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2008 Ltd 4.6L intermittent front drive line noise.

pjw73nh

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08 LTD
2008 Ltd 4.6L 115k miles. Intermittent humming noise/fine vibration from front (feels like it might be right under drivers feet)

Just started with colder weather, but it's been warmer since and has not changed the sound. I don't think it's weather/temperature related.

Mostly at very slow speeds, only when turning left with slight load (IE making a slow left turn while on slight uphill incline). Definitely not engine noise.

I am thinking maybe transfer case/differential issue or perhaps U-joint(s). Both front wheel bearings are Timken and done within the last 20k. The sound does not sound like wheel bearing noise. It goes away completely after the turn is complete, or I speed up (above 5-10 MPH). Does not sound like CV joints either. Car rides beautifully all other times and speeds. No noises vibrations etc. Only happens on a slow left turn under very slight load. It is definitely increasing as time goes on.

If I put it in 4WD high, the noise is much more pronounced, easier to reproduce, and appears to happen at the same slower speeds, but on BOTH a right or left turn. Not just a left turn.

Any thoughts or help in diagnosing this much appreciated.

Thanks.
 


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Explorer_PL

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Front driveshaft - remove it, and see if the noise is still there. Half an hour job with proper tools.
 




pjw73nh

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Ex_PL, Thanks for the reply. I may not have the opportunity to do this until the weather gets less snowy and warmer in the spring. I believe my veh is an Auto 4WD, Has 4x4H 4X4L 4X4Auto.

Can I assume that this is an isolation procedure to rule out or rule in a particular area?

If the noise goes away, I can presume what?

1. That it is either the front portion of the transfer case (bearing?).?
2. The front drive shaft?
3. Something further into the front differential/CVshafts/joints?

Or is this simply isolating it to front or rear driveline?

Thanks.
 




Explorer_PL

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PJW-
I have dealt with 2 of those humming/vibration noises on mine (v8 as well). Both times I unnecessarily replaced hub bearings in the front since they were close to 100k so I thought no harm done, they are due soon anyway. I was wrong as usual :)
In my case, first time, it was the rear output bearing on the transfer case. I had some TC fluid drops around the seal. When I went under the car, I could physically grab the rear driveshaft and shake it around 1/8-1/4 of an inch on the front of it. Bought a used TC from a junk yard for $ 150 and it's been good for the past 40 k miles.

The second time (not related to the case above), I had the car on stands and with my son "driving" it in the air with 4x4 on, I heard a grinding noise coming from the front diff using a mechanics stethoscope. I was convinced I need a new front pumpkin. I removed the front driveshaft and the noise was gone. After a close inspection, I found that one of the 4 caps had the needle bearings completely seized and the cap was "welded" to the cross. $ 20 later the truck was quiet like new. I figure the bad u-joint was transmitting the load and vibration to the diff.

My point of removing the driveshaft was to see if the noise is gone, and to inspect both ends of it while out with your eyes and hands at no cost :)
To see if the front bearing on the TC is good, see if you can "shake it" around, otherwise, not so easy to diagnose.

Over the years I learnt that when if the noise is continuous, it's related to the drive shafts, tranny or TC.

If you can hear a whooh-whooh-whooh driving around 30 mph, then it's a bearing / CV shaft /or bad tire since those have about 3 times lower frequency than the drive train itself and you can hear it more clearly and differently.
 




USMCBuckWild

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In for results. I have similiar noise and have not been aboe to isolate yet.
 




tripplec

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It may be a bearing going in the diff. Have you every changed the gear oil in it or checked it? A cheap fix if it helps typically a liter of GL5 but I am looking at one of these and not up to speed on the fluid but the manual will specify if its GL5 75W90 synthetic or such.
 








USMCBuckWild

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So I replaced both of the front wheel bearings with brand new OEM units and removed the front driveshaft..... still have the slight grinding noise when turning to the right.

Starting to think its the front diff. I replaced the diff fluids last year with AMSOIL, made a huge difference in rear diff.
 




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