There is a strange clattering and knocking sound that happens after I shift gears to speed up on the highway. What do you think is causing this?
Have the drive shaft joints and rear axle pinion bearing checked to see if they have excessive play. Also, check to see if you have any broken motor or transmission mounts. This should help narrow down the problem for you.
If you need assistance with these checks, have a certified mechanic diagnose and fix the noise you’re experiencing with your gears.