I've got a 91' Land Cruiser 4.0 straight 6, automatic transmission. When i get to about 40mph + it makes this weird like groaning or sounds like it's grinding almost but as soon as i let off the gas it's fine, and it only does it periodically. Also, when I'm in reverse and take my foot off the brake my car doesn't move at all. and when i give it gas to go it's bumpy and doesn't sound good at all. Yeah I know these are sketchy details but it's all I can think of right now blah. thanks for any help.