any one now about ratio or gears

December 04, 2004, 09:34:48 PM

what does it mean when people have 4.30gears does that make a big difference in the car and wha is it for

Re: any one now about ratio or gears

Reply #1 – December 04, 2004, 10:03:44 PM

The gear ratio is essentially how many times the driveshaft turns in order for the wheel to turn once. For a 4.30 gear, the driveshaft turns 4.3 times for every revoltion of the back wheels.

The gear ratio affects torque multiplication, engine wear, top speed and fuel economy. The higher the number the higher the torque multiplication, but it also results in more engine wear (the engine has to turn more revolutions per mile travelled), lower top speed (the engine will redline sooner) and lower fuel economy (because the engine is spinning faster it will burn more fuel).

The car will take off quicker with higher gears because the engine revs up more quickly, but it also hits its redline more quickly, resulting in a lower top speed.

4.30 gears is too much for a stock T-Bird or Cougar (and likely would not be available for a stock 7.5" rear end). You'd fly off the line but you'd very quickly run out of power as the engine struggles to breathe at high RPM's. 3.73's or 3.55's would be better choices. Bear in mind that if you do a lot of highway driving the 3.73's will result in a considerably higher cruising RPM. Stock, your gears would be 3.27 (some V6 cars), 3.08 or 2.73. Turbo Coupes had 3.55 (83-86 models and 87-88 with 5-speed tranny) or 3.73 (87-88 automatic models). The 87-88 models had an 8.8" rear, so gears from one will not fit your stock 7.5" housing.