How close is close enough?

Ever wonder why a factory OEM torque converter lasts 150,000 to 200,000 miles repeatedly and a rebuilt converter may only go 75,000? This question has been asked by transmission shop owners, car owners and torque converter rebuilders alike. I believe we all know some of the reasons.



If a roller bearing has a mathematically predictable life cycle of 85,000 miles and the converter core has 100,000 miles on it when the converter rebuilders gets it, premature failure will probably occur if you reuse it because it “still looks good.” Now how about that clutch liner? It looks good right? How about the impeller hub, O-rings, seals? I think you see where this is going. You cannot warranty a torque converter 100% if you only replace 40% of the known consumable parts. That is a setup for a 60 % parts failure. These parts are known to have a cycle life. Companies such as Tri-Component and Sonnax Industries have spent an enormous amount of time, energy and money to provide you with replacement parts for these highly recognized parts prone to failure. Many times these replacement parts may be higher quality than the OEM.

So why do we not replace these parts? Whose fault is it? This “blame” can be tracked back to the end user. He or she wants their car or truck repaired as cheap as they can. So the transmission shop demands a lower priced product which in return puts the pricing and quality onto the back of the converter rebuilder. For the most part he only cares that the converter works when it leaves. Price being the primary concern, quality second and failure third. Chances are the rest of the consumable parts could have been replaced for another $5.00. If in doubt, replace it.

Enough on the replacement parts issue. What else attributes to reduced converter life? Cleanliness for one thing. Everything must be clean. The cleanliness standard for transmission fluid (Past Dex III) is around a 18/15 which in basic terms means nothing smaller than 18 micron will be found in the fluid. The human eye can detect particles of 4 micron or larger. The newer Ford SP type used in the 5R110 transmission and the New Dex VI found in 2006 and newer GM vehicles has an even higher cleanliness standard. How clean is clean enough? If you can see that nasty gray film that just doesn’t come off easily, try adding a little more caustic soda to your wash cycle. You must remove it, plain and simple.

Last we need to talk about surface finishes. Not just friction mating surfaces, we all know “the smoother the better.” For most part this applies to everything. Impeller hubs from the OEMs are mostly roller burnished to produce this mirror like finish, while increasing surface hardness. Also burnishing will help you hold exact OD dimensions while delivering a beautiful 4-5 micro finish. Burnishing bushings to size after they are installed assures a perfect fit every time. This process works on bronze and babbit-type bushings. Midwest Converters, Inc. burnishes outer sprag races for its new 52 element sprag for racing. This sprag holds a whopping 1600 ft. lbs. torque. This extra harden and polished finish is a necessary process to make the component live for thousands of friction free miles. This 52 element is a new design for the past 22 and 24 element sprag Midwest currently uses.

You do not have to purchase a new burnishing machine to do your own in-house roller burnishing. A used turret or engine lathe that you probably already have works just fine. You only need a 5hp motor to do the job. The secret for smooth mirror finishes is to use a burnishing oil of high quality such as SHELL GARCIA 405 or SPARTACUS 51112. The Shell product is good and easier to find; however, the Spartacus 51112 will give less chance of scarring (metal transfer) on steel due to the superior additive package. This stuff lasts forever without diluting into tramp oil. Five gallons will last a year.

Midwest Converters, Inc. in Rockford, Illinois, has been burnishing hubs and bushing with great success for 20+ years and would be glad to help you set up your plant for burnishing. See a couple of Midwest’s file photos for suggested tooling. They can help you there, too.

We have just shown you how to improve your converter closer to the OEM spec. So how close in tolerance is close enough? How clean is clean enough? At Midwest Converters “Good Enough isn’t Good Enough” and never will be. That’s why being a TCRA member is important to them. It helps them to be better. Look on the TCRA web site next month for a video link of this process. The rest is up to you. HAPPY REBUILDING!

Dennis Sneath
Midwest Converters, Inc.

– Found in January 2009 Newsletter