I'm looking at buying a local yota pickup.
Specs: 91 SR5 5-spd 4x4

What trans & t-case does it have? What's 1st gear, 4x low, and what are the diff gears?

Thans a bunch.

 

Nothing. I like it. I don't know much about the truck but I'm sure there are a bunch of others that can help you.

 

gears are either 4:10s or 4:56s. most of the models that came with stock 31'' tires were loaded with the 4:56s

 

What engine? 4 cylinder or 6?

 

SR5 package came with the 3.0

 

Should be an r150 hooked to a chain drive case.
The transfercase is actually slightly lower geared than a gear drive, but I don't remember the number; 2.93 vs. 2.8 or something like that. First gear in the tranny is 3.83.
Check here to get info so you find out the differential gears it came with:

http://www.brian894x4.com/Gearratiosanddiffs.html

 

sr5s didn't come with 3.0s. it's just a trim package after '83 on 4x4 trucks.

it can be a 2.4(which would have a W56 and a gear driven case, or a G58 with a chain driven case if it has ADD) or a 3.0(which would have the R150F/chain case)