I noticed that my car has what it seems to be significant differential play. I have a 1993 Acura Integra with automatic transmission. What I mean by play is simple: say I jack up only one front wheel and leave the other one on the ground. Then I can turn the wheel that is in the air probably close to 20 degrees without significant resistance. There is no noticeable backlash between the wheel and the axle and also no bearing noise. I can also replicate this by going under the car and turning the axle by hand, with identical results. I am guessing this backlash is coming from the differential, but I really don't know enough about the inside of automatic transmissions to be confident.
My question is twofold: what amount of backlash is normal in an automatic transmission/differential and at what point should I get worried? Second, what are the most likely reasons for too much backlash and are there any (relatively) easy things to try and fix it before opening the transmission up for an overhaul?
I should mention that all the above applies when the transmission is in park. The other symptoms that might be related and make me worry that this is excessive play are a slight clunk when changing into drive/reverse and also a slight readjustment (sliding forward or backward) after putting the car in park, shutting the engine and releasing the brakes.