Can't figure out - 1996 K1500

Can't figure out what the problem is with my 1996 K1500.
Whenever I accelerate it makes a sound that I've always heard described as "lugging" the transmission. It also does this when I come to a stop. Also. when I hit a high speed (55+) it makes a high pitched whine. Occasionally I'll hear what sounds like the grinding noise associated with manual transmissions (when the driver shifts without pushing in the clutch) - only mine is an automatic. I can't duplicate the sound when I step on the accelerator if the truck is in park on neutral.

I checked the tranny fluid twice - hot and cold - and it seems fine. The only thing I've noticed was a very small puddle of fluid dripping from the front and rear axles - but only about 2" wide. Just had the rear axle seal replaced about 6 months ago.

Any suggestions on where to start? I know this is a vague description, but it's all I've come up with so far - any advice would be greatly appreciated.

small puddle of fluid dripping from the front and rear axles, that is a good starting point. i would check the fluid and change. if you have shavings in eather axle you mite be looking at rebuilding them. i would also check the u joints.

Sounds like you could have a problem with-in the transfer case, Make sure the shifter didn't get bumped and not fully in gear.

Needed to get my truck back on the road so I took it to a local mechanic. Said that the differential cover was badly rusted and causing the leak. He changed the rear cover and replaced both axles' fluid. The noise got much better - almost gone. He also said that I should start looking for a new rear end. Just wanted to post the "fix."

the whine is the gears and bearings and usually when it whines its time to either rebuild it or get another if it is 4x4 get the same gear ratio as the old one or you will tear the front end out as the rear will not be matched to the front should be a tag on your rearend telling the gear ratio.the other rear end needs to be same tag on it

Thanks for the info!