I took the cover off my 7 1/4 rear end, expecting it to be full of metal shavings (because of the noise).
I drained it into a plastic paint roller pan and ran a magnet through it and the bottom of the aluminum housing.

No chunks, no ferrous filings or dust.

Does that mean it's not the pinion that's making the noise?

I cleaned the nose and bottom of the housing a couple days ago and there's no leakage from the front either.

This is the first time I've taken the cover off one of these things, so sorry about dumb questions...

The lack of metal just means the gears and bearings haven't eaten themselves yet. Unless you disassemble the rear axle and pull the pinion and it's bearing you won't see what you need to see.

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Joshua

Just taking the cover off taxed my disassembly skills. I think I'll pass on taking apart the whole thing.

You know, it's been noisy for a few months now. A couple thousand miles. Shouldn't they be chewing themselves up by now?

A low rumble, sort of like the sound of a long heavy train, is a bearing somewhere in the rear. When you grab the driveshaft at the pinion, is there any play? (up and down, or side to side) The play rotationaly is the backlash between the ring and pinion. Backlash will make a diffrent noise, but once backlash is set when the gears are installed, it is set for the life of the gears. Take some spray can cleaner and a strong flashlight and lok at the brgs on the sides where you can see without taking it apart, if they are dark or blue, they have been hot. Was it run low on fluid? ? Consider popping the axles out too as those brgs are usually the first to starve for oil.

WARNING DONT TRY THIS AT HOME !!!
At the shop I work at we put someone in the car on the lift up in the air and use a stethoscope to find the source of the noise. The stethoscope is only about $5-10 at a parts house. Trying to run a car on jackstands isDANGEROUS AT BEST You would ofcourse need to put the cover back on and refill with fluid first.


hope this helps you some
good luck tophat

Don't worry about me.

I've been afraid of large, heavy machines or anvils falling on me since I was traumatized by a cartoon.

I'd be too afraid to be the stethoscope guy in your shop.

Make sure to check your rear wheel (axle) bearings, too. The 7.25" rear has only caged ball bearings for the axle bearings, and you may find that these have disintegrated sometime in the last 30 years. Bad axle bearings can sound like a problem in the differential while driving.

Also, driving around with bad axle bearings can be dangerous. On the non c-clip 7.25" rears, the bearings are basically all that is holding the axles in.

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'68 Dodge Dart 4dr Sedan

I wrote this having ridden in the car in question and knowing what a bad pinion bearing sounds like. sixsignet needs a pinion bearing or a new rear axle assembly.

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Joshua

I'm just dense.
I don't get how all that noise over time didn't translate into metal filings.
I expected to see evidence.
Hey, but I don't really understand how they work anyway.

I have a bad noise from the rear axle area.
It's been diagnosed as a bad pinion.

Is there anything that I can learn from it so that I can identify the same problem when I'm shopping for a new one?

Something that I can measure or feel or see.

Oil condition has been ruled out.

About all the inspection you can do is pull the inspection cover, look for damage and check the pinion and axles for excessive play. Chances are you won't find a noisy pinion bering if you can't drive the car.

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Joshua

What happens if I just let it go until next year?
Do these pinions deteriorate suddenly from being noisy to breaking?

If you are going to repair the axle you have I'd have it fixed soon. If not feel free to drive it until the car won't move any more. The gears sound fine now, but if the pinion bearing goes completely you'll ruin the ring and pinion. Talk to Buff at Paden Drivetrain and ask what repairs would cost.

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Joshua

I plan to swap if I can find a suitable replacement.