Just bought an 88 1500 GW with 20,000 miles with what was called an engine knock after warmed up. I drove the pants off of her for 10 miles starting and stoping bringing her up to temp. ,nothing, ran nice , no knock. Paid for her and drove her home 35 mins. on the freeway at 75 mph, nothing. After riding around town the knocking and rattling begins. I got a good deal on her and am prepared to bite the bullet to repair her. Any idea what I may be dealing with here. If i keep her under 3000rpm it's better . The sounds seems to be comming from directly under the tuperware gas tank facade. Any suggestions or remarks will be appreciated! Thanks, Jeff