98 frontier transmission swap

[CajunJay]

  I have a 98 2.4L frontier. I'm doing some performance work to the engine,  but I would like to put a 240sx 5speed in it.  I was wondering if anyone knows if it can be done, and if so...... where can I go to learn the steps.  I've been looking about. 

[datzenmike]

 

 

 

The only difference between the S13/14 and the D21 is the length. You would need to shorten the driveshaft. They are otherwise the same transmission and not worth the bother swapping.

 

 

[CajunJay]

Wouldn't it improve top end speed?

[ggzilla]

Both transmissions have the same 4th gear ratio: 1.00:1. Maximum top speed in achieved in 4th gear

[datzenmike]

1 hour ago, CajunJay said:

Wouldn't it improve top end speed?

 

5th is intended to just lower highway cruise speed RPMs slightly to perhaps gain a very slight mileage increase and lower engine noise. It was NEVER intended nor will it make a vehicle go faster. The limit to top speed is almost completely caused by drag or air resistance. Strange as it seems, it takes 8 times as much power to only double your speed. 

 

If your top speed in 4th is say 110 MPH @ 5,000 RPMs shifting to 5th which has a 0.759 ratio or 24.1% over drive, will drop the engine RPMs by 24.1% (1,200) down to 3795 RPMs. Now there is no way the engine will be making more power at under 4,000 in 5th than at 5,000 in 4th so the car will slow down till it reaches a lower speed where it can push through the air. 

 

To go 110 in 5th you would need to increase engine power at 3,795 to equal what it did make at 5,000 RPMs... and then you have merely equalled the speed not go faster. Remember drag? Air resistance increases proportionally to the cube of the velocity, increasing exponentially. Doubling the speed requires 8 times the power. To go just 10% faster or 121 MPH requires 33.1% more power.