Whirlpool and contract buyer-resellers like Sears Kenmore know the seal they've been using between the circulation pump and its driving electric motor have been failing at a VERY high rate for years, yet they have not replaced that seal with a better design nor adopted a 2-stage seal. Worse, they know that when (not if) these seals fail, the motor shaft they have been using is rust prone and the roller bearing they have been selling is also rust prone. Given that these machines sell for hundreds of dollars, for very little more production cost, they could have used a stainless steel, motor shaft and a stainless pump-side bearing. That would have GREATLY improved these machines. If you are replacing the pump-side motor bearing, so spend a little more to get a stainless steel bearing. Bearing numbers start with 608 and have 22mm overall diameter, 8mm inner diameter, and 7mm wide.
John

I received an automatically-generated email alerting me to the new comment in this discussion thread. Congratulations to the site creators. That feature is working well.

As it see it, dishwasher buyers are justified in expecting that these bottom-mounted washing solution pumps should be capable of pumping quietly but powerfully for thousands of generally trouble-free hours, and not leak washing solution on their floor nor into washer parts which will certainly rust and degrade if they become wet. That buyer expectation set presents one very tough design task.

The first part that generally fails is the seal surrounding the pump-driving shaft. The pump side MUST be wet to function. It's a simple centrifugal impeller. Yet the other side of that seal MUST be kept dry if the manufacturer selected parts which are 100% certain to rust and degrade when repeatedly wetted and heated. One rational solution would be to overtly recognize that those seals will eventually begin seeping, allowing a slight amount of leakage. Then attach a moisture-slinger to the dry side of the spinning shaft, surrounded by a moisture catcher that drains into a bottom evaporator try, similar to evaporator trays commonly found under refrigerators. That could prevent slowly degrading pump seals from slowly destroying a rust-prone shaft-support bearing.

Another strategy is to use a stainless steel shaft-support bearing on the motor's pump side. The motor's shaft-support bearing on the other end is not subject to becoming wet, so that bearing doesn't need to be immune from rusting. For a genuinely "premium" model, I'd suggest that the motor shaft should also be stainless steel rather than rustable steel.

Now, as an end user, you can simply replace that whole poorly-specified collection of parts commonly described as the pump for a reported $148. That will only restart the same inevitable self-destruct process. Or, you can buy a stainless steel bearing and find suitable replacement seal to create your own much more durable rebuilt pump. Cost for a stainless steel bearing is more likely to be at least $6 rather than $2 for a common steel bearing. I gave dimensions above.

If that bearing can "wiggle" on the shaft, it is probably so loose that it allows the motor shaft/armature assembly to go into a very noisy resonance. As to how these should be replaced, that depends on how mechanically bonded the inner race has joined to the motor shaft. Don't be surprised if you have to cut that old rusty bearing from the motor shaft. Then use a file or abrasive paper to clean the shaft enough to accept the new bearing.
Good luck.
John

The instructions are attached to the reply.

- The whole pump & motor assembly Part number: AP4434612

Just wanted to say thank you for sharing your diagnosis and repair with us. It's not often we see a bad noise created by a vibrating rigid pipe, so your post was very illuminating and instructive.

Thanks again and good luck with your dishwasher.

Gene.