How to Troubleshoot & Replace Whirlpool AP6008904 / WP3951632 Washer Lower Agitator

The diagnosis was the longest part of the repair, but I found out that the splines on the inside of the agitator had stripped out, so the matching splines on the drive shaft of the washer were not spinning the agitator as they should. I bought just the bottom part of the agitator from this site, and it matched perfectly with the old top part and the drive shaft of the washer. The actual repair just took 5 minutes. 

Needed new lower agitator because spline stripped out after 3.5 years of in home use. 

I ordered a new bottom agitator 

I ordered the bottom agitator. I am a woman and fixed this on my own. Finding the part on the site was easy. 

Replaced the lower agitator 

I removed and inspected it. The plastic teeth on the lower agitator were worn out. I replaced the lower agitator and it fixed the problem, Yippeee! 

Was not familiar with proper operation or design of machine, so got on Youtube to see several troubleshooting & repair videos. Started troubleshooting my machine and eventually removed agitator from the shaft. Found the splines on the agitator to be stripped. Order a new agitator to by ground in 4-5 days, and it arrived the next day instead! Very pleased with that. Put the new agitator on within an hour of receipt and my wife feels like she has a new washer (no telling how long it had been degrading in performance). I did clean up the shaft area while agitator was removed. I also cleaned the bolt and drove the bolt in and out of the shaft (with a little WD40 to help) to make the mating of the two smoother. The bolt was fairly hard to remove originally (gummy). Once the bold freely entered/exited the shaft, I reassembled the new agitator. I also checked the washer on the bolt and though it had the impression of its mating part on the agitator, I did not replace it (it was not torn or frayed). 

Replaced with new lower agitator. VERY fast delivery and easy fix! 

Removed all upper parts and inspected upper agitator pawls , pulled lower agitator straight up & out , it was obvious what the problem was . before installing new agitator i cleaned steel shaft splines with a pick and wire brush to ease installation of new part . part arrived super fast and was back together in 10 minutes . thank you for taking my order , a very kind and knowledgeable staff , videos were very helpful 

Three of the 4 tabs on the top of the agitator were snapped off. The cam assembly was also missing. I purchased all of those parts and replaced them easily.