<VV> Transmission or Differential

[Ted Firth]

I’ve got a 65 turbo Corsa 4sp convertible.  A couple of years ago I dropped
the engine and did some work such as new pilot bushing, clutch, u-joints,
differential rebuild, etc.  After all of the work was completed, the car
drove great.  However, after a few weeks of driving, I had a problem.  I was
driving to work and there was a thud in the back end which sounded and felt
like a fan belt breaking.  I pulled over to check and the belt was fine, so
I continued on my way.  When I arrived at work I started hearing what
sounded like a bad bearing with a pattern to the sound.  The car seemed to
drive just fine except for the sound.  

 

It is difficult to hear the noise in first gear, but it is there.  It is
loudest in 4th gear, especially when to let up on the gas.  When you’re
accelerating, the sound is almost non-existent.  It almost sounds like the
whine you here when you do engine braking except much louder.

 

With the engine off, I can coast down a hill and hear something that sounds
like either a bad bearing or gears not meshing.

 

Today, I put the car up on jack stands and tried to figure out if the sound
is coming from the transmission or differential.  With the engine off, I
turned one rear wheel at a time and couldn’t hear anything unusual.  So, I
started the car and put it in gear and tried to find where the sound was
coming from.  Unfortunately, I could not localize the sound.  The next thing
I tried was to stop one of the wheels while in gear.  I felt the wheel
jerking while it was trying to turn, which happened on both wheels.  My
expectation was there would be a smooth/even application of power to the
wheels.

 

Based on my observations, I think the differential is the problem.  

 

Has anyone else had an issue like this?  Am I on the right track?

 

Thanks,

 

Ted