I have a 1989 LeSabre Limited. My trans gives a bit of a kick when I put it in reverse. The fluid is up to the proper mark. Do you think it's time for a fluid and filter change? My Buick has 56 000 kms. BTW, there is no kick in any of the other gears. Sometimes, when I hold the brake pedal down hard.

if you suspect that the fluid and filter need changing, pull the dipstick and look at the colour of the fluid, it should be bright red.
Also the smell of the fluid makes a difference. If it smells burnt, rotten or otherwise horrible then its time to service your trans.

I would check the engine and tranny mounts also. Power brake the car in reverse and in drive and have someone watch the mounts to see if they move alot.