Hello all;
If I want to put a 9" front end in a cj, can you use a standard rear 9" differential or does it have to be reverse rotation or something like that?
Reason I ask, I am considering a 9" for the rear and the front, salvage yard has two that are the same ratio. Thanks:)

Standard 9" is all you need

And its called reverse cut gears not reverse rotation

Thanks, good to know.

And its called reverse cut gears not reverse rotation

Depends on who you ask...both names have become en-grained in the industry.

If you want a low-pinion front, you'll want a normal standard rotation diff from a low-pinion 9"...front or rear doesn't matter, the centers are the same.

If you want high pinion, then you'll be jumping into Currie's reverse rotation hi nine (actually 8.8" but in the front, is more than strong enough for most trail applications), like the one shown here: http://www.currieenterprises.com/cestore/curriechpRE.aspx

We run the Currie high nine in the front and a traditional low 9 in the back.

Depends on who you ask...both names have become en-grained in the industry.
Reverse Rotation is slang, and bad at that.
This term only shows the ignorance of the person or company using it.

What part of the axle travels in a "Reverse Rotation" as compared to a normal axle?

Just because some people use it, doesn't make it correct.
Heck, I've been told the pumpkin on my front Dana 44 is a "Rear end"
"Reverse Spiral what? No, that is high pinion."