Bought used. Tested it and it worked perfectly with no water, no load.
Very quiet and agitation, spin "seemed" perfect.
With a load, agitates, spins dry. But on agitation it makes a loud "knocking" noise with each cycle. Louder on heavy agitation. Annoying.
I have a hard time accepting this as an acceptable noise level but maybe it is?.
Spins quietly at high speed, dries with no issues fully loaded.
I've replaced the dogs [even though they were OK].
The agitator looks fine, the block bearing [under the agitator] is tight and looks new.
I don't mind replacing the transmission if that's the issue but would hate to just start throwing in parts.
How can I further test the transmission?
Or can anyone provide a better clue on what is "knocking" under load?
Thank you.

I experience the exact same symptoms with my Whirlpool washer. (actual brand name is Kenmore, model =110.82870120) Works and sounds just fine in all cycles with no load but add a load of clothes and the loud knock appears during agitation only. Interestingly enough there is no knocking with load under the "Delicate" setting. (just normal and Permanent settings) I too tried replacing the dogs and the brake cam to no avail. Not sure what to try next. Tough to keep throwing money at it when you are not really sure. Maybe the transmission, motor drive coupling, clutch, drive block, something clogged somewhere??? Anyone?

I am helping a friend who has a stacked Kenmore washer dryer. The model number is 417.9782700. The washer is making a loud click clack when the agitator is moving back and forth. Everything else works fine and there are no other problems. I took the agitator off and could find nothing worn or damaged. Is there a coupling inside under the tub or is the problem likely in the transmission ? I am hesitant to tear it apart as the local dealer says the model number is incorrect but I double checked it. I cannot find a manual for it online and parts info for this 5 year old machine is not available either. Need help before this click clack becomes a clunk clunk. Also can the washer be worked on w/o removing the guts of the dryer ?

Someone at the mfg must have been playing a trick on us as I checked the model number twice and my friend checked it also. I will go back tomorrow and recheck it again. Any ideas as to the cause of the click clack noise ?

I have to apologize but I missed one digit in the model number.
The complete model number is as follows:
417.97812700
The question still remains the same. What might be going on to make the click clack when the agitator is working ? Also where can I find an illustration showing the parts layout ? Also can this machine be worked on in place or does it have to be moved out of the house and dismantled ?