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Discussion Starter #1
This is my 93 5.0 Bird, with under 95,000 miles on it. I recently started hearing what I can only describe as a fine tooth grinding coming from the rear of my car when attempting to move in reverse. It doesn't do this all the time, and there's nothing in particular that changes when it does it. I've checked all the brake hardware, and from the best I can tell, the axles appear to be seated in firmly, but this is still coming up. It does not do it in forward motion, no matter how hard i step on it. The car will move in reverse, but continues to make this noise. Any thoughts. I know I can drain the rear diff and look at the fluid, but if I do that, I'd like to have some thoughts once I get down there.

Thanks!
 

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Here's my thoughts on that, if you're positive the noise comes from the rear.

Brakes dragging. Sounds crazy, but I've had that happen before. And it only did it in Reverse! New shoes/pads and drums/rotors made it all go away.

Pinion gear bushings severely worn or misadjusted. Now, I'm not sure about the Ford 8.8 rear setup as far as it having crush-to-spec pinion bushings or what... but if it's discombooberated it could allow the pinion gear to physically move fore and aft and cause the gear mesh to get way off. Explains why it does it only in Reverse. My Roadrunner had the crush-to-spec pinion bushing and when it wore out you could actually see the driveshaft move fore and aft depending on which way you turned the tires by hand when the rear tires were off the ground. Made a horrid noise in Reverse.

Some of this you may have thought of and already checked. But it's difficult to "go by ear" when you just can't hang underneath the car and find the exact problem while going down the road like that one commercial shows.....yeah. Don't try that.
 

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Discussion Starter #3
Well I will recheck the braking stuff again, it's about time to replace the drums and all that anyway, so "go cheap stuff." Since this has started, I've had a pretty bad vibration and shimmy, so the brakes have been prime suspect up to this point, but when I heard the grinding it caused me to doubt myself just a bit. I'll take a look at it and post back.
 

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The "vibration and shimmy" part along with the grinding would lead me closer to the drivetrain parts than the brake parts. Unless that vibe n shimmy only happened when braking, of course.

Can you get the rear tires off the ground (only one tire if you don't have Trak Loc) and turn a tire by hand back and forth to see if you can see or hear anything happening?
 

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Discussion Starter #5
Here's something that I forgot, this grinding also happens when I downshift, as in, if I'm cruising in OD, and drop to D, it can do it, again not always, but it's happening. Here's something else. When I was doing the brake work, if I rotate a tire forward, it stops as one would expect it to, but if I rotate it to the reverse, when it stops, it makes a low thud unlike the stop to the forward motion. I do have a vibration when I apply the brakes, I think I'm needing to re-bleed the brakes for that, because it's not always there. If I am coming to a stop from a high RPM run, I tend to have no vibration, but if it's just a highway cruise, and I hit the brakes, I feel it all over. I guess we'll see soon enough. I'll probably wait to hear back on here before I go too much further.

Thanks again for the input.
 

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Discussion Starter #6
Any ideas, I know it's been a while, but I still haven't been able to pinpoint this yet. More drive time has given me this.
1. During solid acceleration, no vibration, usually causes the vibration to stop if I accelerate harder.
2. (Possibly unrelated) I do have a vibration in braking, but it goes away after hard acceleration. Example, say I'm coming up a hill, and I mash it, running high RPM's and have to hit the brakes, they will be solid and smooth. Cruise a while, and push them, and it's wobble time. BAD!
3. I think the squeaking sound that I was hearing the resembles grinding at times, could be one of the springs in my rear drum, I'll isolate this soon, but the clunk and slop has me concerned.
4 Lastly, it feels as though the drivetrain is sloppy. If I'm slowing down, just coasting letting the engine do the work and hit the gas, there's a large thud, like a sloppy joint, but each time I check the Ujoints they are solid.

So if any of that helps narrow this down, I would much appreciate the input. I'm getting near the end of the driving season for this car, since winter will awaken the 79 Bronco for snow play, but I still want to make this right.

Thanks for reading the novel.

Scott
 

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Put the car up so you can rotate the rear wheels, and have someone hold one of them, while you turn the other one with the vehicle in park.

Look closely at the u-joints, and the crimped sections of driveshaft itself. Look for play or movement. Mine had one bearing of a ujoint bad.

The driveshaft is two pieces, and it can come apart. Mine rattled when I replaced it...scary.

It also took out the rear end gears and the transmission tailshaft bushing.

Search for vibration problems; you'll see this is a fairly common thing.
 

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Scott,

Did you find the problem? Sounds like the problem I had, bad Pinion Bearing.
 
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