September 2007 Archives - Transmission Digest
Manual-Transmission Theory: Back to Basics

On automatic transmissions, engine-related computer problems can affect transmission operation. Computer-controlled vehicles have very complex electronic circuits and multiple computers, all of which need to work together. That being the case, we will start with the basics of rear-wheel-drive manual-transmission function and proceed to more-complex diagnostic issues with transfer cases and front-wheel-drive manual transmissions in the next series of articles. Transmission designs may vary in size, shape and appearance, but all the units function in the same manner.

September 2007 Issue

Issue Summary:

A 1995 or earlier Isuzu, Chevy or GMC truck with the JR403E may have no engine-braking assist from the exhaust-brake system and also may have an intermittent no-crank condition and/or difficulty starting.

A Honda vehicle may come into the shop with code P1298 in addition to one or more solenoid codes stored.

On a 2003-04 Honda Accord, 2002-04 Element or 2002-04 CR-V with automatic transmission, the manual shift lever cannot be moved from the park position after replacement of the throttle body.

After replacement of the EPC solenoid in a Ford 4R70W/4R70/75E, the transmission slips or chatters at times. A line-pressure check reveals erratic line pressure.

Volkswagen’s Direct-Shift Gearbox Part 5

The DSG valve body is definitely one of the simplest we have seen in transmissions (see figures 1 through 5). It contains only five valve line-ups, two checkballs, three damper assemblies, two pressure senders (pressure sensors/transducers) and 13 filters (see figures 2, 3 and 5).

Food for Thought: How Hot Is Hot?

How long have you been in the transmission business? Have you ever honestly sat down and thought about how an automatic transmission heats up? I mean, how hot does it get and how fast does it get there? Does the temperature stabilize as it does in an engine, or is it always changing? Have you ever taken a car for a nice long drive to be sure you “got it hot” and not been able to reproduce the problem? I’m sure you always figured that stop-and-go city driving creates more heat than driving on the highway, but how much more?

Shift By Wire

This article presents a situation that ATSG technical adviser Gerald Campbell handled regarding a ZF 6HP26 in a BMW with Reno Partipilo, Sal Scardina and Joe Russo from Continental Transmission in Bridgeview, Ill. But before we can cover it, we first need to present a bit of information that will help to make sense of the problem and what it was that corrected it.

Cleaning a difficult area

If you were raised in a religious family you probably heard that “cleanliness is next to godliness.” If you happen to be the parent of a 4-year-old, you’ve learned that cleanliness is next to impossible. In the transmission industry, cleanliness is a necessity. One small particle can stick a valve or cause a solenoid to malfunction and turn an otherwise perfect job into a nightmare.

A Word to the Wise Had Better Be Sufficient

In Hollywood they say that anytime you can get your name in the papers or other media it’s good publicity no matter how bad the incident. The idea is that even if you’ve done something horrible, the curiosity seekers will want to hear or read about it and then come to see the person who did it in their next public appearance. That may be fine for Hollywood, but it doesn’t work in the automotive business.