Drivetrain Vibration From The Rear End In 5th Gear

Discussion in 'Fox 5.0 Mustang Tech' started by GoldenEagle91, Apr 2, 2014.

  1. Hi guys,

    When driving my car on the highway and I put it into 5th gear, if I am not going faster than 65 I get a nasty vibration from the rear end as though its hopping around. If anyone has any idea as to why this is happening please drop me a line. I know this vibration is really bad for everything in the drivetrain and I want to get this squared away in the very near future.

    MikeH686 likes this.
  2. Is it rpm or speed dependent?
  3. Its RPM dependent. If I'm not revving at at least 1500 it shakes.
  4. I would start by checking the u joints
  5. Okay. If U joints are worn out will that give it enough play where it could get that vibration like i think you're saying?
  6. hellz yeah
  7. Okay man, thanks for the heads up.
  8. If it is RPM dependent can you duplicate it while stopped with the clutch in if you slowly raise the rpms? If it is speed dependent and it only does it at a certain speed, then if it IS doing it does it go away when you push the clutch in? If it is RPM dependent does it do it in 4th gear or 3rd gear at 1500 RPM? See what I'm doing here? Does it do it at 65 mph ALWAYS or only in 5th gear. How bout 65 in 4th or 65 clutch pushed in?
  9. that'll help determine if its in the driveline or wheels/tires
  10. Good points, I will try this tomorrow when I'm driving it on the highway. The other thing it seems is if I'm trying to ease into the gas if I've dropped below 65 it'll sometimes start doing it. Say for instance I'm in 5th and I'm coming up to an incline and there is more of a load it will start shaking if I don't down shift into 4th.
  11. That sounds like a spark miss under load.
  12. So you'd recommend changing plugs?
  13. Not what I said lol. It could be a cracked plug yes. My money is on a bad wire. Burned or corroded inside the end at the plug or cap. Just speculation here but I'd start looking at wires. A spark miss is the most likely miss to occur under load. Plugs don't usually crack for no reason. And wires fail easily. I'd start there.
  14. Haha I know that's not what you said but I was asking. I will check the wires today and see if they're shot.
  15. To update yall, I checked the wires and there was a wire that had some of the rubber coating around it worn through so im going to assume that that is where the misfire under load could be coming from that you described. Also, I filled up with some premium because I believed that I might have been experiencing some spark knock but I'm not sure because I don't know what I am listening for. It seemed to have gotten rid of the noise that I was hearing so I'm assuming it needs premium or that I need to retard the timing a tad.
  16. If it was fine and then had a problem leave the timing alone. It didn't just change overnight. Put wires on it and see what ya get.
  17. Okay, I will give it a try. Thank you for your input!
    gearheadboy likes this.
  18. I was driving home from work today after having 93 octane in the tank and the shake only occurred when I put my foot more into the throttle. I believe that it is in all likelihood the misfire that you were talking about because the engine can not burn all the fuel that is being pumped in due to the worn spark plug wire. New wires coming Saturday.