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Discussion Starter #1
Hi folks,

I have read so many great and helpful posts on this forum that I thought it was finally time to share one of my own challenges and hopefully find help.

I recently acquired a 1965 mustang convertible, sprint 200 6 cyl automatic. We loved it, researched the dealer and bought it. Although the exterior and interior are in awesome condition, it needed some mechanical TLC.

It had a definite shudder when it would get to ~65 mph. It was a vibration and was loud!!!! the first mechanic I took it to changed all the front end bushings, tie-rods, control arms etc.... this didn't help very much. and in a matter of days the car wouldn't work through the gears automatically, although they all worked individually (I don't think it is the original tranny)

The next shop pointed me to a transmission specialist and he found that the vacuum hose had melted. He also noted that the drive shaft (pinion) could be ~ 1" longer to better engage the differential ring gear. I had a new drive shaft made (they told me it didn't need to be balanced unless I was racing... I checked it and it was ~ 0.005" out of round). The longer drive shaft didn't solve the shudder/vibration problem, but there was a marked improvement.

The next garage, changed the tires (one rear was knotted) and the shudder/vibration improved more - it is now quite slight but ever present at ~65mph. Further at these speeds or when accelerating up hill, it quietly screams and sounds like ice-skates are being sharpened.

I have been reading the forum and I think that I understand this may be due to the pitch/angle of the drive shaft/pinion? Also may the 1" extension cause the gears to engage incorrectly?

I am really at a loss and not for driving my car from garage to garage - haven't really driven it otherwise. I need psyche-automotive help!?
 

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HELLO;

was the noise present before changes?

if not, which change created the noise?

the pinion angle will not cause any noise whatsoever in your case. if you jacked your car up 3 feet in the air you might get noise from the u joints binding.

can you post a video of the sound.

if it is a whine and only on acceleration, it is likely worn gears.
.
 

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I don't get the drive shaft issue. It's connected to the rear axle with a U joint and the sliding end is at the transmission tail shaft. If it's too short you would be having problems at the transmission end.

I would have the new one balanced. It's not a lot of money to have it done and it spins a lot faster then your tires do.

None of that has anything to do with the noise though. You should have the rear end serviced. Take the drive shaft out (again). Disassemble the input shaft and front assembly, remove the half shafts. Clean up all the internals and inspect to find out where the problem is. It's likely just a bearing, so replace all, along with the gasket and seals.
 

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You sure have gotten the run around. Lucky the car is getting better each time.

The front end work is questionable. Was the steering wheel shaking at speed?

What does "changed the tires (one rear was knotted)" mean? Did you buy new tires? Did they balance them? What is 'knotted'?

Worn rear end gears or bearings do not vibrate. They will howl and growl. Gears with the engine torque, bearings coasting.

These rear ends have a casting that holds the pinion (drive shaft) gear and ring (axle) gear in position. It would be almost impossible to screw this up like you are being told. It just would not go together.

You need to find someone from your local Mustang world and ask for some help. It always helps us if you post photos and video of any problems.

 

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Discussion Starter #5
Thanks for the reply. The vibration (which is much improved) is still present but only at ~65-70mph and increases it's frequency as I accelerate. It was always there from day 1 but the changes have reduced the amplitude of the vibration. The whine is not very loud at all. The last mechanic mentioned that this may be how it sounds. There is very little backlash (like none) in the drive shaft and the u-joints seem ok. The pinion/gear was inspected and thought to be in good shape. So the comments about bearings seem to be a good lead. I appreciate the feedback and will post video/pics when I return from travels. I did research a full rear end differential rebuild kit, but I am apprehensive about how difficult this might be. I have a sting mechanical aptitude, however I have never worked on a differential. Is this a relatively sophisticated procedure?
 

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hello;

the gears are diffiicult to set up.

sit in your car.

rev it to 1/4 throttle for 10 seconds and feel for vibrations.

rev to 1/2 throttle and do the same.

if it vibrates, the engine is likely out of balance.
 

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Thanks for the reply. The vibration (which is much improved) is still present but only at ~65-70mph and increases it's frequency as I accelerate. It was always there from day 1 but the changes have reduced the amplitude of the vibration. The whine is not very loud at all. The last mechanic mentioned that this may be how it sounds. There is very little backlash (like none) in the drive shaft and the u-joints seem ok. The pinion/gear was inspected and thought to be in good shape. So the comments about bearings seem to be a good lead. I appreciate the feedback and will post video/pics when I return from travels. I did research a full rear end differential rebuild kit, but I am apprehensive about how difficult this might be. I have a sting mechanical aptitude, however I have never worked on a differential. Is this a relatively sophisticated procedure?
To diagnose find a large area that is quiet and free of traffic. acc through 65 listen for the noise, at 75 let off the gas listen again. return to 65 and go into netural listen again. under power, coast, decel. is where the gears should make noise and each should be different. if the sound is the same for all modes it is likely axel bearings. the ford rear is the easiest to overhaul of all makes using die or some grease check the wipe of the pinion on the ring and shim to get perfection. preload all the bearings according to manual.
vibrations can be the wheels (bent), tires, drive line, flywheel, engine, dampener. all by balance. sorry but detective work is tedious. good hunting
 

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Axle bearings are pretty easy to check. With the wheels and brake drum off, undo 4 bolts holding the bearing retainer in. With a good yank, the axle should pop out. Then you can check the bearings. If they spin rather easily and for a while and make any sort of noise, they're bad. They should feel like they have grease in them.
 
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