Torque Converter Tech Tip Archives - Page 2 of 6 - Transmission Digest
Premature Failure of Mitsubishi Galant Ring Gears

Torque-converter rebuilders have been reporting an increase in the number of failed ring gears on Mitsubishi Galant converters. Most of the failed ring gears are found on 2006-08 vehicles equipped with V-6 engines, and the failures seem to occur soon after the vehicle’s starter has been replaced.

Mercedes 722.6: Cold Stall/TCC Shudder

For several years, technicians have been trying to solve the mysterious cold-stall issue in vehicles equipped with Mercedes 722.6 transmissions. When the problem was first identified, it was thought to be associated with aftermarket components. At that time, no one had seen the problem in a vehicle that still had only original equipment.

Taking the Fear out of Rebuilding the New GM Captive Clutch

The new General Motors captive clutch has four spring-steel straps that restrict the rotational movement of the piston. One end of each strap is riveted to the piston and the other end is riveted to the cover (figures 1a and 1b).

More Torque-Converter Forensics

Try to imagine the difficult job tech-line technicians have. They are asked to decipher bits and pieces of information that may not be accurate and then come up with the correct answer. The information the technicians collected for the following two scenarios seemed to be as different as night and day. The information even originated in different countries. The amazing thing about these different complaints and symptoms was that they all had the same root cause.

Finding the cause of Honda 740 codes

Many converter shops have reported having Honda converters returned to their shops because of 740 codes. In most instances, the remedy was to install a new OEM converter.

Checking for Cracks

Attendees at the 2009 Torque Converter Rebuilders Association (TCRA) seminar in Tennessee were introduced to a couple of interesting methods of checking torque-converter covers for cracks.

Allison 1000 Converters – the Next Generation

The Allison 1000 converter has evolved considerably throughout its existence. By the end of the 2007 model year there had been five different generations of this converter. The chart in Figure 1 lists the part name, stall torque ratio, part number and color ID code for the first five generations of this converter (Transmission Digest, November 2007, page 47).

Orifice Control Within the Converter, Part 3

The secondary path of the charge/TCC-release oil is regulated to some degree by transmission parts within the confines of the converter. In some units, the charge oil is regulated by the orifice created between the raised area on the stator shaft (or support) and the impeller hub. In other units, it is regulated by restricting the flow of oil through or around the input-shaft bushing mounted inside the stator support. The Allison 500 series is a unique example because it uses both methods to regulate oil flow, as it both enters and exits the converter.

Orifice Control within the Converter, Part 2

Most torque-converter rebuilders understand how oil flow within the converter harnesses engine torque and helps drive the vehicle. Unfortunately, many rebuilders have little knowledge of the many secondary paths and functions of converter oil flow.

Orifice Control Within the Converter

Converter rebuilders want to know why some of the pistons have the orifice and some do not. The answer to this question begins with understanding why the orifice was used in the first place. The orifice was drilled through the piston to help cool the mass of the converter. The TCC-release passage is open to exhaust when the converter is in the TCC-apply mode. Metered oil, which is allowed to bypass the piston by way of the orifice, carries some heat away from the converter.

Change May Be Good – But Be Careful

In the following situations each converter builder made what he believed to be a single change. For each of them, the change did not seem to cause any problems at first. Unfortunately, devastating long-term consequences occurred in both situations because they failed to realize that they had made more than one change.

Cummins Diesel TCC Shudder: a New Twist

A 2001 Dodge Ram 2500 4×4, with a Cummins diesel engine and a 618 transmission, was brought to a transmission shop with a complaint of TCC shudder. Three to four months prior to coming to the shop, the customer noticed a change in the TCC-apply feel. He said that the TCC apply had suddenly become more aggressive or abrupt. The condition had worsened over the course of three to four months, until the start of the shudder issue.