i've got a 90 RX7, automatic, converting it to 5spd and i want 4.30 gears and not sure if i have them already. anything i can do to check them?

 

if you have an automatic you have a 3.9 rear end. The only model that came with a 4.3 is a GTUs...

 

dident the vert (of a specific kind, 5 speed, auto, s4 or s5) come with 4.30's?

 

nope. To my knowledge, s5 man. verts came with 4.1, auto of any kind, any series came with 3.9. s4 verts came with a 3.9 nomatter what the transmission was. 4.3 gears only came in a GTUs, I've seen them for sale for $400+ brandnew. I'd always figure If I were to pay $400+ dollars for a new gear set, it'd be a 4.50

 

80 mph = 4000 rpm for the 4.3. Like my GTUs.

and of course auto = no 4.3

 

take apart your rear diff and count the teeth on the gears to see if the ratio is 4.3:1 or not.

 

That would be about the most difficult way to do it.

No auto FC is going to have a 4.3:1 diff unless someone has swapped one in. The easy way to check it to jack up the rear of the car and turn the driveshaft by hand. Count the number of driveshaft revolutions it takes to turn the wheels around once. A 3.9:1 diff won't quite make four turns, a 4.1:1 will make just over four turns and a 4.3:1 diff will make about four and a third turns.