Toilets, Sinks, Showers, Tubs and Disposals - assistance in replacing an AS actuator assembly

I've got a 30-35 year old American Standard toilet that needs to have the actuator assembly replaced. Symptom is that when I flush, the actuator tips back beyond the point where the actuator can fall back and enable the toilet to refill. As such, I have to jiggle the handle a little to get that to happen. I've looked at the plumbing supply websites and I'm "assuming" that the part I need is the "Actuator for Old American Standard Toilets". I looked at the #4 and #5 AS actuators and I'm guessing they are for more modern AS toilets than mine. So I'm basing it on the age of the toilet. So before I do this, I have a couple questions that hopefully someone could answer as this will be the first time I've replaced an actuator:

1) How do these actuators fail...in other words, what on the actuator causes the assembly to tip back beyond the point of resealing the toilet?

2) How easy (or hard) is it to replace the assembly? I've been on a couple other sites and some posters reference leaking problems at the base after replacing one of these.

3)Does the whole assembly have to be replaced or can the base of the actuator be left on and the rest of the new actuator be fitted onto the base of the old actuator?

As always, thanks for any help with this!

Actuator? Sounds like a fancy word for a flapper. Can you describe what it looks like, and how it connects to the handle? There are different types.

You may be able to cure your problem simply by letting out some chain (or plastic strap...whatever it is you have that connects actuator to toilet handle) to create more slack so that when you push the handle down all the way, the tipping of the balance of the "actuator" doesn't make it rock back as far.

On second thought...this may not help. You might check to see if yours has some kind of adjustment to it. Some more expensive flappers do. Describe your device. You may be able to swap yours out even for some other brand that won't cause this. Does your actuator hook onto the overflow tube by ears on each side?

Thanks for replying. Older American standard toilets have an actuator in place of a flapper. it looks like a big black thing with a round tube on top that the chain attaches to, when you flush this toilet the actuator seams to lay on it's back for a few seconds and then drops back down, and the tank refills. On the bottom of this actuator is a rubber disk, this disk is like the regular flapper in other toilets, minus the "ears" that attach to the fill tube.
I have tried giving the chain some more slack with no success, and as far as I can see, there is no adjustment on it. I'm guessing that the way these things should work is that when you flush the toilet,when the water empties out of the tank, the round tube (which has an opening on, I believe both sides) slowly also empties the water that inside of it out the bottom giving the actuator more weight at the seat disk, thereby forcing it down to seal the tank and let water in-like a regular flapper, but I have no idea why AS ever devised something like this unless the extra weight insures a better seal. My problem is that the actuator, when flushed tips too far back, so even when the water empties out, it can't close....normally, I'd say the actuator tips back about 70 degrees. It now tips back about 100 degrees.
There's a picture of one of these units at the following link...

http://masterplumber.net/how_to.htm

Thanks again!

I've worked on toilets with these. But off hand can't remember what the cure is for the problem without taking a refresher look at one in person. I even remember the very problem you are talking about, happening. I can't remember if water sits in this tube for a while and drains out or what. But go here to the site:
http://masterplumber.net/how_to.htm