I have 59k on my 2012 Expedition and took it in for servicing: new spark plugs, heater hose, tires, front/back brakes and struts. Wife heard an intermitted hum when accelerating and requested this be looked at during the servicing. The hum does go away once the truck warms up. Firestone said this was a transmission problem so we took it to a reputable transmission shop on Tuesday March 27th, to have it looked at. After driving the vehicle, connecting it to the computer and putting it up on a rack for inspection, the service tech came back with a clean bill of health. We took it back to Firestone on Friday March 30th to complete the spark plug and hose install and when we left, it sounded like the muffler was dragging on the ground. Total grinding noise. The noise would go away when we took our foot off the accelerator. We took it back the next day and the service tech said that it was a transmission/differential issue. How can the transmission/differential go from good to sounding like we are grinding the gears? We have an appointment for a second opinion tomorrow (Monday April 2nd). When the Firestone Service Tech put the truck up on the rack, in 4-wheel drive and accelerated, the wheels on the driver's side were not going the same speed as the passenger side. Probably about 1/4 the speed. Any thoughts as to what could be wrong or is this typical for this vehicle?
2012 Expedition Transmission/Differential Issues
- Thread starter Timm
- Start date
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AllBoostNoEco
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The transmission and differential are completely different components. If they said the transmission is fine, then it could be a differential or transfer case problem. A hum that’s turned into a grinding noise could be a variety of things, bad spider gears, bad pinion bearing, even a bad CV joint.
The wheels turning different speeds doesn’t necessarily mean anything, the truck has open differentials, so they can all go completely different speeds without issue. Without load, in 4WD, generally power goes primarily to the driver front and passenger rear tires, but that could be the computer for the stability control trying to figure things out.
A differential or transfer case failure at such low mileage would be highly unusual. Doesn't mean it can’t happen, just would be atypical.
Is the hum/grinding noise dependent on the gas pedal being pressed solely, or does it also change with vehicle speed? Symptoms existed in 2WD? And was it making the noise when it was on the rack in 4WD? Is there any play in the pinion?
The wheels turning different speeds doesn’t necessarily mean anything, the truck has open differentials, so they can all go completely different speeds without issue. Without load, in 4WD, generally power goes primarily to the driver front and passenger rear tires, but that could be the computer for the stability control trying to figure things out.
A differential or transfer case failure at such low mileage would be highly unusual. Doesn't mean it can’t happen, just would be atypical.
Is the hum/grinding noise dependent on the gas pedal being pressed solely, or does it also change with vehicle speed? Symptoms existed in 2WD? And was it making the noise when it was on the rack in 4WD? Is there any play in the pinion?
The CV Joints were good. To answer your questions: The hum/grinding noise is solely when the gas pedal is being depressed. The symptoms exist in 2WD and 4WD. Yes, the symptoms existed in when it was in the rack however; no where close to the sound it made when it was under load. There wasn't any play in the pinion.
AllBoostNoEco
Full Access Members
Sounds like a rear diff problem based on what you’re saying. I’d see if there is any grinding with the rear wheels off the ground and turning one by hand. If you feel any resistance or grinding then that narrows it down to the diff bearings or the spider gears. If it feels really rough, one of the spider gears may have broken and there are chunks floating around.
I wasn't able to turn the wheels while it was off the ground. If it were chunks of the spider gear floating around, wouldn't I hear that noise whether I was accelerating or foot off the pedal? Does the spider gear stop turning when I release the accelerator? Do you know what an estimated repair cost would be for something like this? I want to know just in case the estimate given to me sounds a little high! LOL Thank you.
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