I have a Bridgestone Submariner that I bought in 1980 and in great shape. 27 1/4 inch ten speed. Everything original except wheels, tires and rear sprocket. The SunTour rear derailleur has been great, but now the high low set screws are at the limit of travel. I have the H set at less than a 1/2 turn from all the way in and the L set at a point so far out it could fall out. What is happening and can this be repaired?

Check hanger alignment. Having to set it up this way might suggest that the hanger is bent

Worn out rear derailleur? Bent hanger or derailleur?

VGT derailleur - right?

I thought those were built so sturdy that you could use one to pound in tent stakes but I guess that everything has a service life. My bet is that if you grab the arm and try to wiggle it laterally you'll feel a bit of slop. I used to have one in my junk box but I don't know what happened to it.

It is a VX model. I cannot get the high gear to engage (that is the derailleur is on a lower gear, towards the wheel) with the correct cable tension. The only way is to have a loose speed cable. On the forward end of the derailleur when I push on it the play is 1/2 inch and then springs back when I let go.