Rearend noise.

[jumpervb]

Have a problem with my 2005 X.
Makes a noise when I first start out in it in the mornings or when its
been sitting for a while. More so when it is cold outside.
Sounds like a whomp,whomp,whomp that speeds up as speed increases
and then after a minute or so it goes away, I do think I've felt it but would not swear to it. Dealer says they cannot replicate it.
Any suggestions? I think It is coming from the rear of the X so I think it may be the gears.
Thanks!
P.S. I should add the rear end was reworked about a year ago because of the whine that you could hear around 60 to 70 MPH. It was a factory service notice not a recall but it was replaced free of charge.

 

[jumpervb]

Bump!
Can somebody give me some ideas?

 

[Ronin8002]

Parking brake maybe? Some people don't use theirs much and it deteriorates. Maybe it's dragging?

 

[ericautopart]

There's about 6000 threads on noisy 02+ diffs. Do a search and see if one of them replicated your issue.

 

[EasyRhino]

There's about 6000 threads on noisy 02+ diffs. Do a search and see if one of them replicated your issue.

I think the OP is talking a 2005.

Besides the noisy ring/pinions are a constant howl at highway speeds when you lift off the gas, and are not temperature sensitive.

I'm thinking something with a tire, wheel bearing, or CV joint, but I'm confused by the temperature effect.

 

[Gus Gorilla]

I think I've got it.
Tires can and will temporarily flatspot and cause just what you have. More pronounced in certain makes and/or quality of tires.
As you drive the materials flex, heat up, and it works itself out. Then you park it, the weight sits on one spot of the tire as the materials in the tread and sidewall cool to ambient temp. This causes it to retain the shape of when it is parked. One flat spot. But just for a bit, since the rolling of several thousand pound Explorers tends to work it back out again and the cycle repeats.
This is why it has to sit a while, why it's frequency change matches with speed, why it is more pronounced in cold weather, and why the dealer can't duplicate. If it really feels like the rear only then rotate your tires and re-evaluate for a week or two. If it moves and feels very pronounced in the front then you've got a crap tire or two. If it feels the same then it may be characteristic of your tires and just "seems" to be from the rear.

When cars are new on the lot it's recommended to drive them around every so many days. The tires can temporarily flat-spot. Then after a long enough time the brand new tires will permanently flat-spot.
I left a car sit for 3 months recently. I had to drive nearly 15 miles before the tires felt round again. Small car, cheap tires.

 

[EasyRhino]

I'll bet you're right.

 

[jumpervb]

I think I've got it.
Tires can and will temporarily flatspot and cause just what you have. More pronounced in certain makes and/or quality of tires.
As you drive the materials flex, heat up, and it works itself out. Then you park it, the weight sits on one spot of the tire as the materials in the tread and sidewall cool to ambient temp. This causes it to retain the shape of when it is parked. One flat spot. But just for a bit, since the rolling of several thousand pound Explorers tends to work it back out again and the cycle repeats.
This is why it has to sit a while, why it's frequency change matches with speed, why it is more pronounced in cold weather, and why the dealer can't duplicate. If it really feels like the rear only then rotate your tires and re-evaluate for a week or two. If it moves and feels very pronounced in the front then you've got a crap tire or two. If it feels the same then it may be characteristic of your tires and just "seems" to be from the rear.

When cars are new on the lot it's recommended to drive them around every so many days. The tires can temporarily flat-spot. Then after a long enough time the brand new tires will permanently flat-spot.
I left a car sit for 3 months recently. I had to drive nearly 15 miles before the tires felt round again. Small car, cheap tires.

I will try the rotation thing.
Went myself yesterday and drove it with the service manager and could not get it to do it again. So I guess I will just keep driving it and see what happens.... If it is a bearing or gears it will only get worse and more frequent. Bad part is that we have had a rental that I'm probably gonna have to pay for because they couldn't fix what wasn't broke. But they assure me that they believe me so maybe they will cut me some slack.