OK ... a couple of days ago I was driving and went to shift from 1st to 2nd and, tada, no 2nd gear. First thought was ..."oh **** a shift cable", as I had to replace one about 6 months ago. But, after checking, it appears both shift cables are unbroken. But, I have no 2nd, 4th, or reverse.I checked the tranny fluid and it is slightly above the add mark, which should be sufficient. Clutch fluid is fine, all others gears shift normally with no grinding. Someone please tell me which direction to go and I promise I'll be your best friend or wash your dog for you or something!

 

sounds like something let go inside the tranny itself.

The Isuzu transmissions are known for being piles of crap. Start hunting through bone yards for a 00-02 cavi/sunfire manual transmission. Its a getrag gearbox, can handle alot more abuse, and has better gear ratios.