Is there a way to measure how much backlash is in the differential assembly without removing it from the transaxle? The differential in our car appears to have excessive slack and it clunks nearly every time the transaxle is put in reverse (always when cold) and sometimes when put into drive.

 

The only way to check backlash would be to have the differential on a bench with both axles installed which would support the weight of the differential.

 

That's kinda what I thought, but in all honesty I was hoping for an easier method. How long can the vehicle be driven with the excessive lash?

 

Are you sure it's diff backlash or just gear engagement delay? When parking next time, place the car in neutral and allow it to roll into the parking spot if it is the opposite direction of how you would pull out. This will takeup the slack in the drivetrain, and when you place the car in gear next time you will be able to tell if the clunk is from excessive backlash or just a delayed/hard engagement of the transmission when cold.

The trans in my car has a bit of a hard engagement when cold. I've just blamed it on leak down of the hydraulic circuits from age. It just takes an additional moment to fully charge. You may also note that sometimes when the trans is placed in gear it feels like there are two engagements, the initial and then a slightly delayed thump. Welcome to the world of older automatics