Quote
the truck came with 235's, and it has 4.10 gears. the problem that i have is that before i got the truck, someone else put in a speedo cable for a truck with 31s. i want to upgrade to 31s, but dont have the money.

This shoudn't effect your speedo at all, unless the PO actually changed the gear at the back of the speedometer, which I am not sure it can be done that way with the Yota's. Changing teh cable alone wouldn't/shouldn't have had any effect on the speedo reading. Now if the PO changed the diffs, than it would through the speedo off by as much as it is.

To determine what gears you have, you can lift a rear tire, mark a spot on the driveline, and see how many revolutions of the d-line it takes to turn the tire one full turn. If you have 4.10's it will take 4 full turns and about a 1/10, if you have 4.56's it should be about 4-1/2 turns.

More than tread lightly. Leave it like you were never there, nor anyone else.
'90 X-cab 4.88's 33 BFG AT's, rr ARB, Headers, Ignition upgrade, cold air induction.
'91 X-cab 5.29's 315's BFG MT's, rr ARB, custom bumper and flatbed