I am making one bike out of two. The frame that I want to use had a real seventies-looking Shimano 600 rear derailleur. The components bike has a real nice-looking derailleur marked "ALTUS XT".
The frame I'll use does not have the little hangy-down bracket for the rear derailleur. The components bike's frame does.
Which derailleur do I want to use? The Shimano has the advantage that it's mounted to a little hangy-down bracket thing that bolts onto the frame's axle slot. Thus it is usable; I can just bolt it back on.
If I wanted to use the Altus I'd have to excavate the hangy-down bracket thing from the Shimano -- it's a few parts in -- and I'm still not sure it would fit the Altus.
The answer to your question depends on a lot of things. (The Altus RD, by the way, is Shimano too). Post some pictures of the two installed RDs in the hope that you can entice one of this forum's knowledgeable types to answer (where are you, boudreaux?) How many speeds does each drivetrain offer? My guess would be that you'll need to obtain an RD hanger that can be attached to the rear axle, if such things exist, if you want to use the newer RD with the older frame. How does the older RD attach? To the axle? You will probably need to match the rear shifter to the RD. More information needed.
