Noise at high speed, looking for thoughts

[FordTaurus]

Hi all, My Freestyle Limited AWD has been getting noisy at speed for a few years. Recently got more obvious than before.

At idle, no noise or helicopter noise. Shift to R and D no noise, same as always. Drive it under 30mph complete quiet. A bit noise starts at 30 mph. Then from 55 to 70 got very noticeable. It is sounding like there is a small extra motor running. Constant at high speed, quieting down with slowering speed.

I got my mechanic replaced both front wheel bearings yesterday, but the same noise did not go away. Obviously the mechanic mis-diagnosing the source of the noise.

I am thinking next is to have the rear wheel bearings just check up.

Hope someone can give me some input. Thank you!

I just have done the 100,000 trans service, replaced both front brake pads and accessories drive belt.

[Thrusty]

Generally, you can usually rule out wheel bearings by making some hard turns at speed. The noise will get quiet or disappear turning one way and get noisier turning the other way. The side you are turning away from would be the suspect side.

Also maybe inspect the tires carefully and look for odd damage or separation. Could also try rotating them to see if that changes anything. (I've seen it before in my life).

Those two things are free and easy. I suppose next if it were me I'd inspect the fluids on the PTU, differential, and AWD unit.

[Thrusty]

Oh, you haven't recently added any roof racks or cross bars have you?? With my crap brand cross bars Installed it sounds exactly like bad wheel bearings over 40mph, ugh.

[FordTaurus]

Thanks so much for your response!

I have no roof racks, no oil seen on the floor yet, noise on highway constant not change by changing directions, no error code showing on dash.

I am trying to drive it until very loud and or problem arises. Then decide repair or replace vehicle.

Should I have my Ford dealer diagnoses pin point the problem now or later, they charge $100 for diagnostic?

Should I drive slower to lesser the extend of damage?

[FordTaurus]

Talked to the mechanic on the phone he said he knew where are the problem. Both sides at the rear but not bearings. He said he will point to me when I bring my car in. I will go to see him the next day.

Searching on the internet, more and more felt like rear differential.

I wonder, will an oil and filter change for the differential now, quiet down the unit. Or too late?

[Webmaster]

Maybe your PTU is shot. If it overheats at any time it's life is shortened.

[FordTaurus]

Maybe your PTU is shot. If it overheats at any time it's life is shortened.

Thank you, I see that road ahead !

[FreeStyleNole96]

What is the PTU?

[Webmaster]

What is the PTU?

Power Transfer Unit, basically it's a transfer case for AWD vehicles.

[Thrusty]

Well, it can't overheat. It's just a gear set. I suppose they could wear and cause noise but, heat is no isssue.

[Thrusty]

The car can be ran without the PTU in place, and that's a (the) procedure for noise diagnosis in that area according to the shop manual (sorry no reference handy) but I can't imagine it's simple to pull the PTU and put the half shafts back in there... well, simple maybe but time consuming not likely.

[Webmaster]

Well, it can't overheat. It's just a gear set. I suppose they could wear and cause noise but, heat is no isssue.

Heat is the main reason the PTUs die. The fluid overheats and/or pukes out the vent hole and takes out bearings. Well documented online, there is also a good video on YouTube about these things.

[Webmaster]

Should I have my Ford dealer diagnoses pin point the problem now or later, they charge $100 for diagnostic?

If it's only $100 that's a good deal. The hourly rate around these parts last time I checked was $125 and that was like 3-4 years ago so it's probably higher now.

For that price it would be worth it in my opinion to have a dealer do a proper diagnosis and then you'll know what the problem is exactly and how urgent the repair is.

Diagnosis via the Internet it is of course hard to do properly

[mmsstar]

Well, it can't overheat. It's just a gear set. I suppose they could wear and cause noise but, heat is no isssue.

The PTU can overheat! In fact that is what causes the fluid to fail which in turn will cause the gears to fail.
The seal can also leak and you loose enough fluid the gears will fail.

The information below was shared on the Flex forum by a Ford insider.

Ford in fact added a drain plug to the PTU, and a dash warning light on the Police Intercepter vehicles so the fluid can be replaced when it has overheated due to "severe" service. Since the PTU casting is the same on all vehicles, they all get the drain plug now but only the PI versions get the dash warning. They also added a cooling option on the PTUs on the PI versions.

[FordTaurus]

Hi guys,

Didn't expect any further replies, so Thanks! Since my last post, the noise has grown by 1/3 at least. My worry is that it is sounding more, more like a transmission input shaft problem. Next Wednesday will be my scheduled oil change and diagnose the noise at my Ford dealer. I will let you know the result and cost of repair.

If it is the CVT problem, I am deciding to or not to get a new vehicle which will have the up to date tech.

I hope it's just the PTU. But let me ask, if it is having input shaft noise problem, will it broke down, stop in the middle of the highway with a fail-safe mode? Or it is just a noise, I have to only bear with the noise?