[eschaider]

How tall a rear gear you can run is a combination of how much low speed torque you have and how well mannered your engine is below 2000 rpm. If you have the torque and the engine manners, the tall gear will be a nice upgrade for you.

My engine has just under 600 ft/lbs of torque at the hit of the throttle even as low as 1500 rpm and it idles smoothly at 850 rpm. I run the M/T 295x65x15 ET Streets and a 2.73 ring and pinion. Even with that tall ring and pinion, I have to be cautious because a little exuberance in the driver's seat can easily light up the rear tires if the traction control is turned off.

Highway speeds are a whisker below 2000 rpm at 75 mph in fifth gear. I have the TKO600 RR gearset. How your car can / will behave is tightly coupled with the low speed torque you have available in the rpm range below 2000 rpm along with how well mannered your engine is at engine speeds less than 2000 rpm.

The more of a competition car type idle you have, the greater the risk the engine will begin to buck and cough if you pull it down below 2000 rpm in fourth or fifth gear. Be cautious, deliberate and circumspect if you decide to put tall gears in the rear end.

Also worth mentioning, don't overlook the impact tire diameter has on engine rpm. Should you decide on 30" diameter rear tires (295x65x15) you may have more or less massage work needed to fit them, depending on whose replica you have and where in that firm's production history your car falls.

Additionally if you do light up the tires with a tall R&P your driven wheel speed will increase stunningly faster than with a 3.73 R&P. The more rapid increase in wheel / tire speed with the tall R&P makes controlling the car more challenging — a bit of an understatement. If you use a modern engine management system, I would highly recommend implementing and using its traction control. You won't be sorry you did.


Ed