Fretting Revisited - Transmission Digest

Fretting Revisited

Nonetheless, while conducting a seminar recently, an ATSG member who was there approached me with a manual transmission concern. The complaint he had with it was difficulty engaging the transmission from a standing start. It acted as if the clutch pedal was not fully releasing the pressure plate. Yet it seemed to shift through the gears OK once the vehicle was in motion. No work had yet been performed, and from all appearances, it seemed that the clutch pedal was functioning correctly.

Fretting Revisited

Shift Pointers

Author: Wayne Colonna
Subject Matter: Spline moving against spline
Issue: Proper lubrication

Shift Pointers

  • Author: Wayne Colonna
  • Subject Matter: Spline moving against spline
  • Issue: Proper lubrication

ATSG’s technical help line primarily concentrates on dealing with automatic transmission concerns. As a result, we very rarely take calls for manual transmission problems. Even ATSG’s seminars primarily focus on automatic transmission and drivability concerns.

Nonetheless, while conducting a seminar recently, an ATSG member who was there approached me with a manual transmission concern. The complaint he had with it was difficulty engaging the transmission from a standing start. It acted as if the clutch pedal was not fully releasing the pressure plate. Yet it seemed to shift through the gears OK once the vehicle was in motion. No work had yet been performed, and from all appearances, it seemed that the clutch pedal was functioning correctly. I suggested that the pressure plate may be defective or the clutch spline is sticking to the input shaft. He reported back to me later in the week to say that when they pulled the transmission out, it looked like the splines on the input shaft and clutch plate were rusted.

Once he said that I had a flashback. In March of 2013 I wrote an article about fretting. To my surprise I received more welcoming comments from this article than most others. In fact, I received a very informative booklet called:

“Fretting Corrosion in Rolling Bearings:
Cause and Avoidance” from INA Bearing Co.

I also received an email from Gary Croyle at Perfection Clutch. He is the director of product training there.

He sent me pictures as you can see in figures 1 and 2 explaining how fretting corrosion occurs in this environment as well. You can even see the actual corrosion deposits and not just the rust color. My thought of the clutch spline sticking to the input shaft was correct, but I honestly hadn’t thought of fretting corrosion being the cause.

It is good to remember when doing any work related to spline moving against spline, to give it proper lubrication to avoid the inevitable. Have you ever driven a vehicle that about 30 seconds after a stop you feel a little bump? As if it downshifted to first or someone gave you a slight tap in the rear? That would be the beginning signs of a drive shaft yoke spline to output shaft spline problem. Why worry when you can stop fretting?

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