Shift Pointers Archives - Page 5 of 18 - Transmission Digest
A Sudden No Move

It’s always unsettling when a transmission comes back after the customer has had it for only an hour; especially when it came back on a hook. Such was the case at a local transmission shop with a 42RE transmission.

7 G-Tronic Plus Generation Six – Part 1

Mercedes’ 7-speed transmission known as the 7 G-Tronic is commonly referred to as the 722.9 transmission. This 5th generation of Mercedes’ transmission lineup made its first appearance in 2003. By 2010 a revised version of this transmission was developed making it the 6th generation of transmissions calling it the 7 G-Tronic Plus.

TCC Engine Surge

A 2008 Honda Accord using the B97A transmission behind a 3.5L engine was brought to Newmarket Transmissions from a general repair shop to be rebuilt. They had changed the radiator and when topping off fluids, they noticed the “strawberry milkshake” condition of the transmission fluid. The radiator was also contaminated with the milkshake condition as seen with the deteriorated cap in Figure 1.

6L80 Filter Crush

The transmission we are talking about is the 6L80 family of transmissions. It’s quite surprising to know the many times we have encountered this installation error. It is essential that the entire pan be fully supported by a saddle to distribute the pressure evenly across the bottom of the transmission. This will prevent damage to both the pan and filter resulting in immediate failure of your rebuilt transmission.

Beware of Code P0720: Part 2

When the computer observed an increase in rear prop speed as a result of the axle popping out, it determined the front vehicle speed sensor as being faulty due to it decreasing in rpm. Of course the loss of rpm was due to the loss of power. The computer either didn’t or couldn’t distinguish the difference. Nonetheless, the front vehicle speed sensor was being blamed when nothing was wrong with it or the transmission. Considering the strain this had on the transfer clutch with the axle popping in and out, it explains why they were burnt originally.

Programming: A Blessing or a Curse

(Re)programming and tuning do share some similarities but are very different and shouldn’t be mixed up. As told in the previous chapter, the program contains a lot of info including the mapping. This mapping is basically the way the car drives “transmission-wise.” This mapping contains stuff like shift speeds, TCC strategy and speeds, shift firmness and pressures.

Programming: A Blessing or a Curse

To answer the question in the headline, we need to look at the programming of modules. Not the actual program, but the foundation on which it is based on.

Make a New Friend: Programming

The automotive sector is rapidly following the IT sector and becoming more complex by the minute. To shed some light on this trend, I will discuss programming in a series of articles.

Hot Head

A 2000 Mercury Grand Marquis with a 4.6L engine using a 4R70W transmission is at a general-repair shop for weeks. The problem is an intermittent engine surge on top of the 1-2 shift when hot. The perception is an engine problem. Eventually, the idea of the converter clutch coming on was being considered. Without much testing, the valve body and solenoids were replaced yet the problem persisted.

Fretting Revisited

Nonetheless, while conducting a seminar recently, an ATSG member who was there approached me with a manual transmission concern. The complaint he had with it was difficulty engaging the transmission from a standing start. It acted as if the clutch pedal was not fully releasing the pressure plate. Yet it seemed to shift through the gears OK once the vehicle was in motion. No work had yet been performed, and from all appearances, it seemed that the clutch pedal was functioning correctly.

Beware of Code P0720

Subaru’s TG5D9 transmission utilizes four different speed sensors, two of which are inside the transmission and two are externally located. When a code P0720 for a front vehicle speed sensor is set, the most-forward external speed sensor is replaced – yet the code remains. The wiring is checked and the signal is checked and all looks fine. The TCM then gets replaced but P0720 remains.

Remembering Your ‘A’ Game

A 2003 Saturn L300 came in with CAN BUS communication problems producing codes U1000 and a U2105 (Figure 1). U1000 is a Class II Data Link code. One explanation given for this code by GM is that should this code be set in history with other DTCs set in “current or history,” to diagnose these codes or code first. This means DTC U2105 could be the cause of code U1000 and will need to be diagnosed and resolved first. It is learned that code U2105 will set if the BCM or TCM lost CAN communications with the ECM.