the 4th is 29 sleeve gear layshaft is16 .bob upb he supplies lower 2nd gears that used on standard 4th 28th sleeve gear if you look at upb web site I don't know primary size gear somebody else may reply I been looking in mike estall tiger cub bible my front gearbox spocket is 16 I don't know back its bit high gear if go 15 14 it be right not good on road I have no access plate how can cut it out in suite or best strip down done on a mill