grinding noise when in reverse

[sumyunggai]

i have 1991 240sx coupe with about 160,000 miles on the chassi. runs pretty well cept theres a grinding noise only when in reverse. if in neutral and rolling down the driveway it grinds. under gass it grinds. so pretty much whenever it moves in the reverse direction it grinds, at idle in reverse nothing happens out of the ordinary. haven't checked if this noise is present at higher speeds than 5 mph in reverse. oh and i think it has a factory lsd in there (found out by burnout test, two stripes on the ground). the grinding noise sounds similiar to my friends 96 240sx cept he has a aftermarket nismo 2way lsd and i don't. anyone have any ideas at why it does this?

*update*: i just read the "IMPORTANT INFO!! READ HERE BFORE POSTING!!!" and i found the handy little search button. seems like a bunch of people already posted my topic and got solutions. i'm going to go check some of those out. so no need to reply to this post.

Modified by sumyunggai at 8:33 AM 11/30/2005

**update** my dad and i took the rear brake caliper off and looked at it. turns out that one of the sliding pins that allow for the part shapped like a c which holds the brake pads pad to "float", as my dad put it, was rusted stuck. theres two big parts of the brake the heavy part containing the brake cylinder that pushes on the brake pads and a c shaped part that holds the brake pads themselves. More importantly my dad found out that the two bolts that hold this c shaped part to the brake cylinder assembly where MISSING! he said this was caused by the rusted sliding pin. since one of the sliding pins where locked they caused vibrations and the bolts holding the c shape part had nothing to push against. Both together created the chance for those loose bolts to vibrate right out of their proper places.

just thought i spread the word incase anyone else has this odd and unique problem.
Modified by sumyunggai at 9:59 PM 1/16/2006