how do I tell what I have

[Scamper]

I just bought a used roadrunner 8 3/4 rearend all I want is the gears.
I see 742 casing and I am told it is a 4:10 posi.
The old way was to turn the tire and count the revolutions of the drive shaft.
There are no tires and the brake drums feel like the brakes are up tight. any ideas would be appreciated since I just bought on good ol faith.

Donrayer:

 

[pettybludart]

Your gonna have to pull the axels,unbolt the pumpking(center section)once out the gears should have 4.10 stamped on them.Good luck

 

[Scamper]

how do I do this please?

 

[Rocky_JS]

count the teeth on the ring gear should be 41 and the pinion gear 10. 41/10 = 4.10

 

[swinger340]

count the teeth on the ring gear should be 41 and the pinion gear 10. 41/10 = 4.10

X2, will sometimes be stamped on the ring gear as well.

 

[Bulldozer]

if you can pound the drums off, or you can clip the brake shoe retainers on the backing plate, you can still count the revolutions of the yoke as you are spinning the axle

 

[Scamper]

Thank You for the advice. I will now have the fun of unloading the rear by myself from the Durango, then to figure out what I bought. It was a fun day yesterday, gears-new be cool rad-flowtech ceramic headers-camshaft,lifters-wiper seal kit ordered from shumachers and a complete gasket kit for entire car including front and rear windshields-flowmaster mufflers