Hey folks,
First time rebuilding my rear differential (Chrysler 9.25) what’s this contact pattern trying to tell me?

 

It's telling you there is something wrong ... The FSM here has pictures of various contact patterns. Looks like both pinion depth and backlash are a little off but I'm an amateur at it too.

 

What is your backlash set at? and it looks like you pinion depth may need to add a shim. Backlash should be 0.008 to 0.006. I set them up at 0.004.

 

.006 was my backlash. I set it up via the service manual. Got my 4 readings initially with variance not greater then .003 between them. Picked the lowest area of backlash and made all future readings from the same tooth. Torques down cap bolts and preload cups then rechecked. It was sitting right at .005 to .006 on for different spots. I tried holding the gear as I spun the yoke to get some kind of load on it.

 

It sounds silly to me but im having trouble figuring out what contact pattern it relates to in the service manual. anyone have any ideas?

 

There should be a diagram showing different patterns and what to correct. For example if the pattern isn't centered it means the pinion needs either more or less shims