I can manually turn the blades inside the glass pitcher and I can turn the piece on the top of the motor base into which the pitcher blade attachment fits.

If the same problem exists when the pitcher is not on the base, the base needs to be replaced. It could be that the blade bearing is dry/rusty. In that case replace the blades. Either way, continuing to run the unit in this condition will fry the motor.

Sounds like the gear is stripped inside

Make sure the blade assembly is put together in the correct order. The blade needs to go through the gasket so that the order is pitcher glass, gasket, and metal blade base. Then the final plastic cap threaded onto the pitcher. If the gasket is not between the pitcher and the metal blade assembly, you will have leaks.
Also, check the gasket to be sure it's not cracked and that it doesn't have residue on it.
I hope this helps. If it does, please come back and rate my suggestion!

the older glass jar blenders were sold as a complete ***'y too.
no separate parts were available. i'm sure the stainless jars are sold in the same way...complete.

Does the motor still work if you take the pitcher off of the base? If so, the rod that's in the blade assembly is probably corroded. The blades are connected to a metal rod that passes through a brass tube through to the piece that makes contact with the motor when you put the pitcher on the base. The grease wears down eventually and if you don't pulse and run the motor for a long time at once, the heat can corrode the bar and cause the blade to stop spinning. You can either disassemble the blade unit, or buy a new blade unit online. google blender parts and you can get one for $10

Depending on the age of your blender, a new blade assembly may be available. I would recommend calling Kitchenaid Customer Service for pricing. Their toll-free telephone number is:

1.800.541.6390

Check and make sure that the shaft in the base housing spins. If it does, the blade assembly has become disconnected from it's shaft probably due to an improper spot weld or peening of the blades to the shaft, or has torn loose or ripped the splines out due to an immovable object trying to be spun. A jammed ice cube can do this. Blade assemblies can be had usually directly through the manufacturer and usually on line. If this has helped, please rate it accordingly.

I was just able to fix mine. You'll need the following: two wrenches (almost any type), steel wool, and vegetable oil.

1. Clamp the hexagonal nut inside the bottom of the pitcher with one wrench and place the jaws of the other wrench between the "spokes" of the wheel at the outside bottom of the pitcher.
2. Turn either counter-clockwise until the hex nut comes off. At this point, you should be able to pull the bottom piece out from the bottom. Pay attention to the order and orientation of the parts inside the pitcher as they may fall out now.
3. Dry off the shaft and rub it with some ordinary steel wool (think SOS pads).
4. Twist a small amount of the steel wool and run it back and forth through the hole the shaft goes through.
5. Wipe both clean with a clean cloth or napkin.
6. Rub a little vegetable oil on the shaft.
7. Place the shaft back in the hole and test the movement. It should be like new again.
8. Reassemble the blender.

Hope this helps,

John

the top rubber piece could be worn enough that it is not engaging the pitcher. look at it carefully and see if the "teeth" of the rubber disc on top of the base has not cracked and worn away. a picture of the new one can be seen on the parts websites to compare I spent $10.00 for my replacement but i found them at other sites for $6.00. you will need a very skinny 7mm open ended wrench to get the old one off and it is left handed threads that means clockwise will loosen not tighten the part.i ground down my wrench but an ignition wrench from an auto store will usually be thin enough to reach the flats on the shaft under the rubber disc

you may have stripped the motor gear sek out a new unit