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
Looking up her butt
Texas Drive Train did the initial 3.91 install
SNL did a major overhaul at 70,000 miles
Jason and Steve align the rear cradle after Jason rebuilt the differential