Yes, I've had weight driven clocks for years.cuckoos wall and grandfather. I think I understand what you are saying. It keeps good time, chimes every fifteen minutes, but the chimes go off five minutes before they're supposed to. Yes?

Are the hands accessible to the touch. IOW does the clock have a glass face or can you adjust the hands yourself?

THe face opens and there is a nut holding on the minute hand. It screws off. But the center of the minute hand has a square hole that fits over a square peg so the minute hand can only be changed in 15 minute intervals. It seems like the whole thing just needs twisted 5 minutes around.

You are right about what needs done. There are two ways to do it and I really, really am apprehensive to give advice on something as expensive as a g'father clock. The new ones have a self-adjusting mechanism the old ones don't and if you try some things with the old ones you can with the new ones, you can do some damage. But essentially to do what you think and I think needs done I found a link explaining it better than I can. So I'll just link you to it. Good luck.

Here is a link that might be useful: clockrepair

Well, I tryed the suggestion on the web site but it didn't work. I think I may need to be clearer. The clock chimes in the correct sequence but it chimes 5 minutes too early. So it chimes at 9:25 instead of 9:30 The hands cannot be only moved 5 minutes.

I understand about the sequencing. And I'm not talking about moving the hands. The hands need to be lifted off and there should be a rod coming up through the dial on which hole through the hand lays and then a nut on which you screw it down to make it fast. It is sometimes square so I also understand why you can only move the hand to four positions by resetting them on that square rod.

But the rod itself rotates steadily, not fifteen minutes at a crack, so there is another tack you can use and here is the exact wording I found on another website:

"If the clock is chiming prematurely only about 5 minutes or so before it is supposed to chime, on most clocks you can just take off the minute hand and turn the bushing that is in the center of the hand one way or another so it is exactly on the hour when it bongs its melodies."

So that means stopping the clock immediately when it bongs the quarter hour chimes. Removing the minute hand and turning the bushing slightly so that when the hands are replaced they would point to the exact quarter hour. That should basically just reorient the hands in relation to the clock dial.

This shouldn't harm your clock whether it is old or has a modern movement, but you should never turn the bushings backward on antique movements. In your case, you would be turning the bushing slightly clockwise, rather than anti-clockwise. That should basically just reorient all the hands in relation to the clock dial.

I was hesitant to suggest this since the only real things I know about old clock movements are what I've observed in my own clocks and watched when we get the clock man in each year to clean and adjust ours. So, do this at your own risk. I don't want to suggest something and you end up harming your clock movement. But, it should work.