how to find out what gears are in a rear end??

[police1]

this might be a stupid question but how do i figure out what gears are in a rear end by turning the yolk??

[Long Island RT]

How many times do have to turn the yolk to get the wheel to go around once? - that would be it.

With a suregrip - you can do it with both wheels off the ground.  Without one - one wheel should be on the ground or held not to move.

[nvrbdn]

 

[John_Kunkel]

Without limited slip (Sure-Grip) the ratio can't be read directly from yoke revolutions, the spider gears are a 2-1 ratio.

To check the ratio with limit slip jack both wheels clear of the ground and turn a tire one revolution while counting the driveshaft turns, the number of driveshaft turns is the axle ratio.

Without limited slip jack only one tire clear of the ground and turn the tire two revolutions while counting the driveshaft turns.

[Long Island RT]

hmmmm... 

So... if you do a burnout with out a limited slip rear - the tire that's spinning is going 2x as fast as your speedo would read?

[John_Kunkel]

No, the spider gears are 2-1 reduction gears. If the rear end has 3.55 gears and you turn the yoke 3 1/2 turns with one axle immobilized the axle that is free to turn will turn only two turns. Same for any other gear ratio.

[Long Island RT]

OK - maybe I'm not the brightest bulb in the package....

3.55 gear ratio
yolk turns 3.55 times
one tire doesn't spin at all
the other tire spins 2X?

[green69rt]

If you look carefully at the rear end there is usually a metal tab hanging off of one of the rear end bolts.  It will have the rear end ratio.  If that is missing you have to use the turn/ratio method.

[RD]

jack up the rear end...  turn the wheel twice and count the total rotations of the yoke.  # turns:1 = your gear ratio

[John_Kunkel]

OK - maybe I'm not the brightest bulb in the package....

3.55 gear ratio
yolk (sic) turns 3.55 times
one tire doesn't spin at all
the other tire spins 2X?

Yep.

[lighting74]

agree with green 69rt there is a metal tag on the bottom usually behind one of the nuts on the bottom that will say like 2.76 or 3.23 ? giving u your gear ratio maybe have to brush the dirt and grease off to find it

[charger2fast4u]

So on a posi rear you would jack both rear tires up? Or 1 on ground the other in the air and turn tire two times and the yoke will turn 3.55 times for a axle ratio of 3.55?

[Long Island RT]

So on a posi rear you would jack both rear tires up? Or 1 on ground the other in the air and turn tire two times and the yoke will turn 3.55 times for a axle ratio of 3.55?

Yep - As John K mentioned above - both wheels off the ground.
Nope - the two times is ONLY for non posi - 1 tire revolution per gear ratio.
That's the whole idea of limited slip (or cheby posi).  Either both wheels better be spinning or none!
If you can spin 1 wheel and not the other - either your limited slip is broken or you don't have one.

[charger2fast4u]

thanks for clearing that up. so both wheels in air when checking a posi/ limited slip diff and only turn the wheel 1 time to get ratio? and a non posi rear you would jack 1 tire up and other stays on the ground and you turn the wheel 2 times for ratio?