How can I tell what gears I have?

[teamsmith]

I found a local guy with an 8.25 running 3.55 gears for cheap. How can I tell what gears are in my truck?

 

Also, aside from rewelding spring perches, is there anything else I need? Can I reuse my driveshaft?

 

Thanks

[Minuit]

Since your sig says your truck is a 4.0, 5 speed, you can bet on it having 3.07 gears. There may still be a tag on the diff that confirms this.

[teamsmith]

ok thanks, I'll look for the tag. I figured I could lift the rear end and count the rotations but the difference between 3.07 and 3.55 might be within the margin of error on my slide rule.

[onlyinajeep726]

Get the axle anyway and find a matching geared D30 for the front.  If you decide to run bigger tires, the taller gears will help.

[Pete M]

 jack up one rear tire, put the trans/tcase in neutral, rotate the raised tire around twice while counting the times the driveshaft rotates.  about 3 times is 3.07, 3 and a half times is 3.55, etc.  make a mark on the driveshaft to make it easier.  if the rear axle is a posi, then you'll need to jack up both rear tires and rotate the tires around once.

[teamsmith]

Thanks. I may go ahead and pick it up. At only $100 for a drum-to-drum 8.25, it seems too cheap to pass up. It looks like I will one day be replacing the whole drive train since an AX-15 swap will require a TC and bell housing.

 

Can I reuse my existing driveshaft? I currently have no lift (probably negative lift with my tired springs and blown shocks) but one day I will probably do a 3" lift.

[Timeless]

The input on the 8.25 is longer than the dana 35, so you most likely cannot reuse your drive shaft without lifting your rig first.