I took her out yesterday and noticed that at 39 mph no problems but at the instant I hit 40mph the front end started to shake very badly. It also seemed like the front end would fall off but it stopped very quickly once the speed dropped below 40. I was using my kid and his GPS as the speedo is broken. I have replaced the kingpins but not tie rod ends but that should not make a difference. Could wheel balance be a issue? Were they ever balanced to begin with?? Does not seem a driveline issue (new u joints, flywheel put on correctly) since in lower gears but high RPM no shakes. rusty