low-low is 25.58, 8H is 1.00 and diff ratio 2.25. 4 reverse gears, the 2 lowest are same as LL and LH forward, the high reverse gears are the same as 3L and 3H.

The gears are evenly spaced throughout (and yeah, would be tricky to build a real life one like that).

The idea started out with modelling a 9 speed with 2 axle ratios for heavy haulage but that requires a special shift spec which at the time was a pain to implement, so I made one which uses the Eaton/Fuller 18 speed roadranger shift spec as that's built into the game.

What are the first and last gear ratios (& differential ratio)?

This one is only for stock SCS trucks. It's not hard to incorporate it into any mod which has an open def, and I have no objection if anyone wants it for that

have you added the ironwerx.w900 ?

let me know if it doesn't show up on any particular truck. I think I got 'em all. Feel free to add it to other trucks if you wish