Vibration at high speed, Rear end?

[Numbles]

After my gear install a while ago there has been some terrible vibration coming from my 3.73's I think. Ever since the new trans and drive shaft the vibration has gone away some but the vibration is on and off. Sometimes there is none. And sometimes its noticable above 90.

I re-torqued the drive shaft bolts and 2 took about a half turn to what the chitlins manual specs. I think it was 90-95. Forgot. This seemed to help although I havent hit the highway since then. But I noticed some play in my driveshaft. Right at the u-joint. It can slide about a millimeter, maybe less. Back and forth between the clips. Anyone think that could cause my vibration as well. Remember this started after the 3.73's were put in. And since Im barely above 90 it doesn't cross my mind too often. The driveshaft is new though.

Could the rear tires also need a balance.


Dan.

 

[Mrgreen94gt]

Is the dogbone still on there?

 

[donkey_punch]

you need an aluminum drive shaft.

 

[mo_dingo]

If you have a dial indicator, re-check the backlash. Also get some prussian blue and check the wear pattern. This should give you an idea if the pinion depth is correct.

I am not sure what you mean by 1mm play in the driveshaft. Can you be a little more specific? Is one of your u-joints broken?

If there is "excess" play, then you need to find where the play is. i.e. hold one yoke steady, and turn the ds so you can see the play on that u-joint only.

U-joints are cheap, and easy to replace. If you suspect them as the culprit, or the u-joints are stock, then you should replace them.

Can you get access to a press? If you can then this project will be VERY cheap!!! If you can't, then you can attempt to do it on a bench vise. I did my brothers bronco on a vise. It wasn't fun though.
Scott

 

[JJ95GTID]

Your tires should be balanced if not already. Your bushings could be wearing out. Replace them. If you have original shocks and quad shocks they could be shot and need replacement. By what you wrote that it is only sometimes I would not think the gears are the problem. If the gears are setup wrong you feel/hear vibration all the time. A little play in the driveshaft is normal like you described while trying to turn it. It just sounds like your rear suspension is loose now since it has been up on a lift during the rear gear installation. Was it lifted using a frame type lift where the arms of the lift hoisted the car up by the subframe. If so, the suspension hangs by the control arms and may have damaged the original bushings. Just some thoughts.

 

[Numbles]

Every suspension part is stock with over 100k on it. Now that you mention it. This could very possibly be it. The shocks are probably done.

The play in the DS is the u-joint sliding back anf forth between the locking pins that hold everything together. Its a brand new Chrome moly DS. I plan on spraying out of the hole next spring and Just didn't trust the stocker or the aluminum one from ford.

 

[65StangBoy]

I am having very similar problems with my 95 GT. I have a very annoying vibration @ about 90 indicated. It's even more annoying because while its indicated 90, its only about 75 because of the gear change, making interstate drives a pain in the butt. I bought it used with 3.73's already installed. The previous owner attempted to fix the problem by having new U-Joints installed and having the driveshaft balanced. Overall I think he spent about $300, I wish he would have just bought an aluminum driveshaft. O well, hindsight is 20/20. I don't think its the driveshaft but I have a friend who has a '95 without the vibration so I'm gonna swap driveshafts real quick to test. His dad has been a Ford tech for the past 20 years so he looked at it too. They put it on a lift, removed the rear wheels and it still vibrated @ 90. It vibrates in 4th & 5th so its not anything with the transmission. The gears make absolutely NO noise so I don't think its anything related to the gear install. It has 132k miles on it with what I believe to be stock suspension. What do you think I should check first? Replace the rear control arm bushings or the quad shocks? Any help is appreciated.

 

[Numbles]

65stangboy, every switch driveshafts to find out. Coming back from the track last night reminded me of the vibration because it sucked. Let me know. Could it be the pinion angle.

 

[Meangene21]

Oh hell read my next post !! sorry

 

[Meangene21]

DAMN ! I didnt read your last post.

IF your play is in the driveshaft, then your pinion may not be shimed correctly OR you may not have replaced both the pinion bearing/raise and the raise that goes into the back of the axle. This would cause a NEW pinion not to tighten down all the way. Hopefully i described it correctly for ya.

I think Raise is the correct name for the piece that goes over the bearings.
(sorry i had a crash course and not sure of the terminology).

 

[Numbles]

Interesting info. Im going to have my mechanic check it out. Since he installed it maybe hell look into it for my. Hopefully 1105 will chime in. If I remember correctely he installed his gears himself. Maybe he could confirm a little more.