I took the car out on the highway last weekend for a speed test. Discovered it started vibrating after 60 mph and was so bad at 70 that I was afraid something would blow. Vibration was somewhere under the car; I could feel it in my seat. Seemed the floor was vibrating; nothing on the steering wheel. I suspect the drive shaft. DS is the original; everything else has either been replaced or rebuilt, as follows:
Diff rebuilt,
Wheel bearings replaced
Transmission replaced with rebuilt used
Flex plate replaced with good used
TQ converter replaced
New tires, supposedly properly balanced
Vibration only occurs when driving, and only first noticeable at 60 mph; perfectly fine in Neutral at all RPMs.
I’m thinking of first remounting the drive shaft 180* from where it’s at now (since everything was removed for the restoration and most likely the DS isn’t where it was before we started).
So my question; at which end do I reposition it? Diff or tranny?
And if I pull the DS out of the tranny, will I lose fluid?
Make sure the driveshaft is not too short. if it is it will wobble in the trans tailshaft ! I had the same symptom and it was because the rear Diff yoke had been changed to a shorter one, thereby causing the diveshaft to be pulled back to where the front of the driveshaft wobbled in the trans tailshaft.
I was lucky in that I had gotton the original 4.30 pumpkin with the car when I bought it so I just measured the yoke on 3.50 pumpkin that the PO had had installed at a shop mind you and the one on the 4.30 and found the yoke on the 3.50 to be quite a bit shorter. If you know someone with a simular drive train to yours, you could measure all the related parts. Maybe somebody can add to this …
Check for slop in the tail shaft bushing in the transmission. This is the bushing that supports the drive shaft. If you lift the car at the rear (put jack stands under the rear axle) you should get only a tiny amount of fluid coming out unless the transmission is over filled.
Bill, I think you hit it. I’ve also got a small fluid leak at the output shaft seal. Seal has been replaced twice, and still leaks. Likely a worn bushing. I’ll take it back to my tranny guy and have him replace that first.
When I finally got my car on the road after buying it, mine had a shake at 40MPH and up.
It ended up being that whoever put the U-joints in the drive shaft last didn’t center them, so while all of the snap rings were there, one of them wasn’t in its groove. That meant the shaft wasn’t aligned along its full length.
I changed all the U joints at the same time and found that one of the rings wanted to do the same thing, almost like the cups were too big for the yolk.
While holding the drive shaft up off the blocks I was using to press, I hit the yolks on each side with a dead blow hammer and that centered it all up and all the rings dropped into their grooves, no problem. Then I smacked it again with the deadblow and they moved a lot more freely.
When I first bought my car I had a vibration as well, but it was more of a balance vibration because it had a rythem (sp) after changing the u joints, balancing the tires, checking bearings it was still there, it did not go away until I swapped the auto to a manual, same drive shaft so it muct have come from the tranny or torque converter…
Hopefully you didn’t use a TCI torque converter. We just had to change the one in my father’s 66 Mustang because we had a severe vibration around 1800 RPM after converting from 4 spd to a C4 setup. I pulled my hair out trying to figure what it could be. All the Mustang forums were complaining about TCI TQs being out of balance POSs so I sent the TQ out to be checked. It was “way out”. The new one (not TCI) works great.
Solved my vibration problem … the drive shaft was out of balance. When I took it in for re-balancing, it had 2 factory weights. When I got it out after balancing, both weights were gone and 1 small washer was welded at one end. Car seems to run smooth now up to 70 mph. I’ll take it out one of these days and see if I can get it faster than that; just hope I don’t attract the attention I used to get 40 years ago!!
Also had the tail shaft bushing replaced; original was babbit, new is bronze. Tranny shop guy said bronze hold up better.
From Wikipedia …“Babbitt, also called Babbitt metal or bearing metal, is any of several alloys used for the bearing surface in a plain bearing.”
Read more here: http://en.wikipedia.org/wiki/Babbitt_(metal)
