Have an old, in good condition 5 string banjo without a 5th string tuners and the 3rd tuner, Thinking about replacing all tuners with good geared tuners, but I am a bit hesitant as this is an old (100 years old) banjo and although is a player, not for collecting dust just wanted to get some opinions.
With a little skill and patience that old tuners can be made to work just fine, especially if you are using nylgut strings. What kind of tuners are on it? Do you plan to use steel or gut strings? The banjo was probably made for gut. Do you have photos you could post?
Well, any changes in the structure of the banjo will lower the value of the instrument, at least as an antique/original item. Thus, reaming the peg holes and installing new geared tuners will have that effect.
I've heard that "Pegheds" are a good choice. They're violin tuners with an internal gearing mechanism. There's also a fifth string Peghed. They may require some reaming, though. Friction replacements may be available, too.
My old banjo has its original tuners. They can be a pain, but I live with it to keep it in as original condition as possible. For fine tuning I use Suzuki tuners slipped over the strings behind the bridge.
Nylguts are a poor choice as they stretch and break too much - they would be a particularly bad mix with ancient friction pegs. "Chris Sands Classical Banjo Strings" hold tuning better and don't break as often.
Many old 5 strings can be played with light steel strings (9,11, 13, 22,9) would be a logical starting point. Still, if the neck is at all dodgy nylon would be the best route.
Pegheds would also be the best route for geared tuners. They would have to be installed by someone who KNOWS WHAT HE IS DOING. Which usually means a violin repair person - look for the guy the local "fiddlers" go to instead of the guy who does the local classical players - he will probably be much more willing to do the work. Besides not needing severe reaming to fit them Pedheds are as light as wooden friction pegs - so your banjo will not become "neck heavy".
There are 2 models of Peghed 5th string pegs and they are better than any of the big mechanical looking banjo pegs I've ever owned. I have the "long model" which sticks out pretty far - but I like the look, and especially the feel. The banjo in my avatar "Jackie-O" is going to get a set of Pegheds soon - I put the current ugly bluegrasy looking tuners on her 30 years ago, when they were the only geared tuners you could get that would fit into friction peg holes. Pegheds come in 3 diameters so there will be one to fit your banjo.
BTW I am not involved in the company in any way. Between my wife and I we have about 6 sets of their tuners though.