i have a '94 tracker that i want to take the whole 3rd members out of and put in my sammi.  i'm going to run 31's or 33's on it.
do the tracker gears just drop right in or do i have to do any modification?  also if i use the 4.62's what difference does it make on the highway as far as engine rpm compared to using stock gears w/ the 31's or 33's?

The chunks from the Tracker won't just bolt in...the front will, but it's an aluminum case, ans without the brace they have in the Tracker, they break pretty easy.
The rear gears won't fit at all without the hybrid axle housing(uses Samurai axles offset, with the larger Tracker center section). The front ring and pinion gears with fit in the Samurai housings(there is a shim, and sleeve kit  that some of the vendors carry that make it work better).
For 31s, the 4.62s should be almost perfect. I have the 5.12 Tracker fronts in mine with 31s, and the low 5th gear trans, and I am wound up tight on the highway...so the 5.12s are too low for 31s.

try this link:
http://bbs.zuwharrie.com/content/topic,3975.0.html