Torque Converter Tech Tip Archives - Page 5 of 6 - Transmission Digest
Myth Busters

When the vehicle manufacturers create their driveline packages, they have many issues to consider, such as fuel economy, performance and durability. In the torque-converter-rebuilding industry, many companies will make modifications to enhance the OEM torque converter for a specific vehicle combination. Some modifications are done to create better acceleration and others are done to improve towing capabilities and fuel economy.

Lockup Surge in Allison 1000s

Have you ever found yourself chasing a “phantom” TCC drivability problem in a GM vehicle that uses the Allison 1000/2000/2400 series of transmissions?

If you have, there’s a good chance that the root of your problem turned out to be the torque converter. No earth-shattering news there, but what is unique is that the problem was likely on the outside of the converter, not the inside.

Revisiting the Captive Clutch

Joe Rivera proved that the ZF 5HP19/24 converter with captive clutch is rebuildable (see “Rebuilding the Unrebuildable,” Transmission Digest, December 2005). Many converter shops are now trying to build this unit, and the number of rebuilding questions continues to increase. A recent rise in issues related to lockup performance after rebuild has prompted a closer look at this unit. The same fear factor that prevented many shops from trying to rebuild this unit in the first place is now causing some of the braver rebuilders to have second thoughts.

Replace Those Honda Stator Bearings with Something More Readily Available

Many late-model Honda converters have unique stator bearings. The caged-roller part of the bearing is like the bearing used in the JATCO RE4R01A converters. This part of the bearing is not unique. The outboard races of the stator bearings also are not unique. The impeller-side bearing runs against the flanged impeller hub, and the turbine-side bearing runs against the turbine hub. It is the bearing races on each side of the stator that are unique (see Figure 1).

Converter-Charge Mysteries

Converter charge oil performs a number of important functions: It fills the converter in a timely manner. It keeps the lockup clutch off the cover in the release mode. It also eventually becomes the lube oil for the transmission.

The Proper Surface Finish for Bonding (an Eye Opener)

Choosing the correct surface finish for bonding can be controversial. Some rebuilders claim you can bond to a surface as smooth as glass, provided the bond-line temperature and the compression pressure are correct. Others claim that a very rough surface finish is needed for a good bond. The finish of a machined surface is rated on a roughness-average (RA) scale.

Changing Converter Designs Change Your Approach

The 10-inch front-wheel-drive Chrysler converter used in the 604 and 606 (41TE & 42LE) transmissions has undergone some changes in recent years. From the outside you can see that the surface of the impeller, smooth on the earlier models, now has dimples (see Figure 1).

2002-Up 5R55N/S/W Converter Noise: One Shop’s Solution

Converter shops around the country are seeing an increase in complaints about the late-model 5R55N/S/W converters; more specifically, the noise they make. These noises are described as a clattering sound, often compared with the sound made by the early E4OD multi-clutch converters. The sounds seem to be made by metal-to-metal contact, and all disappear when the TCC is applied.

Identifying the 722.6 Converters

Mercedes has used the 722.6 transmission in a number of different vehicles and in combination with different engines. To accommodate these different vehicle and engine combinations, different converters were needed. Many of the converters were similar in appearance and differed only in their bolt circle or diameter.

Water Contamination in Torque Converters

Opening up a torque converter and finding what looks like a strawberry milkshake inside is fairly common in the rebuilding industry. The strawberry-milkshake appearance is the result of ATF being contaminated by water. A small amount of water mixed with transmission fluid will change the appearance of the fluid dramatically. Since many shops have limited areas available for storing cores, some cores are open to the elements. Transporting cores in open vehicles also increases the opportunities for water contamination.

A Different Fix for an Old Problem

The problem of bore wear on torque-converter-clutch pistons has been around since lockup torque converters were born. The rotational restriction on the pistons is handled by splines, pins or fingers. But centering the pistons is generally the sole responsibility of the bore. Any out-of-balance movement of the piston will cause the piston bore to scuff against the turbine hub when it moves to apply or release the clutch. Indexing the piston to the turbine and balancing this unit helps minimize bore wear. (See the article on indexing TCC-piston damper assemblies to turbines, Transmission Digest, March 2006.)

Getting Your Cores Back

When torque converters first transitioned from the early bolt-together units to the welded/sealed units of the present day, transmission shops were faced with a new challenge. Most customers weren’t willing to pay for a new OEM converter on top of the cost of a transmission overhaul. The only alternative available at that time – reusing the customer’s original converter – seldom saved the customer or the transmission shop any money. More often than not, reusing the original converter created new problems when contamination from the original failure entered the newly overhauled transmission.