When you turn one blade do they all move? If not take the top cover off your mowing deck and check the belt inside, Also check the belt idler pulley to make sure spring isn't broken and there is tension, Also when you pull the knob for the PTO have someone look and make sure the clutch is spinning, Hope that helps.

I have a 2166, which is a very similar machine, that had similar symptoms.

For me, it started failing when it was warm (maybe after 30 minutes of mowing). I could let it sit, or spray it with water, and then it worked fine. I ended-up replacing the clutch (about $125 and 30-minutes of time). Before you do that...

First, you mention that you can hear it engage. When these get weak, it will sound like it's engaging, but will continue to slip. Have a helper look to see if the belt moves when the switch is engaged.

If it does, then jimmy56's tips about belt problems is a good place to start.

If the belt doesn't move, troubleshooting becomes more involved, but start first with battery condition - a weak battery might not provide enough current to energize the coil and engage the PTO. Some may suggest otherwise, but attaching jumper cables between the 2155 and a running car, or to a battery charger, are both 'shadetree' tests that I've done. If this works, it could be your battery (how old is it), the battery terminals (they're clean and tight, right), or even some other wire or connector that's not letting enough current get to the PTO clutch. I would make sure you have a good battery, all the wires and connectors are in good shape, clean, and attached firmly. It only takes 1 bad connection or wire to cause problems.

Others may have some suggestions for additional troubleshooting (including jumpering the wires leading to the PTO clutch to a known good power supply), but these clutches do go bad, so it might be time for a replacement.

You might follow the link for clutch testing

Here is a link that might be useful: Link

Thanks for the responses.
I finally got a chance to go out and look at it. I didn't have a helper around, so I used my cell phone to take a video under the deck to see if anything was moving. The belts were turning, but the blades were not. I pulled off the deck, cleaned it up a little bit, and pulled on the belt tensioner a few times, put it back together, and it started working. While driving back to the garage, with the blades engaged, there was a thump, and some metal on metal rubbing/grinding sounds. I shut off the blades, and it continued. I shut off the engine, let it cool down, and didn't see anything obviously loose. I restarted the engine and the grinding noise is still there with the pto not engaged.

I guess my next step is the pull the pto clutch, and inspect it.
Anything I should look for?

Thanks

Just removed the PTO clutch.
Is it supposed to come apart in 2 halves?
I started the engine again, and still have the grinding sound.
So now, I'm not sure where to look next.

Any guesses?

I found the source of the grinding sound. It looks like the drive shaft adapter blew out. Blue plastic looking pieces all around the fan shroud area. Not sure if its part of the driveshaft, or the adapter. Did they really use plastic to secure the shaft to the engine? Or did I find someones bad repair job?

No, your clutch is a piecer. The blue doesn't sound familiar to me.

might try this link to d/l a serv manual for your 2000 series machine..

Here is a link that might be useful: 2000 series serv manual

The PTO clutch is 2 parts - the fixed part that attaches to the engine, and the rotating part that drives the belt.

Sorry, but I don't know of any blue part on my 2000 series.

There's a fan out the back of the motor, on the shaft that goes to the rear end, but don't know of any shrouds.

Take a look at the exploded views on the attached, it should help you track down the problem.

Here is a link that might be useful: Exploded parts diagrams

The blue peices are some sort of rubber or plastic. They fit inside the splines of the driveshaft where it mounts to the engine and to the tranny. 8 at each end. Mine either dry rotted and/or had too much torque and chewed them up.

{{gwi:320132}}

Sorry my post didn't make sense. It is a one piece PTO clutch from what I see. Meaning it should all come off together. less the spacer and hardware. Those must be the roller barrels referenced on page 5 65 of the service manual. Where they are in parts, I dunno.

I don't see the shaft from the engine to the transaxle having anything like that, but the left axle does have:
The larger piece looks like:
Cub Cadet 619-3025 Housing, LH Axle
The blue pieces look like:
Cub Cadet 915-3045 (replaces 715-3045) Bushing, Dowel

Here is a link that might be useful: Parts Tree link to the Hydro Transmission parts for the Cub Cadet 2155

The blue barrels are part:
Cub Cadet 759-3764
Kit, Drive Barrel

Possibly included with the drive shaft assembly:
Cub Cadet 603-0191
Shaft Assembly, Drive

Thanks for the service manual link!

Still not sure about the PTO clutch. Mine came off in 2 parts. Pretty sure its toast.