Diagnosing Transmission Problems
The GM 298mm Converter

You’ll hear some convincing arguments about how the selective (conical) plastic thrust spacer is used to adjust the stack height on the GM 298mm torque converter. You also will hear some convincing arguments about how this same selective thrust spacer is used to adjust the clutch-release clearance on the GM 298mm converter. The truth is that both statements are correct. The selective (conical) plastic thrust spacer may be used to adjust both the stack height and clutch-release clearance on this converter. What is important is to be aware that changing the adjustment of one also changes the other. As long as you know the proper parameters and parameter limits of both measurements, you can adjust both successfully.

Steptronic, Tiptronic, Geartronic – Ah, What’s the Difference?

I am always amused by the many different names we see that are used to describe basically the same device. For example, we have a pressure-control solenoid, or we could call it an EPC (electronic pressure-control) solenoid, a force motor or a linear solenoid. We have the same thing with what Chrysler has called an Autostick, which now is being referred to as a J Gate, Steptronic, Tiptronic or Geartronic – how Ironic (see Figure 1).

Understanding Synchronization

One of the least-understood and most-commonly misdiagnosed complaints/problems with manually shifted transmissions and transfer cases is synchronization.

12-Valve Cummins Diesel/618 Transmission

A 1994 Dodge R2500 pickup was brought to a transmission shop. The customer complaint was no overdrive when cold and that as the vehicle got up to operating temperature the overdrive would engage but would go in and out with throttle opening.

July 2005 Issue

Issue Summary:

2000 and later Isuzu Trooper and BMW models with the 4L30-E transmission may exhibit diagnostic trouble code P1870 (torque-converter slip) or a shudder on TCC application.

Hyundai’s A4AF3 and A4BF2 units, used in 2000 and later Accent, Elantra and Tiburon, are almost identical to the A4AF1 and A4AF2, but with a few major exceptions.

After rebuild of a Hyundai A4AF3 or A4BF2, there is no forward movement in the Drive range, but reverse and manual low are OK. The transaxle may engage in Drive during high engine speeds, then neutral out and stop operating.

The Trooper Blues

The description for code 37 says this “serial line” is the wire that is connected from the transmission control module to the engine control module and the diagnostic connector. This wire is used for torque management. How it works: The TCM delivers a spark-advance signal to the ECM during each shift, through this serial line, to reduce engagement shock. Any interruptions, shorts or opens on this line will set a code 37.

Gear Head

Our instructor began by teaching us that a simple planetary gear set consists of 1) a center sun gear, 2) a carrier with three or more pinion gears that are free to rotate on their pins around the sun gear and 3) the internal ring gear, which meshes with the pinion gears. Then he started to say, “If you hold the internal gear stationary and drive the sun gear, you will see the pinions drive the carrier in the same direction as the sun gear but at a reduced speed with increased power.” This is where some of my fellow classmates started to get bored.

Getting Up to Speed

There are basically three different styles of speed sensors a transmission diagnostician has to deal with: a reed switch, an AC generator (pulse generator) and a Hall-effect sensor.

GM’s Steady-State Adapts

With a basic understanding of TAPS, the Transmission Adaptive Pressure System, covered in last month’s article, we will now try to tap into the Steady State Adapt System and what its data can tell us. Not all scan tools provide steady-state data, but I’m convinced that this information is a real help in diagnosing problems in the later GM units. Data for the examples I used in these articles was recorded on either my GM Tech2 or my Mastertech. All the units in the examples shown below are 4T65-Es.

Up to Standards

The cliché “What you don’t know can’t hurt you” is way out of date. The single most-important commodity in the world we operate in is knowledge. Information – and that means good, factual information – is the only thing that stands between us and expensive failures. Our quest for information will include a good working knowledge of the operation of the complex systems that comprise the modern motor vehicle and their relation to one another, feedback from the customer to fully understand their problem and the results they want you to achieve, and a thorough and complete observation of the vehicle you are working on.

Another Cross-Connect Scenario

1998 to 2000 Kia Sportage and Sephia have the idle-air-control valve and the throttle-position sensor relatively close to each other. Figures 1 and 2 show the setup in the Sephia, which is similar to that in the Sportage.

June 2005 Issue

4T65-E
Differences Between GM and Volvo Applications

The 4T65-E transmission is used both in General Motors vehicles beginning in 1997 and in Volvo 80 series starting in 1999. There are several major differences between these units that can cause some problems with parts interchangeability.