TCRA© - March - 2017

TCRA Introduces Torque Converter Specification Standards

One of the difficulties in dealing with people from around the world — and even sometimes just over in the next county — is that people often identify things differently. Maybe you remember the old Gershwin song, Let’s Call the Whole Thing Off, “You like tomato and I like tomahto…”

Speaking differently can also affect the transmission industry. Around here, we call them “Zee”-F, while the British use “Zed”-F. These minor differences are one when we’re speaking, because eventually we can work out what they other is trying to say.

But when we’re talking about specifications and measurements, what you say is just as important as the procedures you use. One slight difference can change the entire result.

To avoid these discrepancies, the Torque Converter Rebuilders Association (TCRA) Technical Committee has put a set of specifications together to standardize the way that torque converters are measured, both externally and for internal adjustments.

So what does this mean for the transmission rebuilder? It means that your local TCRA Member has access to a set of standards to refer to when they’re faced with a rare unit or one they haven’t seen before.

In today’s transmissions, there are a number internal torque converter components that can affect the way the converter works. Just as in the transmission, correct lockup clutch clearance will have a dramatic effect on TCC apply and release, which of course will affect its performance in your transmission. Other components that can affect converter performance are the stator fin count and angle, and the vane angle.

When you look at a converter catalog, you’ll see terms such as hub style, mounting type, bolt circle and maybe lockup yes/no. Most of these choices are obvious and there isn’t a lot of room for confusion, but you need to make sure that you’re using the same names for the same converter parts (figures 1 and 2).

When it comes to clearances and other measurements, everyone needs to follow a standard procedure. Many of the standards developed by TCRA relate to internal measurements; they’ll only apply to the rebuilding process. But when choosing the right converter for your transmission, you’ll need to verify the converter by its external specifications, such as overall height, hub length, and so on.

Here’s how to check the overall converter height (figure 3):

  • Set the converter on a flat surface, with the pilot protruding through the surface. The easiest way is to have a hole drilled in your workbench for the pilot to fit through, but you can use spacers to raise the converter. Just make sure you raise it evenly.
  • Measure the overall height to the end of the hub. If you used spacers to raise the converter, make sure you subtract that amount from your overall measurement.

Always measure to the highest point of the hub. When measuring a converter with a tang-type hub, measure to the top of the tang.

To measure hub length (figure 4), measure from the end of the hub to the flat area of the impellor; not the weld.

Finally, consider stall speed. On converters with ribs (figure 1), you can identify the different stall speeds by the angle of the ribs. While this doesn’t give you an exact measurement, it will allow you to compare stall speeds between two different converters; the greater the angles of the ribs, the higher the stall speed.

Of course, there are other elements that affect stall speed, but they’re internal, such as differences in the stator. Converters with a smooth body aren’t quite as easy to identify; for them, you’ll have to depend on the converter rebuilder to supply the correct converter for your application.

So, whether you speak with a different accent or a different language, or even just disagree on the proper way to pronounce “tomato,” using standard terms and measuring methods will mean that we’re all speaking the same converter language.