and Fix