Moan at between 35-40 MPH

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killnine

killnine

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So I just got my 'used' 8.75 rear end installed, along with the cut driveshaft. I'm getting a low frequency moan between 35-40 MPH. Doesn't seem to matter if I'm accelerating, or decelerating, it will happen in that range. There is no vibration that I can feel, it remains as smooth as usual as far as I can tell. The rear is used but said to be 'good', but I don't have any information to confirm that. I put new custom axles in it, filled it with fluid that has additive already in it, and ran it. Does this sound like a rear end issue? Any advice?

I should add that the moan is not loud, just like a constant low frequency sound that is loud enough to notice for sure, but not like a bad bearing or something would usually be. It almost sounds like some tires do on certain roads.

Thanks
Alex
 
Get louder exhaust! :D Are you running green bearings or tapered roller on the axles?
 
Alex I have no idea but my wife used to moan when she was younger but that pretty much stopped before she hit 35. Dan
 
Ugh yenz guys... Aaaaaanyhow, the axles are new from dr. diff, green bearings. the housing and pumpkin are used. it's a sure grip cone style, 3:23. I used the royal purple gear oil that says it already has additive in it for the sure grip. I do have some actual chrysler additive for it but didn't think it was necessary.
 
Try some 85w140 with ford FM. Most likely it's the gear and will have to live with it.
 
I could hear the 2.94s in my Dart till I put the new pipes on. It may be able to be adjusted out and it may not. You really need to see the mesh pattern to tell. Have you felt the slack (back lash) by hand?
 
Mine made noise anytime past half throttle, no matter what speed. I quit taking my wife with me. Noise stopped.

:eek:ops:
 
I dunno I just went for a drive again and now it seems to happen all over the range of speed. It also seemed to get louder going into the throttle, and softer coming out of it, but sometimes not. When it is moaning it doesn't always matter whether I am on the throttle at all, it will still do it just coasting, decelerating, or anything. Anyhow, I think I need to take more notes and define the issue better. It may be just something to live with until I actually open the rear up and do something about it. If it were a driveline angle issue I would assume I would get some kind of vibes and not a moan.
 
If it is changing as you drive it.... I would pull the pumpkin and check EVERYTHING. Preload on the carrier bearings, torque on the bearing caps, wear pattern and backlash, preload on the pinion bearings etc. If it has just started or is not quite set up right you can probably cure it. Once a gear set wears in to a noisy pattern it is usually there for the life of the gear set.
 
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