I poured in some Prolong before going on a long 400 mile trip and coming back. Well on the way there we noticed some weird clanking and sometimes grinding sounds that seemed to come from the rear driver side tire when driving. A few days later I took it to my local mechanic and he put it up and put it in drive. I noticed that the rear driver side tire, where I heard the noise, wasn't always spinning as fast as the other tire. Sometimes it would come to a near stop and then go again. The other tire would keep spinning at the same speed. Then he pulled on some wires near the tire and when he did that it would speed up and it would go at the same speed as the other tire. This seemed to fix it. Then he would pull on another wire and it would make the other tire stop.

He talked to another mechanic and he says that I need a whole new rear end. Do I really? It seems to me that he was able to temporarily fix it by pulling on a wire. Why was that? Also he checked for gear oil and that reminded me of the prolong that I put in. Could the prolong stuff could have caused it, or the fact that we were sometimes driving as fast as we could on our long trip? I was thinking if there's something wrong with the bearings then I just need to replace those, right? Do I really have to get a whole new rear end? If I drain out all the tranny fluid and replace it, might that fix it? How much is a rear end going to cost?

The standard rear end only has one drive wheel, so as far as I know it is normal for only one wheel to spin unless you stop the other wheel. The cable he was pulling on was the parking brake.

I use Prolong in my Chrysler but I use the engine product and don't know if there is a product for rear ends. If memory serves well, there are hypoid gears in them that need proper lubrication. It sounds like a spider gear problem to me, but I am not an expert. One of our other "sages" will have to help me out here.

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Chuck Rivers, Webmaster

The two most common problems with the 7 1/4 are the axle bearings and the spider gears.

Axle bearings are hard to check without pulling the axle shafts. If you are going to pull them. I typically have some extra axles serviced with new bearings and just swap them in. These bearings are not that expensive, figure $40 per bearing the another $30 to $40 to have them pressed on the axle.

To check the spider gears you need to pop off the rear housing cover. Get a new cover gasket and 2 quarts of new oil and go at it.

Once the cover is off you can easily see any chipping or worn-out gear surfaces. If the spider gears are going bad, then you should look for a good used replacement rear end to swap in, just because that should be a cheaper fix the rebuilding the current unit. (Your rear can be "patch repaired" pretty cheap if you know how to work on these things.)
DD

Dude! You're in Sunnyvale? I live in Sunnyvale too! Where's your shop? Maybe I can show it to you.

What part of Sunnyvale, CA? What year is your Duster? Are you sure it has a 7 1/4 rear end under it?

I do not have a shop but I do have some extra parts, like some good used axle shafts with decent bearings, that could be your "easy fix".

I still think you should take off the cover for a look at the gears.

I live by Arques and Lawrence. I'm still driving this car around, so if you're somewhere in Sunnyvale, it's no problem for me to drive the Duster over so that I could show it to you. Yeah man, it's a small world! I was really surprised when I saw that when you were in Sunnyvale too! I'm not sure if the rear is a 7 1/4. How can I tell for sure?

I'm not very confident about taking off the rear housing cover. The manual I have is the CD version, and it's kind of confusing. How many bolts do I have to take off? Where exactly are they located? Do I need any special tools?

I'm going to take off the rear tires and see if the brake is causing the noise, but I very much doubt it. Still, it's better than sitting around here doing nothing.

Here is a (bad!) shot of the 7 1/4 rear axle. If you see this cover, it is a 7 1/4. Remove the bolts on this cover.

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Chuck Rivers, Webmaster

Thanks for uploading that pic, Chuck. I got under my Duster and took these pics of her rear end. Don't get any perverted thoughts. The rear end looks pretty similar, but I'm not sure if it looks similar enough, because I haven't peeked at the rear ends of other 6s. Is this the same rear end?



Also. here's a stupid question. When the mechanic unbolted the butt-plug of the rear end to see if there were any fluids in it, he referred to it as gear oil. Is this the same as the car oil that you pour into the crankcase when doing an oil change? After I've inspected the inside of her rear-end, do I just add more oil to the crankcase or do I have to put it in there before I bolt it up?

It's the same rear. When you remove the cover, all the gear oil will spill out, so have a drain pan in place. You need to replace the fluid with a "hypoid" gear oil, not engine oil. Engine oil will not properly lubricate hypoid gears. You put the oil in after the cover is installed. You will need some kind of pump to get the oil into that plug (fill hole). Sta Lube sells the oil in a quart container with a pump on it (available at most auto stores). Fill 'er up to the bottom of the fill hole.

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Chuck Rivers, Webmaster

We opened up the rear and looked inside. There appeared to be nothing wrong with the gears. We filled it up to the bottom of the filler hole, before we reinserted the butt plug. But we did that with its fanny hanging high up in the air, because we jacked up the rear to get under it. So we probably put in a little more gear oil then we should have. Is that ok? Also, when we bought the gasket, we forgot to get gasket sealant. Is it ok if we didn't use gasket sealant? I noticed that when we spun the right tire, the gears inside would spin fine, but when we spun the left tire, when the gears spun they didn't always seem to be in sync with the left tire, which is the side where we hear the noise. What's the next step in finding out where this noise is coming from?

If the unit is not leaking then you did fine, no sealer is needed on the gasket if you get the surfaces clean.

How did the old oil look? nice and clean. no metal flakes?

Next stop are the Axle Bearings, the left side goes out first just because of all the right hand on-off ramps we have in the states.
What year is this car?
DD

The oil didn't look the same as the oil I put in. It was a dark brown, like the oil that comes out of the car when you do an oil change. But I didn't see any metal flakes.

The year of the car is 1970. How do I check if it's the axle bearings?

A quick check is to jack the car up and push the tire in & out, there should not be any "play" or looseness. Real bad bearings will feel rough when you spin the wheel and even have some up-down play.

For a real accurate check, pull out the axle shafts and rotate the bearings by hand to see how good it is. The best thing is to have some spare axles serviced with new bearing and just swap them into the car seeing you are in there. (I have some extra shafts if you want to do this)
DD

I have never worked on the rear end of my valiant so I'm kind of new to this part of the car.

Upgrading the rear end is going to be part of my next project on the Valiant. (I'm still doing the paint. Will it NEVER end????)

Anyway, I was wondering about that wire the mechanic was pulling on. Could that have been your parking brake cable? And if he was pulling on that right next to the wheel as it is spinning, wouldn't it change the speed of the wheel next to where he was pulling on it?

Have you pulled the drums off of your rear brakes to have a look at what is inside?

Of course I could be totally off here.

John

I already tested the wheel for looseness. It is about as stiff as the tire on the other side, and the other tire isn't making any noise.

I would like to pull out the axle shafts to inspect them, but I've never done it before. The closest thing I've done to this is change CV axles. The farthest I've been on this car in that area is removing the wheels. After that I don't know what to do. After you remove the wheels, then what do you do? Do you have to remove the brakes?

Chuck said that the wire the mechanic was pulling on was the parking brake cable, and I believe him. If I remember correctly, there were two wires. One time when he pulled it I remember that one wheel stopped and the other spun, but if I remember correctly the first time he pulled on the wires all it did was cause the driver side rear wheel to spin at the same speed as the other tire.

I haven't pulled off the drums to see what's inside. First of all, I don't know how, and then even if I did get it off, I wouldn't know what to look for. I've replaced disc brakes and removed drum brakes before, but those were on front-wheel drive cars and that was a long time ago.

I think what I need is a shop manual. The one I've got is on CD and I can't even print out the pages. Does anyone know where I can get a shop manual real quick? I don't think I have time to order one on-line. I want to have this car ready for another long trip I'm going to take on Friday.