Need Help with Rear End Problem on my 70 Mustang

[blk66stang]

I have problem that I need help with.

I have a 70 Mustang sportsroof that I am trying to bring back to life. I have it running, steering, shifting and stopping. The problem that I am having is in the rear end (somewhere).

I have only driven up and down the driveway. At the same spot when I back up there is a feel and sound that comes from the back end. It almost feels and sounds like something is binding up and then releasing. It is bad enough that I can actually feel it in the drivers seat. I had my two neighbors watch while I backed up and pulled forward. One of them thinks it is in the rear end. The other thinks it is in the rear, passenger side wheel (he thinks that the rear, passenger side wheel actually moved when it happens).

Here is some additional information:

1. Rear end is out of another model of Ford. The tag is "WDZ-8(or B?)1(or I?) 9EB 3L00 8 875A". So it is an 8" posi out of ? Fairlane?
2. The parking brake cables are not connected to anything (they are both hanging down).
3. When I apply the brakes and come to a stop the car rocks back and forth a little.
4. I raised the rear end up and turned the rear tires in both directions. They were hard to turn. And in certain spots (every 3rd full turn or so) they were very very hard to turn. Both tires turned together in the same direction. There was no play in the driver side tire. There however was about 1 1/2" of play in the passenger side tire. What I mean by that is when I turned the tire it turned about 1 1/2" before the axle engaged and the drive shaft turned. And when I turned the driver side tire the axle would turn and the drive shaft would turn immediately but the passenger side tire would not turn until the driver side tire had turned about 1 1/2".
5. The drive shaft and rear U-joint seem to be solid with no movement in /out, up / down or side / side.
6. I took the wheels off. The brake drums don't match. They have the same width and height dimensions but the profile is different. The hole in the passenger side drum that the axle hub sticks thru is also 5/16" bigger in diameter that the hub. So even though the lug holes are correct (correct pattern), the hub hole is not and the drum is loose.
7. I took the brake drums off. The brake components seem to all be there and installed correctly. The brake shoe adjusting device on the passenger side was not competely slid into the indented slot on the brake shoe. I just simply slid it back into position.
8. When I pulled on the end of each axle they did not move in / out or seem loose.

I think that is all I know. If there is something else that would help someone figure out the problem, just let me know.

Thanks.

 

[blk66stang]

I might add that the rear passenger side brake has fluid on it (from the cylinder I am guessing). I didn't know if that would make a difference in trying to figure out what is wrong.

Also, my driveway is sloped. So when I am backing up, I am applying the brakes. And when I am pulling forward, I am accelerating. I do not remember feeling / hearing anything when I pull forward, just when I am backing up.

And last, the car sat for 3 years before I purchased it last spring.

Thanks.

 

[70vert]

first amateur reply

6. I took the wheels off. The brake drums don't match. They have the same width and height dimensions but the profile is different. The hole in the passenger side drum that the axle hub sticks thru is also 5/16" bigger in diameter that the hub. So even though the lug holes are correct (correct pattern), the hub hole is not and the drum is loose.

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The passenger side drum is actually moving and hitting the drum pads every third revolution or so? The hat, or drum, in this case, needs to fit exactly over the hub. If you have an open diff, only the passenger side breaks free, so that might explain why the brake drum applying on the passenger side every third revolution would bind up the driver's side too.

 

[hotcobra03]

I would pull driveshaft out and check for a frozen ujoint.buy jacking up rear you found wheels spin .when u drive in driveway shaft spins say 4 to 1 and you wheel turns once every 5ft.

 

[ultrastang]

1. Rear end is out of another model of Ford. The tag is "WDZ-8(or B?)1(or I?) 9EB 3L00 8 875A". So it is an 8" posi out of ? Fairlane?
Thanks.

By the "3L00" from the tag, I see that you have a Limited-Slip differential. It may be as simple a problem as the discs in the differential are binding up. When they do, and then suddenly release, it will make a loud clunk/pop and make the whole car shudder. I would suggest getting a 4-ounce bottle of Friction Modifier from the Ford dealer and pour it into the rear end.

Make (5) tight left hand turns followed by (5) tight right hand turns. This will help work the Friction Modifier in between the friction discs to free them up from binding.

IF this is your problem, the Friction Modifier should start fixing the problem fairly quickly. If it persists, then obviously there is a more serious problem, but this would be the simplest, cheapest and easiest route to take now to see if the problem goes away.

 

[blk66stang]

Thanks everybody. You have given me a few things to check out and do. I will let you know what the results are. Thanks again.

 

[hotcobra03]

For clutchs in rear,wouldnt you need to be driving car to feel it binding?how long is his driveway?i say unless his rear tires arent way off in size ,i go 4 frozen ujoint.

 

[ultrastang]

For clutchs in rear,wouldnt you need to be driving car to feel it binding?how long is his driveway?i say unless his rear tires arent way off in size ,i go 4 frozen ujoint.

In the late '90s, I had a '57 model Ford station wagon 9-inch rear with a later 3.70:1 Traction-Lok [from a '75 Ford pickup] under my '68. The engine was out of my '68 at the time, but just with me pushing the car around in the shop, the differential clutches would pop because there was no Friction modifier in the rear end.

This may not be the problem for the original poster, but then again, it may be. It's much simpler and cheaper to take a chance on putting a 4 ounce bottle of Friction Modifier in the rear end to see if that fixes the problem, first, rather than changing U-joints, etc.

If it doesn't fix it, then I would look at other more involved, more costly solutions towards tracking down the problem. If it does fix the problem, then the original poster has not spent a lot of time, effort and expense on things that did not need changing.

 

[blk66stang]

I measured the tire circumference and it is roughly 6'-8". When I backed the car up, I went about 25' before it popped. I went maybe another 10' before I stopped at the end of the driveway. Then I would pull forward back to the garage. I repeated this several times and the pop happened at roughly the same spot each time when I was backing up.

 

[hotcobra03]

Not saying change ujoints but unbolt it and ck 4 binding .orange rust near grease seals is a good sign.pushing up and down on shaft will be checking for a loose ujoint. a frozen or binding ujoint can only be found with shaft in hand.

 

[blk66stang]

Adding friction modifier and checking for a frozen u-joint both seem like easy "first step" thing to do.

Can you give me a little more information about a "frozen" or "binding" u-joint? What specifically am I doing to check the u-joint? I am going to unbolt the u-joint and remove the axle from the flange. Then what?

 

[hotcobra03]

With shaft in hand move trans slip yoke both ways it should move freely same on rear ujoint .very easy to do