Vibration driving me crazy!

fordguy

fordguy

Active LVC Member
Joined
Aug 7, 2012
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Location
Gray, TN
I just got done putting 4.10 gears in the Mark. They are broke in 500 miles I got a 93 driveshaft new joints and got the shaft balanced. All is good until I hit about 70mph when it starts to vibrate and gets worse the faster I go. Around 95 the car feels like it will vibrate itself apart. I have checked and matched output shaft and pinion angle. I done some searching and seen others not being able to get rid of vibe unless they get the 4" Dynotech but don't really want to spend that much on a driveshaft. So does anyone have any advice for me or a used dynotech shaft. I'm about to drive 25 hours to Houston and I think I will be crazy by the time I get there if I cant get this fixed. Thanks
 
same vibe on or off gas or brakes only thing that stops is getting under 70
 
Is it possible the shaft is bent or isn't fully/properly balanced? If it had anything to do with the gears/pinion I would assume you would be getting a pretty good gear whine (even before 70mph). Since you said it received new u-joints and accelerating/decelerating and braking have no effect on the vibration, the shaft is the only thing that comes to mind pertaining to vibrations at that speed. I'm sure someone with more experience/knowledge will chime in soon though.
 
It was doing it around 60 thats when I took it in to be balanced so it did improve but not 100% they checked the runout and it was straight
 
Try re-indexing the drive-shaft. Simply unbolt it from the Differential and rotate it a 1/4 turn and bolt it back up... Take it for a 100mph drive real quick and see if that solves it. If not, repeat again in the same rotation direction as before until the Vibe is gone

Also check the Differential bushings while you're under there.

I also just installed a new Diff with 3:73s and a 93 Drive Shaft, had the same issue as you, until I rotated my DS. Now its smooth til 115 (haven't gone faster than that in it yet)
 
well I indexed the driveshaft in all 8 holes in the diff and it got slightly better in 1 but still there. found a used dynotech driveshaft and think I might go that route.
 
Dynotech shaft fixed the problem. Smooth as glass till at least 120 :)
 
I am glad you found a repair method. My first experience with computer balancing was two guys, a lift, a roll of nickels and duct tape. Needless to say, I found the real thing fast.
 
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