Torque Converter. Defining a. Quality Rebuilt

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1 Defining a Photo courtesy of Visual Cut-a-way Concepts The membership of ATRA is asking the Torque Converter Rebuilder s Association, as an industry trade group, to work toward developing measurable criteria. criteria. This This article article is the is the first first in a series in a series that that will discuss will dis- measurable cuss how we how can we better can better define define torque converter quality. What makes a rebuilt torque converter a quality unit? That s easy, you say: A quality rebuilt torque converter is one that works correctly when you install it and doesn t cause your customer to return to your transmission shop with a Quality Rebuilt Torque Converter problem. Okay, we can all agree on that. But how do you really define it? What measurable criteria can be used to determine if a converter is good or poor quality? TCRA believes that the first step in developing measurable criteria for the industry is to define some basic terminology. That way, with the benefit of all parties using a common language, issues can be analyzed and discussed intelligently. If torque converter rebuilders and transmission rebuilders don t at least start off with a basic understanding of a common glossary of terms, cooperation between the two Figure 1: Incorrect way to measure a torque converter by The Torque Converter Rebuilder s Association will just be that much more difficult. The two terms presented in this initial article are overall height and endplay. These are features of the torque converter that can be measured from the outside of the unit. As a transmission rebuilder, you don t have the ability to look inside every converter you use. Understanding the concepts and having the necessary tools to analyze these aspects of a converter can at least give you a fighting chance when trying to determine whether you have a quality unit. As you ll see in future articles, some concepts are easily defined, while some are elusive and, by their nature, difficult to pin down. Overall Height The overall height of a torque converter is a simple measurement, but there are things you have to pay attention to. The measurement is taken from the surface of the converter that sits flush against the flexplate (typically a pad or lug) to the leading edge of the impeller hub. Overall height (often referred to as stack height) isn t from the tip of the pilot to the tip of the hub (figure 1). 4 GEARS March 2005

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3 Defining a Quality Rebuilt Torque Converter With the drive hub on a flat surface, measuring the overall height of a torque converter can be done on a flat plate with a height gauge; not a carpenters tape measure on a warped bench. Height Gauge Figure 2 It s important to remember that, if you re measuring overall converter stack height, pilot length has no bearing on the overall height of the converter. On converters that use studs in lieu of pads to fasten to the flexplate (E4OD / 4R100 units, for example), you must measure from the base of the stud, not the tip of the stud. Additionally, a converter should be placed on a true, flat surface and measured with a precision height gauge (figure 2). Measurements taken on a dented steel bench with a construction tape measure won t provide valid data especially when you consider a converter that s out of spec by only a few thousandths of an inch can cause problems. And remember, correct overall converter height doesn t guarantee that you have the right converter. For example, remember the A4LD converters in the old Merkurs? The one with the short pilot? That converter had the same overall height as a regular A4LD converter. It s important to remember that, if you re measuring overall converter stack height, pilot length has no bearing on the overall height of the converter. That Merkur A4LD converter had the same spline count, stall speed rating, overall diameter, bolt circle diameter, pilot diameter, and overall height as a standard A4LD converter, but they weren t interchangeable, strictly because of the pilot length. How does a converter rebuilder know what the correct overall height should be? There are a number of charts that have floated around the industry for many years providing overall average heights. From experience we can tell you that some of these charts contain both correct and incorrect information. But without OEM drawings of each individual OE part number, it s difficult to determine the exact parameters and allowable range of each application. Generally, converter rebuilders get their overall height ranges from precision measurements of virgin cores. Having a good height spec on an E4OD converter is no big thing, even for a small one or two man torque converter rebuilding operation. Everybody sees plenty of those. But having a valid height spec on a late model oddball unit that someone has already cut open during a previous rebuild is a different story. 6 GEARS March 2005

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5 Defining a Quality Rebuilt Torque Converter Torque Converter Endplay Everyone knows, when you pick up a converter and shake it, components inside the unit rattle back and forth. Nobody panics when these parts shift back and forth, because we all know the torque converter must have internal clearance, or endplay. Elements in a torque converter need to rotate separately and freely from each other, and endplay gives them just enough room to do that. But how much is just enough? And how do you measure torque converter clearance correctly? How do you reliably set the clearance during the rebuild process? Do you need to set clutch (pack) clearance, as well as overall unit clearance, the same as you would in a transmission? The answers to these questions, as with seemingly all things automotive, depend on application. How Much Clearance is Correct? Some early AODE units came from Ford with as much as 0.050" overall endplay. The internal components you might replace in that AODE converter and the design of those components would dictate the amount of clearance you d set that same AODE to during a rebuild. We ve seen some late model Honda units have as little as 0.004". Anybody remember the old Mercedes fluid couplers with the extrasmall 1.100" diameter impeller hubs? It wasn t uncommon to find clearances of 0.150" or more in those units. As you can see, there s no onesize-fits-all number for proper internal clearance. And unlike measuring the overall height from a previously unrebuilt core, measuring the internal endplay from a virgin core won t always give you accurate OE design criteria, only because you don t know if the clearance measurement you get has been impacted by the failure of any internal thrust surfaces. If you re trying to get valid endplay clearance data from core measurement, first you need to measure for endplay, then cut the unit open and inspect for any damage or wear that could make your measurement invalid. This is not an accurate method for checking the internal clearance of a torque converter. How Do You Measure Torque Converter Clearance Correctly? Torque converter clearance can be measured in a variety of ways. Some methods are easier and more accurate than others. Reaching down into a converter with snap ring pliers and lifting components, for example, may tell you if a converter has internal clearance, but it isn t an accurate way to determine precisely how much clearance it has. There are several tools on the market today that will allow you to measure Figure 3: Torque Converter Endplay Gauge torque converter clearance accurately. Although it s at the higher end of the price scale, the quickest and easiest tool out there to adapt to a wide variety of applications seems to be the TCRS Endplay Gauge (figure 3). How Do You Reliably Set Torque Converter Clearance During Rebuild? In actuality, it doesn t really matter how you set it, as long as it comes out correct. Some rebuilders use removable shims, while others use sophisticated 8 GEARS March 2005

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7 Defining a Quality Rebuilt Torque Converter fixtures that not only align the components prior to and during the weld, but preset endplay as well. We only bring this up because there are advantages and disadvantages to both methods. Rebuilders who favor using a fixture to preset clearance will tell you that shims can be left in the unit, or can fracture and leave debris in the unit. Or they may suggest that the process of shim removal can damage internal components. Rebuilders who use removable shims will argue that presetting the endplay isn t precise enough, because of the variable nature of shrinkage that occurs during welding. As we ve already pointed out, it really doesn t matter how you set the clearance, as long as you get the proper results. Do You Need to Set Torque Converter Clutch Clearance Separately from Overall Unit Clearance? In a word, yes. However, how you set clutch clearance depends on all together now application. There are some late model Mercedes torque converters that have an actual multipledisc clutch pack, complete with pressure plate and snap ring. There are also late model ZF converters that have a captive clutch, where the damper and separate clutch plate are staked into place. Transmission rebuilders can relate to setting clearances in clutch packs that are designed like this; trans shops deal with clutch pack clearance on a routine basis. When rebuilding both of these types of units, you absolutely have to pay attention to clutch clearance separately from endplay clearance. But what about setting separate clutch clearance on units that don t have a captive clutch? On those units, setting overall endplay will accommodate clutch clearance as well. But a good converter rebuilder will still pay attention to the available travel of the clutch plate. Converter rebuilders often need to cut thin sections of material from either the clutch surface on the front cover, or from the clutch plate itself. Cutting excessive material from either of these Photos courtesy of Visual Cut-a-way Concepts surfaces can cause problems, caused by too much clutch clearance. Resulting symptoms are more prevalent in some applications than others. Additionally, some lockup converters maintain a thrust surface between the turbine hub and the front cover, while others don t. Ignoring the internal clearance of these components can build problems into units. The point of bringing all of this to light is that clutch clearance is a separate issue from overall clearance, and clutch clearance can t typically be measured from the outside of a finished torque converter. In conclusion, it s evident that considerable documentation, planning and control must be part of a good converter remanufacturing operation. And a good converter remanufacturer is always looking for ways to improve communications with you, the transmission rebuilder. If we all develop a better understanding of the terms and definitions used in converter production, we ll all benefit in the long run. Look for the next articles in this series for the presentation of such concepts as impeller hub diameter and finish, pilot diameter and condition, and torque converter runout. 10 GEARS March 2005

8 END PLAY GAUGE End Play Gauge Check your converter before you install it in the car! Whether you build torque converters or buy them from a distributor, this easy-to-use tool will indicate whether the clearances are correct. Save time and money before you make that final installation. It measures torque converter internal clearances, foreign and domestic, from the VW to the E40D to the V10 Dodge. Unit comes with tooling to test most torque converters. Unit can pay for itself with just one come back. Call for more information. EASY TO USE Place converter on fixture Set dial to 0 Press handle down Read the internal torque converter clearance TCRS is dedicated to keeping you on the leading edge of technology Dixon Street Des Moines, IA Phone: Fax: A member of the H E L C Group tcrs@helc.net Combining Experience, Quality, Innovation and Leadership