matty

iTrader: (54)

Went out on Rt 287 last night and got to about 70 not to fast in 5th and i was taching like about 3000...i went back home and took out my friends auto 3rd generation and got out on the highway again and taching alot less at 70-80...is this a common thing between auto and manual...and if so, WHY ?? ive always wondered why this is ?

Kevin Wong

Manuals
1st 3.285
2nd 1.850
3rd 1.206
4th 0.954
5th 0.759
final 3.823

Autos
1st 2.785
2nd 1.545
3rd 1.000
4th 0.694
final 3.789

As you can see, the 4th gear on the Auto is shorter than the 5th gear on the manual. The final drive ratio is also shorter on the Auto than is on the manual. This is why the manuals rev higher at any given speed. However, manuals will receive much more horsepower and torque at any given speed. When I first looked at the ratios, I thought Nissan should have given the manuals a 6th gear with a ratio of .6 This would give a little better fuel economy and a quieter noise level inside the cabin, but would probably increase the cost of production (ironically the economical Sentra will be getting a 6-speed).

I think we've all noticed that 4th gear and 5th gear are basically the same on the manuals, there's only a .195 ratio difference. I think when designing the transmission, the ideal speed limit was 55 MPH. The auto would be underpowered and the manuals would be just right. However, since then the speed limits have been pushed back up to 65 and people on the average drive at 70 MPH. I think Nissan should redesign their transmission ratios. Although the car gets pretty darn good fuel economy, I think they can do better.