Gearing FAQ
ATX RATIOS:
1st: 2.82
2nd: 1.50
3rd: 1.00
4th: 0.73
Final:
3.68 (Duratec, SPI?)
3.91 (Zetec)
4.15 (SPI? Contour)
(a junkyard, Performance Automatic, or Lentech should easily be able to supply you with the desired final drive ratio)
What this means on the strip:
The most important part of understanding how a car's transmission affects quarter mile times is to understand what RPM range is being used in each gear.
First, we'll calculate the RPM drop after each shift. This is simply the ratio of the gear you are changing to divided by the ratio of the gear you were in:
1/2 shift: 1.5/2.82=.52 This means that 2nd gear RPM will be at 52% of what the 1st gear RPM was at shift.
2/3 shift: 1.0/1.5=.66 3rd gear RPM will be 66% of what 2nd gear RPM was at shift
3/4 shift: .73/1.0=.73 4th gear RPM will be 73% of what 3rd gear RPM was at shift.
As always, the bigger the diff gear, the more torque your car has, and the faster you'll be in the quarter mile.
MTX-75 GEAR RATIOS:
1st: 3.67
2nd: 2.14
3rd: 1.45
4th: 1.03
5th: .77
Differential Gears:
3.42 (duratec)
3.82 (zetec)
4.10/4.11 (contour and FR)
What this means on the strip:
1/2 shift: 2.14/3.67= .60 60% of original RPM
2/3 shift: 1.45/2.14= .66 66% of pre-shift RPM
3/4 shift: 1.03/1.45= .71 71% of pre-shift RPM
4/5 shift: 0.77/1.03= .75 75% of pre-shift RPM
MT-285 GEAR RATIOS:
(because of the weirdness of the Getrag, we'll be using the combined ratios of the gears)
1st: 12.789
2nd: 7.793
3rd: 5.651
4th: 4.615
5th: 3.828
6th: 3.126
1/2 shift: .62
2/3 shift: .74
3/4 shift: .83
4/5 shift: .82
5/6 shift: .78
The final and most important installation will be how to use a dyno graph to determine the best shift points for your car based on the above data. This is particularly vital in an ATX car where your shift points can only be changed through reprogramming the ECU, either by chip or flashing. I will also cover selecting an aftermarket Torque Convertor for the ATX crowd.
I NEED YOUR HELP HERE: PLEASE POST 1 stock dyno of a zetec, a duratec, and an SVT each. PLEASE POST a full bolt on (no cam) Zetec and a full bolt on Duratec. PLEASE POST 1 dyno of a Zetec with either NEW GRIND crower 2s (NOT old), Cat 1s, or FR 2's. Thanks. It doesn't take me long to do these writeups, but I'd ratehr not search like mad for the dynos...
If you want to learn this stuff, I need your help
ATX RATIOS:
1st: 2.82
2nd: 1.50
3rd: 1.00
4th: 0.73
Final:
3.68 (Duratec, SPI?)
3.91 (Zetec)
4.15 (SPI? Contour)
(a junkyard, Performance Automatic, or Lentech should easily be able to supply you with the desired final drive ratio)
What this means on the strip:
The most important part of understanding how a car's transmission affects quarter mile times is to understand what RPM range is being used in each gear.
First, we'll calculate the RPM drop after each shift. This is simply the ratio of the gear you are changing to divided by the ratio of the gear you were in:
1/2 shift: 1.5/2.82=.52 This means that 2nd gear RPM will be at 52% of what the 1st gear RPM was at shift.
2/3 shift: 1.0/1.5=.66 3rd gear RPM will be 66% of what 2nd gear RPM was at shift
3/4 shift: .73/1.0=.73 4th gear RPM will be 73% of what 3rd gear RPM was at shift.
As always, the bigger the diff gear, the more torque your car has, and the faster you'll be in the quarter mile.
MTX-75 GEAR RATIOS:
1st: 3.67
2nd: 2.14
3rd: 1.45
4th: 1.03
5th: .77
Differential Gears:
3.42 (duratec)
3.82 (zetec)
4.10/4.11 (contour and FR)
What this means on the strip:
1/2 shift: 2.14/3.67= .60 60% of original RPM
2/3 shift: 1.45/2.14= .66 66% of pre-shift RPM
3/4 shift: 1.03/1.45= .71 71% of pre-shift RPM
4/5 shift: 0.77/1.03= .75 75% of pre-shift RPM
MT-285 GEAR RATIOS:
(because of the weirdness of the Getrag, we'll be using the combined ratios of the gears)
1st: 12.789
2nd: 7.793
3rd: 5.651
4th: 4.615
5th: 3.828
6th: 3.126
1/2 shift: .62
2/3 shift: .74
3/4 shift: .83
4/5 shift: .82
5/6 shift: .78
The final and most important installation will be how to use a dyno graph to determine the best shift points for your car based on the above data. This is particularly vital in an ATX car where your shift points can only be changed through reprogramming the ECU, either by chip or flashing. I will also cover selecting an aftermarket Torque Convertor for the ATX crowd.
I NEED YOUR HELP HERE: PLEASE POST 1 stock dyno of a zetec, a duratec, and an SVT each. PLEASE POST a full bolt on (no cam) Zetec and a full bolt on Duratec. PLEASE POST 1 dyno of a Zetec with either NEW GRIND crower 2s (NOT old), Cat 1s, or FR 2's. Thanks. It doesn't take me long to do these writeups, but I'd ratehr not search like mad for the dynos...
If you want to learn this stuff, I need your help
