well when i drive my 1991 S5 i hear noise coming from under the car
it sound like a metal banging against another metal coming around the are of the transmission seems to me that its missing a rubber piece in between those to metals to prevent them from hitting. the transmissiont itself it good.
does anyone know what it is

 

Speedometer cable? Does your speedometer work? My cable broke and was smacking the bottom of the car, sounded really bad for a while then I realized what it was.

 

I don't think its the speedometer cable
its two metals and they make contact while driving and you could feel it when they hit

 

does your exhaust header have a shield around it maybe its loose and clangin around .

 

heat shields. look under the car and see if your catalytic converter and header have a metal shield around them. It could be rusted and dangling/loose.

the speedometer cable isnt anything to cause noise.

 

is it in the back of the car, if so look into the front diff mount.

 

yeah, check the differential mount... maybe take a peek at the exhaust hangers too just to make sure nothing is boucing around.

 

O..same as mine...1988 rx7 turbo.

after lost it....it lost the power steer when i use the brake on highway. but turn off the car and start again it's gone....

i put a aftermart metercable now..the power steer come back..so funny

 

I use to have a rattling noise from under my car.
I had the heat shield around the cat, which i took off and it helped with the rattling but occasionally i would hear it. I think it was the muffler, but now its gone.

 

is it when you accellerate or is it just randomly? my diff mount broke too and im putting off fixing it... i think im too lazy. is it hard to replace the front diff mount?