I recently did the u-joints on the driveshaft of my 2009 ford ranger. While doing it/while working on the diff side, I noticed that I can rotate the input shaft of the differential quite a few degrees back and forth before it engages.

Doing some reading shows that the diff should be adjusted to a few thousands of play, not the nearly 1/2" that I'm seeing.

Am I measuring at the right spot? Am I potentially feeling play somewhere else in the system, and if so is that play still acceptable?

It's been driving fine since the u-joint change, but I'm not sure if it should feel different given that this play has likely always been there.

  • The 'few thousands of play' that you have found described is likely the play between the input pinion and the crown gear. You may be feeling the play for all of the gears inside the differential. Do you see any movement on the output flanges when you rotate it these few degrees?
    – HandyHowie
    Jun 23, 2022 at 14:05
  • What do you mean by engages exactly?
    – GdD
    Jun 23, 2022 at 16:35

1 Answer 1


What you are describing as "play" is called "backlash" and is a characteristic of most gear drive systems.

In the case of a differential, there is a specific procedure for measuring and adjusting (usually via shims) the backlash to within a few thousandths of an inch. The procedure and specifications vary between vehicles but it's covered in the service manual.

In your case it's highly unlikely that you have disturbed the backlash in the differential and what you are feeling is just the normal amount of free play for the entire assembly. About the only time you need to check and adjust the backlash is when you have changed the gears. The backlash should not change over time on its own unless something severe happened such as running out of gear oil or contamination.

My guess is that what you're seeing is totally normal.

  • That's the word I was looking for - thank you! I wasn't concerned that I had affected the backlash, but that over time wear/something else caused the backlash to go way out of spec. The diff has 270,000km on it so it wouldn't be unlikely that wear has taken its toll Jun 23, 2022 at 17:16

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