i need some help determineing what is causeing a bad viberation . wheel bearings are good, i checked rear axle bearings ..good.. i pulled chunk and carrier bearings are good. pinion bearings are good also. u joints are not new but appear to be in good shape. car has fmx tranny. stock torque converter.could the trans cause such a bad vibe , but shifts perfect , no slipping nothing as far as i can tell.i have been told the old ford drive shafts havea rubber liner inside and that it can get brittle and break off causeing an imbalance ????? the trans fluid is clear and doesnt smell burnt. it isnt tires im sure of that. this is definetely driveline but i cant pin point it. put tranny in park and rev motor there is a slight buzzing vibe to it so im not sure if it is the tranny or drive shaft or what.. any ideas would be very much appreciatted
the other thing is if the u-joint or third member has been changed, the wrong size bearing cap may be used in the yoke end of the drive shaft. check to make shure the diameter is correct for yoke.
check your crankshaft dampner, may have slipped, Have you checked engine timing? Also, double check firing order.
when does the vibraion occure? does it happen only on accelertion? or decellration? does it happen with the motor put in nutrual?
Did this just start happening? Did you spray undercoating on the driveshaft? The engine vibration in park is most likely the vibration damper going bad. The outer part will slip on the rubber sandwich, and become unbalanced. An easy way to tell this is to bring the #1 piston to the top of the cylinder and check the timing mark on the damper. It should be at 0° with the piston all the way up. The trans won't cause a vibration unless the torque converter is bad,and it would do it in park also. Take out your driveshaft and make sure your U-joints are free to move in all directions but with no play. They can freeze up,before they get play,and give you a VERY bad vibration. Jack up the rear of the car,remove the rims and tires. Put a lug nut on the brake drums(to hold them on)and run the car in drive to the speed the vibration occurred to eliminate the rims and tires from the equation. Iv'e had wet mud settle overnight on the bottom of a rim and it will be a shaker the next day! This is basically all I can think of right now. Good Luck with it! Someone here will hit on it!
. dampner appears ok, fireing order is correct ty for help it happens around 30 mph and continues all way to about 65 or 70 and slightly smooths out at higher speeds. same accelleration or deceleration, and still does it in neutreul as i said earlier u joints are not new but appear ok,havent disassembled them tho will check that also something i did levae out is car has sat up for almost a year.but engine and tranny are working fine unless it is the tranny with the vibe. ialmost think it may be the converter tho. other than changeing it any way to check that but what puzzles me is that car pulls hard , shifts great, everything but that vibe and it isvery very noticeable.
Does it have the same tires that it sat on for a year? If so your problem is flat spots on tires and the must be replaced. A vibration from 30 on up says to me tires, tires and if it's not that try some tires. A vibration from the driveshaft will occur(normally if it's not real bad) at higher speeds (starting around 50-55MPH and go away around 60-65MPH) from my experience.
This is why I said check dampner. Is this a buzzing or vibration? Tires as said, pull driveshaft and check by hand u-joints and check yoke where it slides in tranny for easy slide and no slop.
Vibration at 45 mph is frequently u-joints with stock gears. Another thing that can cause a vibe is the idler arm going bad. That will usually be at 45-50 mph too IIRC.
Sounds like what Bryant said, wrong u joint caps at the diff yoke and/or pinion angle. Thats my guess from your description. Mine developed a vibe this season and it was the wrong u joint caps. Joint was new and mint. Wrong caps though. I was skeptical but it fixed it going with the larger diam. caps. All 4 of my caps where the same size. I ended up using 2 u joints to make one correct one. My car has a large aluminum drive shaft. Fox body I was told.
. ty every one for replying, i did change tires and wheels before driving it after it had sat for year.it isnt like a flat spot or bump its a harmonic typ viberation will drive ya nuts (short drive for me lol ). ive checked everything i know and what all that has been suggested by you all, no luck , only thing i havent done is change the drive shaft out or pull tranny and check it and converter. anyways thank you all again , if any more suggestions im surely open to them . im mad at it now ..i wont stop till i find out what it is the vibe does feel stronger at the tranny tunnel.if that means anything
try a new trans mount or shim it up with some washers to see if it has and effect on the vibration. i have see this problem happen alot. these are easy tests to try and have very little cost.
All good suggestions. I am having the same issue. My car has a 250 and C4 tho. I feel it in the tunnel also, but not 100% sure. I am gonna try the tail shaft bushing next. Someone mentioned the angle and I am curious about that now since the shacles do seem saggy. .. I also had to do what Darren did and use two different U-joints to make one. That actually helped a little. I had decided to remove the joints to inspect them cause they had no grease fittings. They had no play also. One of the cups was full of dry and rusty bearings. That's when the delima began about finding out the cups were two sizes. I bought a U-joint and put it in. As I was installing it I noticed that it was not quite tightening up. The straps seemed to mash and just barely start touching the cups. That was with new straps also.
