Trailer Life Article about GCWR...etc.

Diff gear ratio change increases or decreases the torque multiplication
delivered to the drive axles

So going to a higher numeric (lower gear ratio) increases the torque
multiplication by the difference in ratio. Most all OEM's have their
available diff ratio options about 10% apart

Meaning that going from a 3.73 to a 4.1 will increase the torque multiplication
by about 10%.

So the why of a higher GCWR just by going to a higher numeric diff ratio...it has
MORE power delivered to the drive axles...so it CAN tow more and
still stay within the OEM's specifications

Ditto going down with a lower numeric, it will reduce the delivered
torque to the drive axles by about 10%

Can check the diff ratio on a used or any vehicle by :

• Roll the vehicle till one rear tire valve is pointed straight down
• Tape a length of string on the 'down' side of the drive shaft
• Roll the vehicle 'ONE' tire rev using the valve stem as the datum
• Count the number of full string turns on the drive shaft. That will be the first number of the diff ratio
• Fractions of a full turn is the second portion of the diff ratio
• Three full turns and 3/4's of a turn is a 3.73 diff ratio

Remove the string...gotta say that, as one fella got mad at me for not
saying that on another forum...and assume he didn't know better and it
wound itself up on him later one... :S


Again, amazing how so many don't understand the below stated early
on this thread...many threads and not just here, but other forums too...

BenK wrote:

First, IMHO, few truly understand the meaning of 'rating', 'limit',
'recommendation' from the OEMs. Not just automotive, but any OEM's
product ratings, limits, recommendations...