How do you "check" gear ratios
Thread Starter
JK Newbie
Joined: Aug 2010
Posts: 66
Likes: 0
From: Fayetteville, AR
How do you "check" gear ratios
I have had a few people post and tell me that my jeep is acting strange because it might have different ratio in the used d30 I just had installed. How do I "check" to make sure it is 3.73 like the original?
JK Jedi Master
Joined: Feb 2008
Posts: 12,904
Likes: 185
From: Maine
Chock both right side tires.
Put the transmission in neutral, transfer case in 2wd.
Jack both left side tires off the ground, support with jack stands.
Put a chalk mark on each drive shaft, lined up together.
Spin the front tire (by hand) 2 revolutions. Count the front drive shaft turns.
Spin the rear tire (by hand) 2 revolutions. Count the drive shaft turns.
They should have turned the same number of turns, and the chalk marks should have stopped in the same locations.
The number of drive shaft turns will also be the gear ratio.
Put the transmission in neutral, transfer case in 2wd.
Jack both left side tires off the ground, support with jack stands.
Put a chalk mark on each drive shaft, lined up together.
Spin the front tire (by hand) 2 revolutions. Count the front drive shaft turns.
Spin the rear tire (by hand) 2 revolutions. Count the drive shaft turns.
They should have turned the same number of turns, and the chalk marks should have stopped in the same locations.
The number of drive shaft turns will also be the gear ratio.
Last edited by ronjenx; Apr 15, 2011 at 07:28 PM.
Thread Starter
JK Newbie
Joined: Aug 2010
Posts: 66
Likes: 0
From: Fayetteville, AR
Chock both right side tires.
Put the transmission in neutral, transfer case in 2wd.
Jack both left side tires off the ground, support with jack stands.
Put a chalk mark on each drive shaft, lined up together.
Spin the front tire (by hand) 2 revolutions. Count the front drive shaft turns.
Spin the rear tire (by hand) 2 revolutions. Count the drive shaft turns.
They should have turned the same number of turns, and the chalk marks should have stopped in the same locations.
The number of drive shaft turns will also be the gear ratio.
Put the transmission in neutral, transfer case in 2wd.
Jack both left side tires off the ground, support with jack stands.
Put a chalk mark on each drive shaft, lined up together.
Spin the front tire (by hand) 2 revolutions. Count the front drive shaft turns.
Spin the rear tire (by hand) 2 revolutions. Count the drive shaft turns.
They should have turned the same number of turns, and the chalk marks should have stopped in the same locations.
The number of drive shaft turns will also be the gear ratio.
Holy cow!! You are right. 3.75 times around on the back and over 4 on the front. Why would the mechanic not know this. You are the man ronjenx!