Hello,

I have an '04 IS Automatic. Today, my uncle's neighbor helped me
change the differential fluid. The first change (using Amsoil 75W-90) was done @ 40K mi, and this time @ 75K mi (w/ Redline 75W-90).
Before I go on, the neighbor is a mechanic and is very mechanically knowledgeable.

* When he removed the drain plug, there was significant amount of metal
shavings (more than usual). My uncle's '03 IS300's differential fluid was
change just a few minutes before mine; and it had hardly any shavings. His
first change was the same time as mine, except he used Royal Purple 75-90
* We filled the diff w/ Redline; started the car and put it in D.
This is where the problem comes in.... Upon reving to get the old fluid to mix
w/ the new, there was a weird whining noise followed by a grinding noise. The mechanic standing outside also noticed that every time I applied the gas,
the wheel would hesitate and actually slow down before accelerating. He had never seen anything like this in all his years of working on cars.

Is this something I should worry about?

So after 1 mile of spinning w/o load on the vehicle, we drained the fluid and refilled. We noticed some metal shavings on the newly cleaned drain plug
even after the new fluid was put in the 1st time.

Is there something wrong w/ my differential?

Please advise.

Btw, once my car was done, we jacked the rear of my uncle's IS, and it made the same whining/hissing noise followed by wheel spin hesitation before accelerating. The main difference between his car and mine were 1) He hardly had any shavings fromt he 1st drain;and 2) in "D" w/o applying the gas, his wheels were spinning faster than mine ~ so it seems.

Thank you for your time.

J