rear-end problem

(the car's, not mine)

The right rear spring (I thought) on my '71 Mach decided to crap out last week - luckily, just after I got off the interstate. I was getting a "rub rub rub" sound from the RR. The car was sitting visibly lower on the right than the left. What the heck, I was planning on changing the springs anyway this winter, but I hadn't planned on getting the car towed home to do it (thanks, Hagerty!).

I changed the springs out (after an epic fight with a rusted front bolt), and the ride and height are exactly was I wanted. Unfortunately, as I was test-driving the car, the "rub rub rub" sound came back after a couple miles of no sounds. This time I drove slowly back home, and noticed a pattern where the noise was "rub rub rub" for a few seconds, then a sound as if a spring is tightening, then a POP, and the sounds all went away. After 10-15 seconds, they would start again. No change in handling or driveability.

This could be the brakes, but there's no indication of dragging or problems stopping. I'm thinking it may be the axle shaft bearing causing a problem (it was screwed up when I bought the car; I had to replace the axle shaft it was so badly worn by a spinning bearing on it).

Obviously I'm going to take the the axle apart. But I'm throwing this out there so maybe somebody has an idea or two what else might be the problem.

Jeez! Don't see you for a couple months and the car goes to hell?!

Hey, we still need to get lunch. Gonna be around next week?

Later next week, yeah. Monday night I have to go in at 0130 for some software updates, so I'm gonna be wiped out until Wed or Thu or so.

but the rear on jacks/axle stands, put the car in drive and listen underneath if you can here something, just remember the turning wheels!!!

I wouldn't be able to hear my rear end with the motor running!

I did talk today to a very knowledgeable guy who's very familiar with the Ford 9". He told me it sounded very much like a spider gear in the pumpkin. I'm inclined to agree. It's the original rear end and the only thing I ever did to it was new axle bearings and seals. I'm going to pull the pumpkin and either rebuild it or buy an already-rebuilt one.

Jack it up (with the car off) put it in neutral and manually rotate the wheels. Should feel/hear something

I did try that. Sometimes I would feel a slight "rumble", for lack of a better word. However, I never did hear the grinding noise. I don't think that's very conclusive, though, as sometimes I can drive the car a few miles, and the sound happens once or twice then quits for a while. Unfortunately, it's not something I can duplicate.

When I pull the pumpkin, I'm also going to thoroughly check the u-joints, even though they're only 3 or 4 years old, while the pumpkin is 42.

I wouldn't be able to hear my rear end with the motor running!

I did talk today to a very knowledgeable guy who's very familiar with the Ford 9". He told me it sounded very much like a spider gear in the pumpkin. I'm inclined to agree. It's the original rear end and the only thing I ever did to it was new axle bearings and seals. I'm going to pull the pumpkin and either rebuild it or buy an already-rebuilt one.

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try using a stethoscope, they are pretty cheap and can be very useful in these types of problems..