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  • SN95 4.6L Mustang Tech

Could someone explain the difference in gear sizes?

  • Thread starter Thread starter hersheyman
  • Start date Start date Jun 15, 2005

hersheyman

New Member
Jul 15, 2004
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Oklahoma
Jun 15, 2005
#1
  • Jun 15, 2005
  • #1
What does the size of a gear refer to? For instance, what does the size 3.73 equal. Is it a metric size of something? Is it the amount of grooves on the ring or pinion? Just curious where it comes from.
 
T

tjm73

Founding Member
Aug 3, 2000
2,418
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48
Rush, NY
Jun 15, 2005
#2
  • Jun 15, 2005
  • #2
It's not a size, it's a ratio.

Stock gears are 3.27:1 What that means is the pinion gear spins 3.27 times to turn the ring gear once.

3.73 means the pinion spins 3.73 times to spin the ring gear once. Teh higher (numerically) - to a point - the gear ratio is the faster the car can accelerate.

The ratio comes from a tooth coutn of the pinion gear and the ring gear.

Example: Say the pinion gear has 11 teeth and the ring gear has 43 teeth. 43 / 11 = 3.91
 

trinity_gt

10 Year Member
Jan 31, 2003
3,125
81
99
Canada
Jun 15, 2005
#3
  • Jun 15, 2005
  • #3
tjm73 said:
It's not a size, it's a ratio.

Stock gears are 3.27:1 What that means is the pinion gear spins 3.27 times to turn the ring gear once.

3.73 means the pinion spins 3.73 times to spin the ring gear once. Teh higher (numerically) - to a point - the gear ratio is the faster the car can accelerate.
Click to expand...

Yep. Compare the rate at which the car accelerates in 1st gear (3.38:1, meaning engine turns 3.38 times for every one turn of the transmission output shaft) versus 2nd gear (2.00:1). You won't go as fast in 1st but it offers more torque multiplication giving harder instantaneous acceleration.

Same thing applies to the rear axle where gear changes might go from 3.27:1 (3.27 turns of the driveshaft to one turn of an axle) to 4.30 or more. Higher torque multiplication at the expense of vehicle speed.
 

hersheyman

New Member
Jul 15, 2004
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0
Oklahoma
Jun 15, 2005
#4
  • Jun 15, 2005
  • #4
Thanks guys, that answers my question perfectly. I hate discussing something when I don't know all of the basics.
 
0

01SN8K

New Member
Jun 9, 2004
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Jun 16, 2005
#5
  • Jun 16, 2005
  • #5
the numbers such as a 3.73 or a 4.10 are the teeth on the ring gear divided by the pinion gears teeth.
 
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