My 4.10 gears have been great, only very slight whine. Did the break-in as documented (one extra 7 mile drive and then overnight cool down) and then next day began to stand on it. First at 19PSI (street setting) then at 29PSI) high boost. Two weeks later took it to the track and pounded out a 10.7 sec @ 131 MPH pass. Best time before the 4.10 gears was 11.4 @ 128!! This has been an awesome mod!