My brothers 1992 Ford Ranger 2.3 with the Mazda 5 speed manual has a vibration in 5th gear. He wanted me to ask the bitog crowd what could be causing that. I had him put it down in 4th and go 50-55 ish (same speed that vibration occurs in 5th) just to rule out that it's speed related, and no vibration in 4th. What could cause this? He also has a squeak sound that sounds like it's kn the drive line that only presents itself while on the throttle. I was going to try and video it but didn't have my phone on me. Tia.