My Howard Miller floor clock strikes each hour correctly until 11 or 12. Then it strikes 1 hour behind. What could cause this?

OK, google is your friend, but before I go there, recognize that pendulum clocks are generally regulated by the speed/period of the pendulum. A shorter pendulum has a shorter period/faster time and vice versa. So in general, look for the length adjustment of the pendulum weight.
Specifically, here is a link to a google-d search:
http://www.howardmillerusa.com/customer-support/how-to-setup-howard-miller-grandfather-floor-clock.html

Hello Shirley Haas,

Leave the weight fully extended (stop the clock)
and start checking your local area for clock-smith
that make house calls (run on hour strikes are much more common... but whatever you say... "CHIMES" the cause
is likely the same: Little or no maintenance).

http://www.ebay.com/itm/Howard-Miller-Grandfather-Clock-Movement-with-Dial-Model-610-309-serviced-/282379781809?hash=item41bf2586b1:g:UO4AAOSwMmBVjdo-

These clocks need to be lubed and serviced and it is work
best left to the serious professionals.

You can probably get away with another 35 years...

Remember we have time on our side...

As for me...
I bought a junk clock to EXAMINE & fix (did)
I purchased synthetic clock oil (LIBERTY noted below)
and lubed ALL the obvious spots...
wiping excess away with Q-Tips.

Then I assaulted my own RIDGEWAY...
Got it running & regulated (was NOT my problem)...
My pendulum only needed to be centered correctly
(oh well).

I could NOT pull up YOUR 610-808 movement... but on the movements I have done you can see the hour strikes & the lever that triggers that motion (HOURS are each a spike on
the gear wheel... from one (^), 2 (^^) to 12 (^^^^^^^^^^^^)
progressively (pretty obvious if you are looking).

Go there... look... lube..!! Be gentle... VERY GENTLE...
or better ... call in a QUALIFIED SERVICE PERSON.

Carnac the Magnificent

It sounds like it may have a tooth that is damaged on the counting gear in the strike train. You should take it to a clock repair shop.
UsedClockParts.com

Gently move the hour hand to the 2 O'clock position, then using the minute hand cycle the time forward until it is at the correct time.

Tim
Main Page

Move the hour hand counterclockwise two hours back and then just move the minute hand clockwise until the correct time is set.

UsedClockParts.com

The next time it gongs multiple times turn the hour hand clockwise until it is pointing at the number of times it gonged. Next take off the dial nut off (make sure to put it in a plastic bag because they can be hard to replace) and turn the minute hand until it strikes once. Now put the minute hand back on pointing to 6 o'clock and replace your dial nut and you are all set.
Fix Clock That Gongs Wrong

You'd have to take the dial off so you can see what's going on in there. Your movement, (probably a Kieninger) has what's called a rack and snail that determines how many times the clock strikes.
It sounds like either the racks being prevented from falling further than the five position. It may just need to be cleaned, and oiled (with clock oil), or something may be damaged.
It would probably be less hassle if you called a clock shop to service it for you. If It were in front of me I could tell you more.
Good Luck

Try pulling the batteries out, set the clock to 5:45 then put the batteries back in. Set the time to 6:00 and count how many times it strikes. If it strikes 6 then your good. If it strikes a different number say 5, take the batteries back out, and set the clock to 4:45 then put the batteries back it, set clock to 5 and count the strike. Most quartz clocks reset their chimes to 5:00 when new batteries are installed regardless of the time shown on the face. I hope this helps. Good Luck.

The next time it gongs multiple times turn the hour hand clockwise until it is pointing at the number of times it gonged. Next take off the dial nut off (make sure to put it in a plastic bag because they can be hard to replace) and turn the minute hand until it strikes signaling 15 minutes after. Now put the minute hand back on pointing to 3 o'clock and replace your dial nut and you are all set.

Fix Clock That Gongs Wrong

We understand your question:

The hand has a center bushing with the square hole in it.Remove the hand and use a pair of pliers on the bushing in the minute hand then re-clock or rotate the bushing back on the quarter hour then replaced it back on the clock.

Hope this tip provides some workable ideas for this repair.

R/
David

Orlando