[Shop-talk] Axle ratio?

[Jim Franklin]

On Apr 12, 2015, at 3:46 PM, Dave Cavanaugh <cavanadd at frontier.com> wrote:

> I have a 2004 GMC Sierra extended cab, short bed.  I would like to find the
axle ratio and engine size.  I am pretty sure the engine is a 5.3 Vortec, but
I'm having trouble finding the axle ratio. None of the codes in the glove box
match anything I read on line.  Any pointers?  I will need to be towing a
trailer quite a bit in the future and need to know how heavy I can go.

If you can't read the tag on the rear end, you can do a quick and dirty
guesstimtae by counting the number of times the driveshaft turns to make one
revolution of the rear wheel (you'll need to keep one rear wheel from turning
if it isn't a limited slip). The more accurate way is to chalk the driveshaft
and rear wheel, then spin the driveshaft, and count the number of turns of
each until the chalk marks line up again, then divide the smaller number into
the larger. Helps to have a second set of eyes for the latter method.

The first should get you close enough to match to a published number like
3.23, 3.73, etc.