Tonight when I went out to grab some groceries and dinner , I put the car in reverse to back into a parking spot I hear I loud "THUMP!" as soon as I shifted into "R" reverse from "D" drive. I did it a couple more times from "P" to "R" and "D" to "R" and I heard the same thump. It only happens when going into "R" and Sounds kind of like a grinding noise and can be heard clearly with the windows down. It is coming from the the back of the car. I've tried turning off the car and on and it still continued to happen. Until I drive home and onto my drive way and it did not make the same sound again. It's a 2006 IS250 with 157,000 miles. Never had any problems before like this. I have no clue to what the problem could be but I wanted to seek out for some help before I run into any problems. Any ideas on what this could be ? Thanks for any help In advance.

I have a sound that is similar to those who drive manuals, and shifting into gear, you'll hear a thumping sound.
I'm not sure if everyone has this... or if you're describing the sound that I have.

It's just one loud thump has a slight grinding noise to it as well, I'll try and get a sound clip if it happens again but for right now I'm clueless as to what it might be.

Its ok, it was just the neighbors dog.

I get the loud thump as well but usually only in the cold/mornings. By the time I get to work/leave work it won't make anymore sound.

Its either a bad mount or the trans is going bad.

Were you on a steep hill? I remember I was on a really steep driveway with my new TSX and when I shifted into R I heard a huge metallic thump but apparently it's normal. Never heard it since.

Hopefully it's not the Trans going bad. It drives smooth and has no problems. Hopefully it's just the bad mounts. I have been experiencing vibrations when I switch into reverse as well.

Nope I was never on any steep hill but I have heard about that happening to people parking on steep hills. But for the sound it sounds exactly like you described a huge metallic thump.

I back into my drive way every night when I park and have the same problem when I leave in the morning. I took it to the dealer a month ago and they took it for a drive and told me that it was normal because I reverse to park at home. Apparently it has something to do with the brakes engaging and disengaging the wheels but the technician said its nothing to worry about. Hope this helped