Handle too loose after replacing Symmons temptrol shower cartridge

[neoteric5]

I just installed a new cartridge spindle assembly (TA-10) in my Symmons pressure balanced shower valve. After replacement, the spindle is now too loose, so that the weight of the lever handle causes it to droop to the bottom position, making it hard to set the temperature mix. The old spindle was not too loose. I didn't add any lube to the spindle threads and didn't touch the anti-scald screw on the cap. What could be causing this problem?

I hope I don't need to replace the valve seats, because it looks like I would need to buy the seat removal tool, too!

 

[journeyman]

You should always replace the seats

 

[neoteric5]

Thanks for the recommendation. I called the vendor of the valve trim, Waterworks, and they said that there is a packing nut that is supposed to provide additional resistance to the valve spindle when the whole thing is assembled. I hadn't put the whole thing back together yet; when I did, the looseness went away.