From park to reverse small bang in tranny.
 

hello on my 96 XJ6, when I go to start the car and then I sift from park into R I sometimes get a light bang or pop under the car. Sometimes it shifts smooth, and sometimes it pops. I notice that is pops more often when the car is on a slant rather than on flat surface. Is this normal, or does something maybe need to be changed?

Tranny jerk
 

It might be that your transmission fluid/ gearbox oil ( or whatever you call it) is a little low. Given that the problem is more pronounced when parked on a slope, whereby the fluid in the tranny runs to one end or the other of the box. On a flat surface there is a more even distribution of fluid. Check the fluid level and top up as necessary. There is a procedure, whereby you top up and run the stick back and forth through the gears, check the level again and repeat if needed, or something like that. Others on here may well know more.

Hope this helps.

Some occassional noise isn't unusual. There is intended free play in both the transmission output shaft and the differential. Sometimes you'll hear a noise when the free play is taken up.

Or....something indeed could be loose or broken....hard to say via the internet. A good visual inspection of suspension mounts, exhaust hangers, etc might reveal something.

Do you use the handbrake? It's best to set the handbrake first and then shift to "P". This way the weight of the car is held by the brake instead of the transmission. This is doubly important when parking on a slope. If you don't follow this practice already, give it a try and see if the noise goes away.

Cheers
DD