Cracking the code on furnace-brazed converters As torque load demands on converters increase, the need for stronger torque converters has also increased. OE manufacturers are furnace-brazing more of their converters to help meet this need, and it has become more critical to be able to identify them. In the early days the cut-and-look method was the only way to tell the difference between them. This option is often time-consuming and as the number of furnace-brazed converters increased, the odds of finding one quickly increased greatly as well.
Dacco’s latest catalog includes some handy furnace braze information in the 298mm section. If the I.D. code on your converter is visible, you can use the second digit to not only determine the stall of the converter, but also to tell if it is furnace-brazed or not. This I.D. method works well on most late model 298mm converters. It’s a good bet that if the second letter of the code is a C, H, K or L, your converter will have a furnace-brazed impeller. You may also notice than on the late-model 298mm converters, the majority of the I.D. stickers in a solid color will have a furnace-brazed impeller and the majority of the stickers with stripes won’t. Unfortunately, neither is foolproof enough to use as an identification process.
But one of the winners of the “Help Break The Code” contest has provided a missing link. Jesse Campbell from the Colorado Converter Co. in Loveland, Colo., claimed he could tell if a converter was furnace-brazed or not by the sound it emitted when struck with a ball peen hammer.
Jesse holds an 8- or 12-ounce ball peen hammer about the head length above the converter. Holding the handle loosely, he lets the hammer fall. The hammer strikes the converter between the two dimples, on the middle row of dimples, on the impeller side of the converter. A dull muffled sound tells him the converter is not furnace-brazed. A furnace-brazed converter will have a crisper, sharper ringing sound.
If you have ever worked in a transmission shop this would be a good time to strike yourself on the forehead with the palm of your hand. Transmission shops have been using this trick for years to tell if 700 pump rings were hardened or not. Why didn’t we think of this earlier? With a little bit of practice anyone can become proficient at finding the furnace-brazed core.
Here’s a word of caution when you are trying out this method. As we all know, with the possible exception of some late model AODE/4R70W converters, the Ford 12” impeller was never furnace-brazed. When you are mastering the ball peen method, you’ll find some C6 or AOD converters that emit a sound similar to a furnace-brazed impeller. What you are hearing is not an exception to the furnace-brazed rule, but a way to tell if the vanes are tight in the 12” Ford impeller. An impeller with good tight vanes will emit a dull muffled sound, just as you would expect. What you would not expect is that the looser the vanes, the more similar the sound is to that of a furnace-brazed impeller. This is a win-win situation. Not only can you tell if an impeller is furnace-brazed or not, you can also tell how tight the vanes are.
When some of the members of the Board of Directors for the Torque Converter Rebuilders were testing Jesse’s method, Don Randolph of Dacco, Inc. said that he could tell if a 298mm impeller was furnace-brazed just by looking at it as he walks by. Don went on to correctly identify six out of six converters. We were beginning to think that he might have psychic powers before he revealed his secret.
Don explained that the vane helps to strengthen the impeller. When the impeller goes into the furnace braze oven, the impeller shell dips slightly between the dimples. An impeller that has not been in an oven will be straight across between the dimples.
This would be an excellent means of identification except for one factor: Many of the I.D. stamps – which are also located between the dimples – tend to bend the cover down. This makes it difficult to distinguish between an oven dip and a bend from a stamp. But you can be sure that all of the converters that do not dip between the dimples will not be furnace-brazed.
The information provided by Jesse Campbell has won him a winner’s certificate in the “Help Break the Code” contest.
– ©2006 Sonnax Industries, Inc.
– Found in July 2006 Newsletter