Bad Vibrations! What could cause this?
When I got my car up and going after sitting for a long time I found that it had a vibration at about 35 mph and up. I figured it was the tires since they had been in rough shape and very old. Since I was ready to buy some new ones I figured that they new purchase would fix the vibrations.
So after the new rims and tires were installed I still had the vibration problem. Took the mustang back and they rebalanced the tires (see my other page on balancing tires) and I still had the problem. I had the vibration both in gear and in neutral, fast or slow. I put the rear end up on a jack and let the rims spin. Still had the vibration.
I narrowed things down to the drive shaft, or the universals, or the transmission. Hoping it wasn't the transmission I swapped out the universals with no luck. So I decided to have the drive shaft rebalanced. I found a local shop not far from my office and hauled my drive shaft in and put down in the counter. A old guy took one look at the drive shaft and says "Having vibration problems eh?". Shocked I said "Yeah, and I can't figure it out". His reply, "your drive shaft is toast". Turns out that these old drive shafts have a rubber insert in them and over time they, like everything else, gets old and rots out. This allowed the two pieces of the drive shaft to turn out of balance by about a 1/4 turn. So when the old timer looked at my drive shaft he could easily see that the ends where the universals are attached weren't lined up for perfect balance that I was having issues. I never knew that was important nor did I really know what to look for.
I didn't take a picture of the old drive shaft but if you have one, you can't miss it. There is a section in the shaft where the tube goes from a large diameter to a small diameter. The piece in the middle is a rubber bushing. So if it rots out you can easily twist or turn the drive shaft. This will throw it out of balance.
So after the new rims and tires were installed I still had the vibration problem. Took the mustang back and they rebalanced the tires (see my other page on balancing tires) and I still had the problem. I had the vibration both in gear and in neutral, fast or slow. I put the rear end up on a jack and let the rims spin. Still had the vibration.
I narrowed things down to the drive shaft, or the universals, or the transmission. Hoping it wasn't the transmission I swapped out the universals with no luck. So I decided to have the drive shaft rebalanced. I found a local shop not far from my office and hauled my drive shaft in and put down in the counter. A old guy took one look at the drive shaft and says "Having vibration problems eh?". Shocked I said "Yeah, and I can't figure it out". His reply, "your drive shaft is toast". Turns out that these old drive shafts have a rubber insert in them and over time they, like everything else, gets old and rots out. This allowed the two pieces of the drive shaft to turn out of balance by about a 1/4 turn. So when the old timer looked at my drive shaft he could easily see that the ends where the universals are attached weren't lined up for perfect balance that I was having issues. I never knew that was important nor did I really know what to look for.
I didn't take a picture of the old drive shaft but if you have one, you can't miss it. There is a section in the shaft where the tube goes from a large diameter to a small diameter. The piece in the middle is a rubber bushing. So if it rots out you can easily twist or turn the drive shaft. This will throw it out of balance.
Now, the good news is that I was able to have a new drive shaft made for under $200. It fit perfect and I haven't had any serious vibration problems since. The new drive shaft doesn't have that rubber bushing either so I won't have that problem in the future.