AWD does not work

Tiny
CONNOR_CURCIO2004
  • MEMBER
  • 2007 FORD ESCAPE
  • 3.0L
  • V6
  • 4WD
  • AUTOMATIC
  • 117,000 MILES
I have the vehicle listed above XLT model, with intelligent four-wheel-drive. For the last month any time the rear wheels engaged I would hear a loud banging noise and I didn’t think anything of it until one day during heavy rain the rear wheels engaged and then there was a loud bang and the four-wheel-drive light started flashing. Sometimes the light just stays on without flashing. Ever since then I have not had four-wheel-drive and just to be on the safe side I filled the rear differential with fluid but have still not been able to engage four-wheel-drive any ideas on what this is and how I can fix it. Thanks
Sunday, May 1st, 2022 AT 11:36 AM

6 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Your vehicle has what is called a torque coupling system. Basically, this means the vehicle is in 2WD until it is determined that 4WD is needed. At which point, the clutch is applied, and the driveshaft and rear diff are locked and you have 4WD.

If when this is engaged you hear noises, then most likely the clutch has failed.

However, first we need to find out if you replaced one, two, or three tires at a time and not all 4. On this vehicle you must replace all 4 tires at the same time otherwise you will cause damage to this system.

At this point we could have an issue with the rear differential and/or transfer case. So, we need to put the vehicle on jack stands and lock the 4WD system and see if you can pinpoint where the noise is coming from.

https://www.2carpros.com/articles/jack-up-and-lift-your-car-safely

Let's start with this and then that will determine what direction to go. If you are not sure if this is a PTU/transfer case or rear end, then you can unplug the rear coupling unit and see if it still makes the noise. If it does, then the rear diff is not the issue.
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Monday, May 2nd, 2022 AT 1:21 PM
Tiny
CONNOR_CURCIO2004
  • MEMBER
  • 4 POSTS
Thank you, that’s the most helpful information I’ve been able to find. But the 4wd doesn’t work at all, it’s like the rear end is paralyzed, after I heard that loud bang noise it just never worked again and it’s really annoying because now since all the power is going to the front wheels it breaks loose really easy, not going to lie I have a lead foot and I’ve really had to dial it back because I was smoking the tires 24/7, is there a chance I could have blown the rear differential because there’s something I forgot to mention. When I got the car, the rear differential had a small leak and I’m fairly convinced that it was running dry for at least a month and ironically that’s when it started making that loud bang noise.
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Monday, May 2nd, 2022 AT 6:31 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
So, the way to tell this is to lift the vehicle or in some other way tell if the drive shaft is spinning. If the drive shaft is spinning, then more than likely the PTU is not the issue, and the bang noise was the rear diff unit or the clutch. Either way, we need to check the tires. If you were spinning the wheels or driving hard then I bet, they are different circumferences even if they are the same size.

Different size tires are going to cause issues in this system so if you repair this then you need to have tires the same size.
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Monday, May 2nd, 2022 AT 6:56 PM
Tiny
CONNOR_CURCIO2004
  • MEMBER
  • 4 POSTS
Okay, again thank you for the helpful input, and I took a video with my phone under the car and saw that the drive shaft was spinning. And none of the tires are the same tread, but again when I got the car it was like that.
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Tuesday, May 3rd, 2022 AT 5:39 PM
Tiny
CONNOR_CURCIO2004
  • MEMBER
  • 4 POSTS
So if you were to take a guess what do you think is wrong and how should I got about fixing it?
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Tuesday, May 3rd, 2022 AT 5:40 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Based on experience with these units the most likely cause of this is the tires being different circumferences then it wore out the rear differential clutch and it finally failed.

They normally don't make a loud noise, which is normally the PTU but if the drive shaft is spinning and not making noise then it may be the rear diff is the only issue.

So, I suspect the rear diff needs to be replaced. However, before you make that repair, you need to replace all four tires, or you will start to damage the replacement parts as well.
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Wednesday, May 4th, 2022 AT 7:14 AM

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