R&P gears change nothing in throttle response. Throttle response is the time taken from the moment the throttle body is opened to the moment the engine responds, makes torque. Lower gears also don't move the powerband up or down, they just multiply the torque transmitted to the ground, to the tires. The torque number and torque-band applied to the r&p by the engine is the same no matter what gears you have. You will feel a bigger increase in power with lower gears, more acceleration, more pulling power while towing, throughout the whole powerband because of the multiplication of torque to the wheels. It takes a big increase in horsepower and torque to overcome the under-gearing over stock. I think with your setup gnarlly4x, it will pull about the same as stock maybe a little bit more in the lower end, less on the top end because of the characteristics of the cam, and the under-gearing vs torque increase will pretty much match stock performance with stock tires/gears from what I have seen in the past, I've enjoyed reading about your build and I'm anxious to hear your opinion on the outcome and dyno numbers.
Hello Gillesdetrail,
Interesting…
Scenario 1 - So, I should have just rebuilt my engine completely back to stock specs. Replace the 31” tires with stock 28” tires, leave the 4.10 R&P, and I would be happy at 80 MPH in 5th gear with my engine producing 143 lbs of torque at 3400 RPM?
Scenario 2 - Or… with my rebuilt engine, will I be a happy with my 31” tires, swap my stock 4.10 gears for 4.56 R&P to multiple torque to the ground, at 80 MPH in 5th gear with my engine producing 152 lbs of torque at 3400 RPM?
Scenario 3 - Or… with my rebuilt engine, will I be a happy with my 31” tires, stock 4.10 gears, at 80 MPH in 5th gear with my engine producing 152 lbs of torque at 3000 RPM, and 6 $100 bills in my pocket?
Scenario 4 - Now, I’m driving down the freeway at 80 MPH in 5th gear and I start pulling an uphill grade in my stock engine, stock tires, stock 4.10 gears with RPMs at 3400. The load on the engine increases, and I lose speed down to 60 MPH, now the engine RPM at 2500, my engine is producing 145 lbs of torque. I shift down to 4th gear to maintain 60 MPH. Now the RPM is up 3000, my stock engine is producing is 147 lbs. of torque.
Scenario 5 - Now, I’m driving down the freeway at 80 MPH in 5th gear and I start pulling the same uphill grade in my rebuilt engine, 31” tires, stock 4.10 gears with RPMs at 3000. At 3000 RPM my engine is producing 152 lbs of torque. The load on the engine increases, but in Scenario 4 it only took 147 lbs of torque to maintain 60 MPH, but I have 5 more lbs of torque, so I can easily maintain 60, and should be able maintain 70 MPH because at 70 MPH the engine RPM is at 2700, my engine is producing 148 lbs of torque. At 70 MPH and 148 lbs of torque, I don’t have to shift down to 4th gear to maintain 70 MPH.
Scenario 5 - Now, I’m driving down the freeway at 80 MPH in 5th gear and I start pulling the same uphill grade in my rebuilt engine back to stock specs, 28” tires, stock 4.10 gears with RPMs at 3400. At 3400 RPM my engine is producing 143 lbs of torque. The load on the engine increases, and I lose speed down to 60 MPH, now the engine RPM is at 2500, my engine is producing 145 lbs of torque. Since it takes 147 lbs of torque to maintain 60, I drop down to 4th gear and 3,000 where the engine is producing 147 lbs – just enough to maintain 60 MPH.
Is my thinking or my theoretical calculations incorrect?
"It takes a big increase in horsepower and torque to overcome the under-gearing over stock"... can you please explain in terms of laws of physics, mathematical calculations/formulas, or dyno test results.??
Thanks,
Gnarls.
