Nasty differential noise?

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someguy

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I have a 1990 Bronco XLT with a 5.8 and E4OD that is making a very bad noise from the rear end.  It's a FAST rhythmic thumping/grinding, that screeches when it stops.  I had it re-geared to 4.56 gears a few months back, and right after the gears were done it buzzed when  you let off the gas at highway speed.  I checked the brakes and wheel bearings, and I'm pretty sure the sound is coming from the rear end, but when I took it back to the shop, they assured me that they pulled it apart and the gears were fine.  They told me it had to be the driveshaft, which makes sense because it was stock and the Bronco was actually on an ~8" lift when I bought it.  Problem is, I replaced the driveshaft, and the noise is still there. 

Here's my question, when I pulled the driveshaft, I spun the pinion yoke by hand, and it rotated quite a bit, around 1/2-3/4" inch in both directions.  I'm wondering if the tranny shop was just trying to get me out the door, and there actually is excessive backlash.  Here's a video of the yoke spinning, please tell me if this is right or not, and if it isn't the differential, if you have any ideas:

http://tinypic.com/player.php?v=nwj5ug&s=9#.WAfECv0zW2w

 

Seabronc

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No that doesn't look good, looks like the pinion is not properly seated.  I wonder if they used all new hardware when installing the pinion.

:)>-

 
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someguy

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Thanks for the help.  I wanted a second opinion before I went back to this guy again, it's good to know I'm not crazy.  And yes, I gave them a Ford install kit and paid for additional new hardware on the install. 

The transmission shop is County Transmission in Vienna, VA.  Not sure if anyone might have experience with them, but they seemed legitimate until they  told the problem was the driveshaft and the differential was fine. 

 
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Bully Bob

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There is a certain amount of play as I recall. 

While you're there.., have them put it up on the lift & run it. Easier to spot the noise.

It's possible the issue is in the transfer case output shaft.

 
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someguy

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There is a certain amount of play as I recall. 

While you're there.., have them put it up on the lift & run it. Easier to spot the noise.

It's possible the issue is in the transfer case output shaft.
Thanks, maybe I should check the transfer case as well. 

I brought it to the tranny shop last week, and they said they checked it and told me the problem was in the driveshaft.  Assuming they were being honest and the differential is fine, since the problem isn't in the driveshaft, then the transfer case would be the next step up the drive line.  That said, the sound really seems to be coming from further back. 

 

Bully Bob

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U-joints are the only thing on a dr. shaft that move & even then, not a whole lot.

Then there's the slip joint.., not likely going to make that noise.  (don't know why they blamed the dr. shaft)

Noises have a habit of "throwing their voice" 

They should have insp. the wheel bearings as well, when they pulled the axles.

If they're sealed bearings., they can fool you.  A problem may not show up 'til they're warmed up.

Up on the rack.., they should be able to find & show you where the problem is.

 
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someguy

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I still say that the pinion is not set right, take a look at this http://broncozone.com/topic/12256-88-pinion-bearing-pre-load-adjustment-video/

:)>-
You may be right, I showed the video to the tranny shop and they said to bring it back and drop it off.  The guy admitted he hadn't inspected it himself, sounded like they didn't really check the backlash when they had it.  A bit frustrating, considering the shop is 25 miles away and closes promptly at 5:00, and I've already burned half a day of work picking it up last week. 

 
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someguy

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OK second really stupid question:

If I need to get this thing to the shop 25 miles away, and the diff seems to be making noise, can I drop the rear drive shaft entirely and drive it "front wheel drive"-style in 4x4 high to the shop?  I'm thinking side roads and <35mph...

 

kenh

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OK to use front axle only.

Back in the day I did so with a 3/4 ton GMC, kept speeds down to 65MPH

 
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someguy

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OK, quick update on this if anyone else has the same problem.  The problem actually was the transfer case, and Bully Bob was right in that it just sounded like it was coming from the rear end.  Took off the rear driveshaft and it still made the exact same noise in 4WD, so clearly not the differential or rear driveshaft.   

To give you an idea of how bad I am at this, it took me all this work to figure out I had a slow leak in the transfer case.  Apparently, when the Borg 1356 fluid gets too low, it makes that rhythmic sound.  I added a full quart of the Motorcraft transfer case fluid before it was full, and then it ran just fine.  I'm left wondering if I did any damage driving it before it got benched, but it works now.

 
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Bully Bob

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Good, and thanks for the up-date. 

"I'm left wondering if I did any damage driving it before it got benched, but it works now."

However.., what do you mean by "got benched"..? Did you remove the transfer..?

Not likely any damage but it wouldn't hurt to give it a complete drain & re-fill if not already done.

P.S. removing the dr. shaft--- the rear end still spins.., just won't have a load on it.

In some cases, a noise will still remain.

 

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