Rear Derailleur question

My old trusted Univega may be in need of a new RD. I purchased this bike in 1986 and it still has the original drive train on it. I've noticed that anytime I remove the rear wheel shifting problems develop with the RD.

I took it to a local LBS to have it looked at and was told the RD is wearing out and needs to be replaced (has too much play in it). The original components are Shimano 600. Do they still make these (I've not been able to find them online)? If not, can I use another brand of RD? I really don't want to spend hundreds of dollars for a new RD but would like to find a reliable/affordable one to replace the tired one. Any suggestions or ideas?

Thanks!

I have mixed brands on my bikes, and they do fine. (two of my bikes have mixed Shimano and Campy, which is supposed to be a complete no-no!)

For a bike from 1986, you might want to look at what Rivendell has to offer. I've been looking at their "old bike" compatible stuff for my 1987 bike. Their catalog is just full of multi-compatible goodies! Even just the info they have is nice, and makes me feel like I don't need to worry about finding drive train parts that will work. www.rivbike.com

How many cogs in your freewheel/cassette? Are the gears indexed? What kind of shift levers do you have? The indexing is actually in the shift lever, not the RD. You can probably replace a Shimano 600 with an Ultegra or most anything else, as long as you match the cage length to your cog sizes.

DebW, the freewheel has five cogs on it. Shifting is gravity and the shifters are on the downtube.

Pretty much anything will work, as long as it has the right hanger (does your current RD screw into a frame piece or have it's own hanger than mounts on the dropout?). You'll need to know the largest cog size on the freewheel and the tooth difference of your chainrings to get the proper cage length.