‘Petites Pièces, Gros Problèmes’ (little pieces, big problems) - Transmission Digest

‘Petites Pièces, Gros Problèmes’ (little pieces, big problems)

The story goes something like this: The customer came in to the shop complaining of no overdrive in a 4R70W. There are no codes or obvious external causes, but the complaint is verified on the road test. The unit will not go into overdrive.
‘Petites Pièces, Gros Problèmes’ (little pieces, big problems)

TASC Force Tips

Author: Serge Martin

TASC Force Tips

  • Author: Serge Martin

The language does not matter here. If you build transmissions, you know that little pieces of just about anything can cause big problems in an automatic transmission. This story may be brief, but it is important for two reasons. The first, of course, is that it is true. The second, and even more important, is that we have received several calls like this at our tech department.

The story goes something like this: The customer came in to the shop complaining of no overdrive in a 4R70W. There are no codes or obvious external causes, but the complaint is verified on the road test. The unit will not go into overdrive.

Teardown and inspection show nothing more than one small problem. The snap ring on the overdrive servo pin had broken into many pieces. With a new clip installed, the servo checked out fine and the transmission was put back together. The road test after the repair showed that the problem had not been corrected. Again, the unit will not go into overdrive. Back in the shop, we removed the valve body and found that a piece of the original snap ring was stuck in the overdrive-servo regulator valve.

Follow the trail traveled by the broken piece, as shown in figures 1, 2 and 3. It may seem hard to believe, but we have seen it more than once. Our message: If you find something broken, make sure to find all those little pieces. Protect yourself from those big problems.

Serge Martin is technical director of Matech BTA Inc., Quebec, and a member of the Sonnax TASC Force (Technical Automotive Specialties Committee), a group of recognized industry technical specialists, transmission rebuilders and Sonnax Industries Inc. technicians.

You May Also Like

Trying to Stop the Wheel Hop on Ford Edge with 6F50 Transmission

The 2014 Ford Edge SEL with a 3.5L engine (figure 1) and a 6F50 transmission can also be equipped with an AWD system. This would include a Power Transfer Unit (PTU) attached to the transmission with a rear driveshaft going to the Read Differential Unit (RDU). The RDU comprises a differential assembly along with a

The 2014 Ford Edge SEL with a 3.5L engine (figure 1) and a 6F50 transmission can also be equipped with an AWD system. This would include a Power Transfer Unit (PTU) attached to the transmission with a rear driveshaft going to the Read Differential Unit (RDU). The RDU comprises a differential assembly along with a viscous coupling assembly controlled by an Active Torque Control (ATC) coupling solenoid. The system is designed to monitor vehicle conditions continuously and seamlessly adjust torque distribution between the front and rear wheels. When it is functioning correctly, there should be no perception of this taking place when launching or driving the vehicle. 

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.  Related Articles –

ab60
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 – TASC Force Tips: Hydraulics Fundamentals: Check Valves – Shift Pointers: Mazda Sensitive to Pressure – Transmission Testing & Repairs:

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

Other Posts
GM 9T series: Critical wear areas, vacuum test locations

Sonnax has provided the following guide on critical wear areas and vacuum test locations for the GM 9T series of transmissions. Technicians working on these models should find this guide helpful. Related Articles – Shift Pointers: Sometimes, a repair needs a little more push – Less is more with cordless work lights – Are cell

TASC-Tip-1400
The torque converter can of worms: Lockup and aftermarket programming

Lockup torque converters have been around now for some time. They came into production around the time when fuel mileage demands were put into effect by the government, and the auto manufacturers needed to do something to better connect the fluid coupling (torque converter) of the automatic transmission to the motor. By doing this, OEMs

tascfeature-1400
Watch out for high pressure in GM 8L45, 8L90 valve bodies

Hey now! Oh boy, do I have a fun failure to share with you and warn you about today! Related Articles – The powertrain aftermarket: Growing and global – 6R80 whirring noise: TCC slip or engine surge? – The Subaru mystery burn Have you encountered a crack in the worm tracks in your GM 8L45

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