![OEM Dana Rear end](http://i512.photobucket.com/albums/t327/wrpnEthyl/Mods/Turbo%20Whistle/Drivetrain/Drivetrain22-640.jpg)
OEM Dana Rear End
The DANA OEM rear end in my GTO was a serviceable and reliable unit that held everything I threw at it for 90,000 miles. In fact, I have broken more on the Ford 9″ than I did on the DANA. The first major modification we made to the differential was adding a Harrop cover to it around 15,000 miles. This cover increased the capacity of the lubricant in the differential and I think contributed to the longer life. The Harrop cover also offered enhanced mounting that did help the wheel hop issues some but eventually I over drove it and just moved my wheel hop issues to another place in the rpm range. We changed the stock 3.46 gears for 3.91s at 22,000 miles. I purchased the Gears from Difftechnics in Austrailia along with a major overhaul kit and the LSD spring ennhancement kit. In my opinion the spring enhancement for the LSD was a hugely successful modification and contributed a lot to the long life of the OEM differential unit, especially the limited slip differential.
![Better shot of the Harrop Cover](http://i512.photobucket.com/albums/t327/wrpnEthyl/Mods/Turbo%20Whistle/Drivetrain/Drivetrain21-640.jpg)
Better shot of the Harrop Cover
![Looking up her butt](http://i512.photobucket.com/albums/t327/wrpnEthyl/Mods/Turbo%20Whistle/Drivetrain/SANY0050-1.jpg)
Looking up her butt
![Texas Drive Train did the initial 3.91 install](http://i512.photobucket.com/albums/t327/wrpnEthyl/Mods/Turbo%20Whistle/Drivetrain/PART951283198815399-1.jpg)
Texas Drive Train did the initial 3.91 install
![SNL did a major overhaul at 70,000 miles](http://i512.photobucket.com/albums/t327/wrpnEthyl/Mods/Turbo%20Whistle/Drivetrain/DSC03107.jpg)
SNL did a major overhaul at 70,000 miles
![Jason and Steve align the rear cradle after Jason rebuilt the differential](http://i512.photobucket.com/albums/t327/wrpnEthyl/Mods/Turbo%20Whistle/Drivetrain/DSC03115.jpg)
Jason and Steve align the rear cradle after Jason rebuilt the differential