“What I Learned Today” With Jeff Smith: Converter Clearance

Converter Clearance

It’s very easy to not fully engage the torque converter into the front pump and input shaft splines on many automatic transmissions. The converter connects to both of these components and if the final connection is not made, the converter will be left too far forward on the input shaft. This will force the converter against the flexplate and serious damage may occur to both the engine and transmission if the installer tries to force this arrangement.

Here’s another check for when the transmission is already bolted to the engine – the free space between the flexplate converter pads and the converter. In this photo, there’s roughly ½- to ¾-inch which means the converter is fully seated in the transmission. If there is no clearance, the converter may not be fully seated in the transmission.

The standard procedure is to measure the amount of setback of the torque converter mounting flange to the bellhousing flange. A common number for most transmissions is slightly more than one inch but we’ve included a more accurate list in the accompanying chart for the more popular transmission applications.

Placing the converter on the input sounds easy, but we’ve occasionally struggled with this in the past. One TH400 fought us for almost 30 minutes and needed some minor persuasion with a soft mallet before it was finally completely seated.

If the converter is not fully engaged on the input and then forced onto the flexplate, this will press the engine crankshaft forward and very quickly destroy the crankshaft thrust bearing and also damage the transmission as well. This will require serious repairs to both engine and transmission, so it’s imperative that this converter setback from the bellhousing flange be verified before installing the trans to the engine.

Converter Chart

This chart lists the clearance from the converter mounting pads to the bellhousing flange measured with the transmission free from the engine unless otherwise specified.

Chrysler Torqueflite 727

1 ¼” from Bell Housing to Ring Gear

Chrysler Torqueflite 727 1 9/32” from Bell Housing to Pads
GM TH350 1 1/8″ from Bell Housing to Pads
GM  TH700R4/4L60E/2004R 1 1/8″ from Bell Housing to Pads
GM TH400

1-3/16″ from Bell Housing to Pads

GM Powerglide 1-1/8″ from Bell Housing to Pads
GM 4L80E 1-1/64″ from Bell Housing to Pads
GM 4L60ELS1 1-1/64″ from Bell Housing to Pads
Ford C-6/C-4 1-1/8″ from Bell Housing to Pads
Ford Case Filled C-4 27/32” from Bell Housing to Pads
Ford AODE

1-1/32″ from Bell Housing to Pads

Ford AOD 1″ from Bell Housing to Pads
Ford 5R55S 1” from Bell Housing to Motor Plate
Ford E4OD/4R100/5R110 29/32” from Bell Housing to Pads

About the author

Jeff Smith

Jeff Smith, a 35-year veteran of automotive journalism, comes to Power Automedia after serving as the senior technical editor at Car Craft magazine. An Iowa native, Smith served a variety of roles at Car Craft before moving to the senior editor role at Hot Rod and Chevy High Performance, and ultimately returning to Car Craft. An accomplished engine builder and technical expert, he will focus on the tech-heavy content that is the foundation of EngineLabs.
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