New Converters: Visually Inspect, Measure, Document

Every torque converter shop should have a system to visually inspect, measure and document a converter when they are seeing the converter for the first time.

The visual inspection and measurements start on the outside of the converter and include documenting the physical make-up of the converter and any identifying markings. Completing a fill-in-the-blank check list is a quick and easy way of documenting your identification. The list should include converter diameter, pilot O.D. and length, bolt circle diameter, number and description of the mounting pads or studs, and overall converter height. For the impeller hub, record O.D., length, and description including step diameters, pump drive configuration and I.D. of the impeller hub bushing, if present.

The overall height is one of two measurements that must be checked before the converter is cut (Figure 1). The other measurement is the end-play (Figure 2).

The overall height and end-play measurements must be checked before the converter is cut, because there will be no way to reestablish these measurements once the cover and impeller are separated. All other measurements may be done anytime during the identification process.

Once the physical make-up of the converter has been documented, the identifying markings need to be noted and documented. Markings which are stamped or dot-peened into the surface will not be removed during the cleaning process, or made illegible during the painting process, so no further action needs to be taken. Paint dabs or ink markings may be removed or painted over, so special care must be taken to document and mark the locations of these markings. This is especially important for the markings used to index the converter to the flywheel for balancing purposes (Figure 3). These markings will need to be reproduced in a manner that will make them visible on a painted converter.

Visual inspection and measuring needs to continue inside the converter once the cover and impeller have been separated. The first thing that needs to be determined once the converter is cut is how the converter is built. Since the end-play measurement was checked before the converter was cut, you should already have a good idea off the converter stack-up. If the end-play measurement was in the .005" to .010" range, it is a good bet that the turbine hub contacts the cover and the clutch release clearance is adjusted separately. If the end-play measurement is more than .035", then the turbine hub probably does not touch the cover and the end-play is the clutch release clearance. You can verify the converter stack-up by doing a standard clutch release clearance check. Measure the distance from the clutch release stop on the piston to the cover, then subtract this measurement from the measurement from the front of turbine hub to the clutch stop position on the turbine hub. If the converter is built with the turbine hub touching the cover, the measurement will be a positive number; if the converter is built with the turbine hub not touching the cover (built off of the TCC clutch), the measurement will be a negative number. If the TCC clutch is a captive clutch, the clutch release clearance is also easy to check. With the retainer and piston attached to the cover, measure the distance from the top of the piston retainer to the top of the piston (Figure 4).

After the retainer and piston have been removed from the cover, compress the retainer down until it bottoms on the piston and repeat your measurement. The difference in the two measurements is the clutch release clearance. If the friction material is the correct OE thickness, your measurement will be spot on. If the friction material is worn, your measurement will be off by the amount that the friction material is worn.

The TCC friction material is the next thing to be inspected. Measure the I.D. and O.D. of the friction material and its thickness. Also identify the composition of the friction material. Since some converter models span many years and are used for many different applications, the friction material may vary. Allow space in your notebook for adding new models and document the make, model, years and engine of each model separately. This is also true for the damper assemblies for a given converter. Record the number of spring pockets, spring size (wire diameter) and configuration (single, inner/outer) for each damper assembly along with any identifying marks or numbers.

The stators may vary for different models of the same converter. Record any casting numbers along with the number of vanes (windows) and vane angles for each model. Since converters do evolve, you may want to add the piloting diameters and thicknesses of the adjoining bearings. If no bearings are present, identify the stator cap configuration. This is a good time to check the internal clearance. Refer to the article, "Internal Clearance", published in Transmission Digest, March 2009.

Impellers may vary from application to application within the same model of a converter. Impellers are easily identified by the differences in the row of dimples adjacent to the weld that joins the cover to the impeller. Viewing the impeller with the hub at the top, if the angle of the dimple leans to the right (as if you were giving a left handed salute) the impeller is generally accepted as a "high stall" configuration. If the dimple is standing straight up, the impeller is generally accepted as a "medium stall", and if the angle of the dimple leans to the left (saluting with your right hand), the impeller is generally accepted as a "low stall" impeller.

Different combinations of stators and impellers will yield different "K" factors. Record the stator and impeller for each different application.

It is now necessary to record whether the impeller overlaps the cover or vice versa. This information is necessary because impellers for GM 300mm units are now available in both configurations.

Visually inspect, measure, and document, document, document.

Ed Lee is a Sonnax Technical Specialist who writes on issues of interest to torque converter rebuilders. Sonnax supports the Torque Converter Rebuilders Association.