Torque Converter Damage/ I.D. your converter

393394926well, one of my friends brought a tranny into my shop a few weeks back and i literally had to take a sledge hammer to it to get it out of the tranny. the whole center of the torque converter had dislodged and exploded the bearing. i actually watched him pull his car off the trailer at fall brawl and pull forward to lose all gears after 10 feet. not one of the best things in the world to witness as a transmission builder.

After going through the transmission it was obvious that the converter had ballooned- tearing itself apart internally and messing up the front pump assy. Ballooning is primarily caused by prolonged operation under excessive loading, very abrupt application of load, or operating a torque converter at very high RPM. the shape of the converter’s housing is caused to be physically distorted due to internal pressure and/or the stress imposed by centrifugal force. In drag racing, ballooning is something that high hp cars with a trans brake experience due to shock load of launch off the line. in derby, this happens when you slam shift with your foot on the throttle. in this case the guy got suck in a hole with a couple of imperials comming after him in his 74 buick…..can’t blame him!

in extreme conditions like a nitrous oxide set up with a trans brake, you would get a converter specifically made with what is called an anti-balooning plate, along with furnace brazing the internal fins. Basically the ballooning plate is a re-enforcement of the housing to help take the shock load. a lot of guys also refer to them as nitrous converters. However for most of us, Furnace brazing the internals of the converter alone is more than enough to strengthen up a converter- and reasonably priced.
as you will see in the pictures below, the balloon victim was a stock light duty converter. I took the converter over to my friends at Midwest converter and discovered a few things i didn’t know that are worth sharing. there are two different th400 13″ non lockup converters. look at the pictures side by side and you will see by the fin grooves of the first one they tilt to the left, and the other tilts to the right. light duty 400 converters….they called them V-6 converters have the fins tilted to the right at the edge and extremely light duty bearings internally. V-8 or heavy duty converters tilt to the left from the bottom up.


our friend with the 74 buick put in a weak converter from the get go. the sad thing is that he probably either bought it from a new parts supplier for cheap or pulled it out of a driver with a v-8. since the v-6 converters are pretty much worth nothing on core and cheap, they got used more often than not where they should not have been. And although a bit off topic i am under the impression that some of these cheap reman converters you get from your local cheapo parts house may be slightly ballooned from the get go. a dead giveaway that you are having a ballooning issue is the thing wobbles all over the place at idle, or a bad vibration. when a converter balloons it will not center between the pump and the center of the crankshaft.

393394925Here is a picture of the stator and front section (flex plate side) of the housing. as you can see all the fins absorbed damage, and the front support bearing is completely missing from the stator as it exploded and causes most of the damage to the fins. according to Dennis @ Midwest, what happened is the converter ballooned, caused the stator to dislodge and explode the bearing- which in turn caused all the fin damage. in a heavy duty/furnace brazed converter, these bearings are nearly double the size of this unit and all the fins ypou see are brazed in place not just crimped into the pieces that hold em together. the picture at the top of the page is of the snout side that faces the front pump. notice that the fins to the outside on both of the pics have the same effect like running your finger across radiator fins bending over the sheet metal. some of the fins are completely ripped out of place.

So what is the moral to the story……well there are several points here. A well built furnace brazed heavy duty converter is absolutely critical for demo derby. light duty, stock replacement, cheap reman, and used converters will take you out….and it will piss you off completely when it does. so no matter who builds your tranny, take caution if they want to sell you a converter that is not heavy duty. i use converters from Midwest, B&M, TCI,and Coan. Most all of them make a stock reman converter for around 75-100$ that is not furnace brazed. so don’t be mistaken that just cause it has a big name manufacture name on it that it is good to go. AND if you go to your local parts house you may indeed get just about anything for 75 bucks including the weak P.O.S that was described earlier in this post. food for thought good luck!

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