I was driving my 90 si today with 160xxx miles on it and i came to a stop sign. As i put it in first and started pulling away i just stopped. The car runs fine but when i put it in gear it just makes a little grinding noise and the rpms and mphs go up? What the hell? The tranny was working fine other than a bad synchro in third up to this. There were no warnings signs or anything? What should i check first? thanks a lot