Why won't my tranny engage on my jeep?

So I was driving behind a bus and as it hit the brakes, I put my 85 jeep cj7 renegade 4 speed into neutral, and as it sped back up I put it in 3rd and hut the gas while dropping the clutch. The engine revd but my jeep didn't go any faster than rolling down the hill in neutral. I thought my clutch plate had busted so I opened it up, the plate and cable and everything else was fine. Next I checked the rear differentials, they were good to go as well. I am assuming at this point that my axle splines are stripped, but don't have the equipment to check. None of the gears engage at all, but he rest seems to work fine. What could be wrong?