I have a 9 year old 9spd Ultegra Triple and the front der is getting cranky. It shifts fine from the little ring to a bigger ring, but won't downshift well. I can push it down by hand, (or push it with my foot if I unclip but it doesn't shift well.

I think that this is from getting gunked up. In the past when this happened I cleaned it well, or even took it off and soaked it in some carb cleaner and it would be better for a while. I wonder if it's just old and the spring is weak.

Am I better off just replacing it? Will a 10spd front der work fine with my 9 speed setup? (In case I want to upgrade to 10spd someday)

Thanks