"standard axle ratio"

[sooner]

I have an 85 scottsdale 1/2 ton w/700r4 and im trying to figure out my rear axle ratio. In the glove box it codes it as the GQ1 "standard rear axle ratio". I have dug around a bit, but cant really find a solid answer to my question. Can someone shed some light? Thanks!

[zieg85]

Could be whatever GM had excess of.  The only true way of knowing is to take the cover off and find what is stamped on the ring gear.  I would guess it is in the low 3's whatever it is.

[Lt.Del]

or count the teeth of the ring and divide by the pinion teeth, or something like that.  

[Irish_Alley]

Or post the numbers on your ring that can help or if you have a tac. and know your true truck speed GPS or something like that

[sooner]

Thanks for the replies guys.

I have a tach laying around, I guess that would be the easiest way to find out as posted above.

So I take it that they offered a bunch of different ratio's in these old trucks?

[Irish_Alley]

By time you done set the tach up you could of pop the cover but if you want to go that rout then
The formula for rear ratio is
If your running 50 mph @ 2k w/ 38" then
your ratio would be about 4.53
rpms x tire size / 336 / mph = ratio
2000 x   38    / 336 /  50    = 4.53
or just go here its one of those calculators
http://www.idavette.net/tech/ratioc.htm
The ratios can be 3.08, 3.42, 3.52, 3.73, 3.90, 4.11, 4.56, 4.88, 5.13, 5.38 might of missed a couple but I think I might have got them

[756man]

2.73 would be standard

[Irish_Alley]

can say it is or not but with something that is 25 years old and he not being the only owner you never know what has been swapped out

[Captkaos]

standard for the 2WD 10 bolts were 2.73, 4WD 3.08.
12 bolts were 3.08

[ohio hab]

My 1984 C-10 with an 700R4 had an 2.73 gear ratio, like other's have said if you don't think it is stock you have to pull the cover and count teeth.

[Stewart G Griffin]

Assuming it hasn't been swapped, i'd like to go out on a limb and say you got 2.56 until further notice.

1) The local dealership, if they're good, should be able to look it (what you got) on the computer with your vin#

2) If yer in a neurotic mood, you can read this long, drawn out thread i started almost 4 years ago concerning this very topic:
http://forum.73-87chevytrucks.com/smforum/index.php?topic=3785.msg17374#msg17374

[Grim 82]

Could be whatever GM had excess of.  The only true way of knowing is to take the cover off and find what is stamped on the ring gear.  I would guess it is in the low 3's whatever it is.

x2      It's the only definite way to know what you have. If I was a gambler I would put my money on 3.08

[VileZambonie]

85 C-10 should be 3.08:1 or 3.42:1

Don't bother trying to guess though, pop the 10 bolts off and remove the cover. The formula is simple and applies to all simple gear ratio's. Driven over Drive.

example

41
12
=3.42:1

[Stewart G Griffin]

2.56 or 2.73