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Whining or grinding when coasting


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07 AWD makes a grinding or scraping noise when coasting in gear or neutral, but goes away under acceleration. Brakes are new, bearings are new, transmission is about 35k old. Can be heard best on passenger side. Tires all match and have the same amount of wear. I'm at a loss.

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How many miles on your Edge? Is the noise continuous or intermittent when coasting? Is it only when you start up it up and drive away after letting it sit for some time?

 

AWD immediately begs the question: PTU. So check the PTU fluid condition, see if there are any signs of leaks on the unit or the driveway. With your foot on the brake, work slowly through the gears and listen carefully to see if you can hear it while the Edge is not moving.

 

Did you install the brakes yourself (rotors AND pads, or just pads or ...)? Are the caliper slide pins and pistons moving freely?

 

Is the transmission that was installed new/recertified/used?

 

Check all nuts & bolts on the parts replaced to make sure everything is mounted properly & securely. May have to use loctite to secure those that have come loose.

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I would start by jacking it up and giving everything a go over then spinning the wheel etc. Sometimes drive train noise can transmit them selves from on location to another so this also makes diagnosis a difficult situation. Being AWD PTU is always suspect. It could also be bearings on the drive line to the rear. This drive line is either a two or three piece so you may want to check that out also.

 

Grinding as a note will generally be more pronounced from brakes that have been sitting even from an overnight rest.

 

Not sure how many miles you have the NEW bearings, but I have had a bearing fail with just 20k miles on it.

 

Brakes is stuck can wear quickly down to metal and grind also, usually a front or rear catch will cause one end to stick and wear down to metal so check the pads. You should be able to do this inspection with flash light and removing the tires and some real close viewing.

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Replaced both front bearings about 8k ago and the passenger rear on July 30th, brakes are about 500mi old, yes I did them myself and I put high temp grease on the guide studs. Also did the bearings myself. I read on one of these threads that although the PTU claims zero maintenance that the oil often breaks down at high mileage and leads to PTU failure. It doesn't leak anywhere but I'd like to drain and refill it, but I'm not sure how or what kind of oil it uses.

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Wow that was a very helpful write up on that link. I tried to hand pump out the old oil but can't get the suction hose past the gear into the bottom. The little bit I got out was still runny by definitely saturated with metal filings so I hope it's salvageable. I think that adding the drain plug on the bottom is the way to go.

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Do drain & fills at short intervals initially. As it thins out with each fill, should be easier to pump out more. Measure how much you are putting back in each time, if you can get the stated capacity out, that'd be perfect!

 

You do have to use a flexible hose to get to the bottom. Like these kits:

http://amzn.com/B000CMDPBM

http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_x_22973737-P_x_x

http://www.amazon.com/dp/B006AZKBO4

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