[fredfifty]

what came standard or how can i tell what size rear end i have on my 99 Tacoma ext cab v6? looking into changing the differential

 

[Enola Gaia]

Your 99 V6 5-lug XtraCab has the so-called "8.4" version of the 8" differential.

The final (differential) gear ratio is 3.153.

It's the same for '99 manuals and autos.

This is the same differential and gearing used on 2001 - 2004 S-Runners. If I'm not mistaken it's the same unit / gearing used on 5-lug V6's all the way back to 1995.5.