Focus0828

Hi all, I have a noise coming from the rear end of my Mustang. I seen a lot of threads that mostly reference a groaning sounds from the rear end but I have not seen on that really describes the sounds I'm hearing. It's a hi pitched wine I only hear when I'm pulling off from slows speeds when the car is cold but seems to go away at about 20-25mph when cold and not at all once warm. I recorded the sounds and posted it on youtube for users to hear. If anyone can help out it would be much appreciated. I took it to a local shop who said it sounds like the gears in the differential could be whats wrong but I wanted to check the forum so see if anyone would agree. Thanks.

imp

First, high-pitched whine can be either pinion gear bearings (not the gear itself), or gear-tooth noise originating with ring and pinion teeth themselves. From what i'm hearing, the sound is not pitched to coincide with gear OR bearing noise, but rather sounds like low-pitched rumble of road noise. Can you answer this: does the noise change at all if you enter into a curved direction (turn) while it's happening? That would indicate differential gear trouble. There are 6 gears in most rear axles (8 in 4-pinion differentials), so noise can be hard to identify. imp

Focus0828

No the noise is pretty consistent no matter if I am turning or driving straight but once I go over 20 or 25mph it slowly goes away. I will double check when I have to drive this evening but I hear no change when turning. The shop I took it to said it sounds like the differential and then quoted me over $1200 to replace the gears which caused me to pause and look for 2nd opinions.

Urambo Tauro

Did the shop put it on a lift to inspect it before giving you a quote? Whatever it is, sounds pretty dry. Could be in the axle, but I can't be sure from where I'm sitting. For all I know, it could be coming from the driveshaft.

Focus0828

The shop said they put it up and turned the diff manually and heard no sound but when the put it all back together the sound is there when pulling off. After the shop the sound went away for about a week and came back a few days ago.

Urambo Tauro

Hm. Well putting the car up on the lift would do a couple of things. For one, the axle would droop, changing the driveshaft angle a little bit. It would also take the weight off of the axle bearings...

Focus0828

Agreed. Which makes it hard to tell based on their description knowing the full load wasn't on there when they tested it. If it is the axle then I don't think it would stop after driving until the car is heated up.

imp

If it's a frame-contact lift, not an under-tire lift, of course. I have very often found that hand-moving of driveline parts often fails to reveal the noise at all, unless U-Joints are about to fall apart.......or REALLY bad bearings are present in the center section, in which case the noise is so bad, only a half-wit would drive it. imp

Focus0828

I'm thinking it may be the axle. I paid close attention to the noise yesterday and today. It does not change during turns. It definitely coincides the rotation of the axle turning or straight. I may just start with the bearings before I think of replacing the entire axle. I just wanna get it done because this issue is going to cut into my new Stayfast top install funds lol. From what I gather and correct me if I'm wrong but the diff noises usually change when turning compared to driving straight

Urambo Tauro

I dunno about "usually". There are different ways in which the rear end can fail, and there are different noises that the axle can make under different conditions. Barring any out-of-the-ordinary abuse, I would imagine that typically, pinion bearings would probably be the first to exhibit signs of wear, followed by wheel bearings.

Since your noise doesn't seem to change with turning, I wouldn't expect the differential portion of the axle to be at fault. Upon listening to your video again, I stand by my suspicion that is sounds very dry. So unless there is a foreign object coming into contact with a rotating part (like a bent brake dust shield or something), it would seem that something has lost its grease or oil. Could be an old U-joint, or an oil-starved bearing... Have you checked the axle oil level?