Mercedes 722.6, Daimler W5, Porsche W5, Jaguar 722.6 - Transmission Digest

Mercedes 722.6, Daimler W5, Porsche W5, Jaguar 722.6

The 722.6 transmission went into production for use in 1996-model-year vehicles and is still being offered in 2009. The 722.6 is used in Mercedes, Porsche and Jaguar vehicles and in a variety of Chrysler products, where it is referred to as NAG1.

Mercedes 722.6, Daimler W5, Porsche W5, Jaguar 722.6

TASC Force Tips

Author: Mio Cundl

Shift problems caused by loss of line pressure

TASC Force Tips

  • Author: Mio Cundl

Shift problems caused by loss of line pressure

The 722.6 transmission went into production for use in 1996-model-year vehicles and is still being offered in 2009. The 722.6 is used in Mercedes, Porsche and Jaguar vehicles and in a variety of Chrysler products, where it is referred to as NAG1.

NAG is an acronym derived from the German for new automatic gearbox, the number 1 being the first version. In the U.S., NAG1 units include the W5A580, W5A380, W5A330 and W5J400. In the W5A series, the last three digits indicate the maximum input torque in Newton meters. The W5A330 has the widest gear ratio; the others have the same ratio. J400 identifies the unit as a Jeep application.

You can identify the origin by the following process: If the unit has only a pin stamp on the driver side, or a combination pin stamp and bar-code tag, it was manufactured in Germany. If it has only a bar-code tag, it was manufactured by Chrysler.

The Sprinter, Crossfire and Mercedes units require specific fluid because of calibration issues; the other Chrysler applications use ATF4.

This article focuses primarily on drivability issues related to the electro-hydraulic control unit or valve body. This gearbox was one of the first five-speeds with a new concept in load-sensitive working pressure and overlap clutch control. The converter was also unique because of its multi-disc torque-converter clutch (Figure 1).

All these advances require precise hydraulic control, which leads us to the problems discussed here. One of the drivability complaints involves engine-speed flare on a 2-3/4-5 upshift or a neutral flare on a 5-4/3-2 downshift. During upshift or downshift under load, line pressure (referred to as working pressure in the 722.6) must be responsive. The outer bore of the working-pressure regulator valve wears and allows the pMod solenoid-signal oil to leak past the boost end of the valve (Figure 2). As the casting wears, working pressure does not increase with engine load and the flare or loss of gear occurs.

In 1998, many of the high-mileage cars we repaired under Mercedes warranty had the same problem: 2-3 flare causing the vehicle to go into limp mode. After several inspections we discovered the link between the working-pressure bore wear and the shift problems. We believed that the lack of hardness of the valve-body material was the cause of this common failure. We designed a bushing to correct the leakage, using a harder material that would allow it to last longer when paired with a high-speed valve. The valve is a long, one-piece design, and when it is leveraged on the larger end, it also loads into the bore on the smaller inboard end. Both of these wear conditions can be discovered by either a vacuum test (Figure 3) or a visual inspection. Figure 4 shows a worn bore on the right and a repaired bore on the left.

The 1-2 /4-5, 2-3 and 3-4 overlap sleeves are also in the pMod solenoid-signal circuit (figures 5, 6 and 7). It is common for them to wear on the inside diameter and to leak at the outside diameter as well. Wear at any of these sleeves reduces pressure at the working-pressure valve. These sleeves can be vacuum tested prior to removal or cleaned and inspected for wear.

Mio Cundl is the owner of D.B. Automobile in Berlin, Germany, and a member of the Sonnax EURO-TASC Force (Technical Automotive Specialties Committee), a group of recognized industry technical specialists, transmission rebuilders and Sonnax Industries Inc. technicians.

You May Also Like

Sherlock Holmes Approach to an AB60 No-Move Situation

The effectiveness in diagnosing automatic transmission malfunctions is an art form. Although there are similarities among the wide varieties of transmissions on the road, each transmission has its own peculiarities. Aside from having mechanical, hydraulic, and electrical hardware systems to contend with, software/programming issues and various vehicle platforms make diagnostics much more difficult.  Using scopes provides

ab60

The effectiveness in diagnosing automatic transmission malfunctions is an art form. Although there are similarities among the wide varieties of transmissions on the road, each transmission has its own peculiarities. Aside from having mechanical, hydraulic, and electrical hardware systems to contend with, software/programming issues and various vehicle platforms make diagnostics much more difficult. 

GM 6T40 Pump Identification Guide

The 6T40 was introduced in 2008 for General Motors front-wheel-drive cars in the Chevrolet Malibu and has gone through several changes throughout its three generations, specifically in the pump area. The 6T40 is closely related to the more lightweight 6T30 and the heavier duty 6T45 and 6T50. Generation one started phasing out during the 2012

Seeing the Forest AND the Trees

They say that the proverbial phrase “I couldn’t see the forest for the trees” means that a person or organization cannot see the big picture because it focuses too much on the details. Related Articles – 4L60E Harsh 1-2 Shift – TASC Force Tips: Diagnosing 8L45 & 8L90 Shift Complaints – TASC Force Tips: Hydraulics

The Manifold Pipeway

The Honda six-speed transmission has been on the bench of many specialty shops for one reason or another (figure 1). But, for those of you who have yet to lay your hands on one, mounted on the upper side of the unit is one of the largest, if not the largest solenoid and pressure switch

8L90 Vacuum Testing

Below are the diagrams for vacuum testing GM 8L90 transmissions. Note: OE valves are shown in rest position and should be tested in rest position unless otherwise indicated. Test locations are pointed to with an arrow. Springs are not shown for visual clarity. A low vacuum reading indicates wear. For specific vacuum test information, refer

Other Posts

Shift of the shaft: Diagnosing Chrysler 48RE manual shaft issues

The TorqueFlite transmission has been around since mid-to-late 1950s. There have been many changes surrounding the manual shaft and rooster comb through the years. This transmission shaft controls the position of the manual valve that directs oil for the gear ranges, but it also is used for a Reverse light control as well as Park/Neutral

Diagnosing Ford 10R60, 10R80 and 10R140 series speed sensor issues

Ford 10-speed 10R series transmissions utilize four two-wire, Hall-effect sensors — TSS, ISSA2, ISSAB and OSS — for providing speed signals to PCM or TCM. They are supplied nine volts by a PCM or TCM and assist in the control of clutch apply/release timing that is used in determining shift quality, including TCC. Related Articles

Easy TH400, 4L80-E reverse servo setup: Craft your own tool

While not as sensitive as some shifting bands, the Reverse band adjustment on a TH400 or 4L80-E transmission is critical, and failure to get it right has tripped up even the best builders. There is nothing worse than getting the transmission installed, putting it in Reverse and then not going anywhere or having no engine

Understanding lube flow control valves in Toyota/Lexus UA/UB80 transmissions

The Toyota/Lexus UA80 and UB80 transmissions first came out in 2017 in Highlanders and Siennas. The UA80 is used in V6 applications, and the UB80 is paired with four-cylinder versions. They have been called Toyota New Global Architecture type transmissions, and alternately referred to as the “Direct Shift 8AT” eight-speed automatic transmission. This transmission was

Tasc-Tip-December-Figure-1---LFC-Valve-OE-Partial-Circuit-Diagram-1400