It’s a common phrase: There may have been a time when you worried about something, and someone who knew what you are going through said, “Hey, don’t sweat the small stuff.” Sometimes, this may be good advice. But other times, it may be wise to handle the small stuff before it becomes bigger “stuff.”
Fretting is something that starts small and ends big, like you can see in figures 1 (above) and 2 (below). In one recent instance, this caused a sudden no-move condition on a 2016 Chrysler 300 AWD with the 845RE transmission.
When this vehicle showed up at Transmission Pros, Sal noticed that when he put the transmission into gear, he could feel it engaged. Stepping into the throttle he could see the output speed sensor showing RPMs. As he revved it up, he heard a grinding noise between the transmission and transfer case. He pulled the transmission and separated the transfer case from the transmission, and voila: he found stripped splines caused by fretting.
The repair is obvious: a new transmission output shaft and a new transfer case input shaft; or, alternatively, a whole new transmission and transfer case. Either way, it is a very expensive fix for something that started so small. Fretting the small stuff by applying some dialectic grease on all AWD/4WD and axle splines as part of the everyday rebuild process preserves the workmanship involved, while giving the customer one thing less to sweat about.
Read more stories from our Technically Speaking column series here.
