The Pony Car Project-New Gears

The pony car is really fun to drive and can accelerate well. Part of the reason for the great acceleration is the 4:10 gears in the differential. Someone changed the stock gears to this very low set. These work OK, but cruising at highway speeds has the engine turning at a higher speed than what is normal thereby decreasing gas mileage and increasing noise and vibration. Furthermore, I was concerned that the existing 4:10 gears were wearing as the pinion bearings seemed loose and there was some noise coming from that direction.

On Friday, I parked in front of a auto repair shop. One of the workers came out and told me that he had had a Mustang like mine only it was a 1988. He had rebuilt it including the motor. He showed me pictures and it did look nice. But it had been stolen. The insurance had paid him off and some of the parts had surfaced around the state. But as we talked, he said that he had a set of differential gears and the installation parts(shims, bearing, seals, etc).  He told me that the parts he had were brand new and still vacuum packed. He offered them to me at a really good price. I went home and checked parts stores and sure enough, he was offering me the parts for about $100 less then retail. The other cool thing was that these gears were 3.73 ratio which is what I wanted to change the Mustangs gears to anyway. The 3.73 ratio should give a good compromise of good acceleration and good highway cruising.

So Monday I called him and arranged to see the parts on Tuesday.  They were as he described, so I bought them. Overhauling the differential and changing the gearing is another project that I was hoping to do this winter.

 The install kit with bearings, shims and seals.

The ring and pinion gear set.