91convertedstang

i have a 91 mustang lx that was originally a 4cyl auto and the guy before me converted it to a 5.0 H.O. standard and now has a horrible vibration around 55-58 mph, does anyone know what this is and how to fix it? it already shattered the first transmissions tailpiece housing...

9redfox3

Check the cross member on transmission check the u joints on drive shaft also check motor mounts?

enix187

check the balancer on the 5.0 crank too, if its bad there will be a piece of rubber jutting out of it, also what flywheel did you buy for the 5.0 (if its a manual)

91convertedstang

i had my buddy put the new/used trans i got in and the flywheel and clutch and everything were brand new on my motor so i sold the ones i bought with the new/used trans. the u joints are brand new and i purchased the heavy duty non greaseable. someone also told me being it was converted from 4 to 8 and auto to standard that the yoke might be a little too big for the tail shaft and that that could cause it too?? and when my buddy put the new/used trans in he tightened all the cross member mounts and rebolted everything all nice nice. and the balancer i already had checked out by 3 different garages, my last guess would only be the motor mounts so i will check those, thanks for the help

enix187

did you put a new trans mount in? also they're are bushings in the trans crosmemmber

91convertedstang

like i said the guy i bought it off had already converted it over and had a new cross member in place, all the bushings are fairly new with no dry rot or stress cracks. everything is bolted, i am gonna check the motor mounts but it is only felt in the shifter at that speed... if the mounts are tight i am gonna try to find a new shaft with new yoke and see if that helps

enix187

when you put the new yokes in the driveshaft you did put it back on in the same manner it came off? the driveshafts are balanced to the the rest of the drivetrain (at least thats what I'm told) If you don't bolt them up the same then it will cause a vibration in the drivetrain, if you wanted to check just unbolt the driveshaft and rotate it 90 degrees then go for a drive, it should either get better or worse, good news is you'l only have to do it three times at the most.

91convertedstang

i will give that a try this week on my day off, i have asked a lot of people and everyone keeps saying its the yoke bein too big for the tailshaft, but i have no play in the shaft at all. ill try rotating it to see if it is out of balance with the rest if that is true, thanks

91convertedstang

thanks for all your help guys, i actually figured out what it was on the highway on my way home today, my clutch is loose and throw out bearing is shot, doin 65 it started vibrating pretty good i pushed the clutch in a little and it stopped but my throw out is squeeling now so i am just replacing the clutch and everything

projectresto83

No it won't. I always read that but it is more of a just in case type of thing. Driveshafts are balanced off the vehicle so where it is bolted on the vehicle doesn't matter at all.