Gear ratio and towing
Thread Starter
JK Newbie
Joined: Jan 2023
Posts: 6
Likes: 1
From: St. petersburg, FL
Gear ratio and towing
There was no plate on the rear diff. Just stamps on the cover but nothing that gave a ratio.
I went to Mopar.com which I joined when I bought the Jeep and entered the VIN into the garage section.
Under my garage, standard tab, toweards the bottom on the right, it says "3.21 REAR AXLE RATIO".
In the user guide, page 105 and 106, for auto and ratio 3.21, it says MGTW 2,000lb. yet the 3.73 ratio is 3,500 lbs.
Why the difference ?
Worse mileage ?
More wear and tear on the gearing ?
New to towing etc. so I don't really understand the fine details.
I went to Mopar.com which I joined when I bought the Jeep and entered the VIN into the garage section.
Under my garage, standard tab, toweards the bottom on the right, it says "3.21 REAR AXLE RATIO".
In the user guide, page 105 and 106, for auto and ratio 3.21, it says MGTW 2,000lb. yet the 3.73 ratio is 3,500 lbs.
Why the difference ?
Worse mileage ?
More wear and tear on the gearing ?
New to towing etc. so I don't really understand the fine details.
Last edited by sunnyeveryday; Jan 25, 2023 at 08:12 AM. Reason: No sig with vehicle details
JK Jedi
Joined: Jun 2013
Posts: 11,362
Likes: 2,089
From: Willow Park, TX
Yes, the mechanical advantage of lower gearing (higher gear ratio number).
Are you the original owner of that jeep? Have you compared your RPMs to the gear charts to see if the factory gearing makes sense or if maybe that jeep had been regarded by a previous owner? You could also turn a tire by hand and count driveshaft revolutions as well.
Are you the original owner of that jeep? Have you compared your RPMs to the gear charts to see if the factory gearing makes sense or if maybe that jeep had been regarded by a previous owner? You could also turn a tire by hand and count driveshaft revolutions as well.
JK Jedi Master
Joined: Feb 2008
Posts: 12,907
Likes: 185
From: Maine
To add to resharp001's suggestion...
Put a chalk mark on the front drive shaft.
Put a chalk mark on one front tire.
Jack up the front tire with the chalk mark.
Rotate the tire two complete revolutions while counting the drive shaft revolutions.
The number of turns of the drive shaft will be the gear ratio.
3 and 1/4 turns will be 3.21
3 and 3/4 turns will be 3.73
A little over 4 turns will be 4.10
4 and 1/2 turns will be 4.56
A little over 4 and 3/4 turns will be 4.88
A little over 5 turns will be 5.13
A little over 5 and 1/4 turns will be 5.38
Put a chalk mark on the front drive shaft.
Put a chalk mark on one front tire.
Jack up the front tire with the chalk mark.
Rotate the tire two complete revolutions while counting the drive shaft revolutions.
The number of turns of the drive shaft will be the gear ratio.
3 and 1/4 turns will be 3.21
3 and 3/4 turns will be 3.73
A little over 4 turns will be 4.10
4 and 1/2 turns will be 4.56
A little over 4 and 3/4 turns will be 4.88
A little over 5 turns will be 5.13
A little over 5 and 1/4 turns will be 5.38
