Originally Posted by crrowley12
This is going to be a dumb question, but I am new to muscle cars. Does anyone care to explain what is meant by the 2.65 vs 3.06? How do you know what you have, and how would you go about changing it if you wanted?
It refers to the gearing in the final drive (differential).
For each 2.65 rotations in the driveshaft there's 1 rotation at the wheel.
A 3.06 would increase the gearing ~ 15.5%. This would give some faster acceleration rate, with some decrease in fuel economy.
It would be similar to going from 5th gear (.83:1) to 4th gear (1:1) with the 5 speed automatic.
Or being on a 10-speed bike - lower gears allow you to climb hills and grades with less effort expended. At downhill or level conditions, you shift up to to higher (numerically lower gear).
Its not cheap to change ring and pinion gears after the fact, as there are clearances (lash and pre-load) that must be set precisely to avoid gear noise and wear. Plus the cost of the near R&P gear sets.
The $100 option from the factory is about the starting price for a R&P set alonge would run (probably more like $175-185), then the labor to have a driveline shop set up the new R&P gears...
Another way is to swap the center section (aka 'pumpkin') if a good used one can be found and its a bolt-in operation. Not sure if the 215mm (3.06) uses different axles/half-shaft from the 198mm (2.65) unit or not...
Most of the V8 automatic cars (300, Magnum, Chargers) may have
the 215mm 3.06 rear ends, but there were a few out there with the other 198mm with the 2.65, 2.54 gearing. There's likely the ID label on these units that indicate the gearing they're equipped with.