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Transmission & Drive train

AWD/4WD thumping under acceleration

This is a discussion on AWD/4WD thumping under acceleration within the Transmission & Drive train forums, part of the Ford Expedition Forum category!
Hi, I have a 99 Eddie B. AWD that when you are accerating makes a thump/clicking sound in the front ...

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Old 10-09-2010, 12:13 PM   #1 (permalink)
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Default AWD/4WD thumping under acceleration

Hi, I have a 99 Eddie B. AWD that when you are accerating makes a thump/clicking sound in the front end. I believe that it has something to do with, (this when the problem started) I had to replace a tire, even though it the same size it must be a tad taller than the old one. Causing the AWD to send power up front....But it sounds like something is wrong?????? I'm going to replace the other 3 tires to match put just curious if anyone eles has had this problem.

P.S. It also doe it when I put the selecter swicth in 4hi and 4lo.

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Old 10-10-2010, 12:37 PM   #2 (permalink)
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I've heard sometimes if your tires are off by a bit iw will cause the awd tokick in. Try unplugging the fuse under the hood for the 4wd and see if the noie is still there.
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Old 12-07-2010, 10:22 AM   #3 (permalink)
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Default 99 Expedition

Mine is doing the exact same thing. I pulled the fuse and it stopped. what does that indicate? Will it hurt to drive it without the fuse?
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Old 12-07-2010, 11:16 AM   #4 (permalink)
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pulled what fuse?? AWD fuse or 4x4 in general? Mine does something similar, my tires jump and scuff on the pavement when im in 4L and Im turning, it will also stop it self like im riding the brakes when Im in 4L. 4H and AWD, it doesnt do that. But there is a significant amount of growling sound especially when turning while the 4wd is engaged. What would cause that? Is there a write up on How-To change the rear end gear oil and transfer case oil? Im pretty sure its NEVER been changed and will probably need to be done soon. Its getting cold here!
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Old 12-07-2010, 05:18 PM   #5 (permalink)
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there is a write up on how to change rear diff fluid. and it is pretty much the same thing for the front, just different viscosity fluids. for transfercase, it is like changing your transmission fluid. there should be a port to empty it and another to fill it. if you are in 4L and turning on pavement, you are going to get a lot of resistance, almost unnatural feeling. if you are getting "growling" while turning in 4H and A4WD, then you may need to change out your CV shaft.

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Old 12-07-2010, 10:52 PM   #6 (permalink)
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Its because of changing the tire, any diameter change on the tires over a quarter of an inch in difference will throw the speed sensors off, and will think its slipping and cause it to lock in and out of 4h, and it is fuse number 104 under the hood and will not hurt it one bit check out the brown wire mod works good and lots of fun in two wheel drive with all that power ........Light em up easyyyyyyyyyyyyyyyyyyyyy
1999 EB expy
5.4L a4wd
149000 miles
2000 on new engine

Last edited by xcaliber1972; 12-07-2010 at 10:56 PM.
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Old 12-07-2010, 11:52 PM   #7 (permalink)
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i dont really have much faith in this "brown wire mod". they guys that have done it say their front tires still spin on the lift...i would love to ditch the A4WD!

01 EB. 4" Rancho Lift. 35" Nitto AT on 18x9 KMC. Warn hidden winch mount with XRC8000 winch.
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Old 06-11-2014, 07:18 PM   #8 (permalink)
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Default A4WD is not AWD

First of all, the Expedition does not have All Wheel Drive. It has 4 modes: Rear Wheel Drive, A4WD (Not AWD) which is Automatic 4 Wheel Drive, 4 Wheel Drive Hi range & 4 Wheel Drive Low range.
A4WD works like a limited slip differential, when the sensors detect rear wheel spin it engages the front differential making it 4 wheel drive.
Secondly, 4 wheel drive should not be engaged on pavement, wet or dry. It should only be used on loose gravel, heavy snow, mud and other such surfaces. On pavement there is not enough slip between the tires & surface which causes the drive components to bind up, when they do, something has to give, if it's the tires scraping or hopping you're lucky but if not the drive shafts, yokes, U-Joints, transfer case are all under stress, when it pops, you'll know it.
On dry/wet pavement & puddles you should use 2 Wheel drive, on light snow (or wet, if you like) you should use the A4WD.
If you want to see about that binding I mentioned, go into a parking lot, engage 4WD, turn the wheels fully left or right, put into drive (or reverse), and take your foot off the brake slowly. Let it roll slowly, it will come to a stop by itself very shortly. This is what your car is trying to do when you're incorrectly using 4WD on the roadway. The reason is because the wheels & axles are turning at slightly different speeds, which causes the binding of the drive-line.
AWD that some vehicles like Mercedes, Subaru etc have uses a transfer case that allows slippage between the front & rear differentials actual 4WD does not. So called Full Time 4 wheel drive is basically AWD.
Some of the older Expy's don't have the 2WD position, so for most driving, you'll use the A4WD mode which will run as rear wheel drive till needed.
All tires should be the same size (un less you pull the 4WD fuse or you have 2WD mode), if not the sensors see the difference in speed as wheel slip.

Last edited by Freightshaker; 06-11-2014 at 07:27 PM.
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Old 07-03-2014, 05:56 PM   #9 (permalink)
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Default is there a way to trick the auto 4wd?

sorry if this has been fixed before but i'm knew to the forum and pulling fuse 104 fixed my issue of the 4 wheel drive kicking in and out while driving and turning. my question is, that since it looks at wheel speeds to tell which one is slipping and if it should use 4 wheel drive or not, is there a way to splice in the front speed signal wire to the rear tires. so the truck only sees the rear tire speeds .. meaning that the front left (signal wire) is spliced in with the driver rear tire speed sensor. and the same thing with the front passenger signal wire spliced into the passenger rear tire. that way the front and rear will show the same speeds and thus not showing slip and not turning on the 4 wheel drive.. if that works then we can keep the fuse 104 plugged in and if we want 4 wheel drive we switch it to 4hi and 4low.. if we want 2 wheel drive we just put it to A4WD and since the wires are spliced it shouldnt see it slip and stay in 2 wheel even if you do burn outs. if someone has tired this i'm sorry for suggesting it. i just would like to have 4 wheel drive control instead of taking the fuse out. i just got the 2000 xlt 4.6l today and already have to pull a fuse for it to drive ok.

(edit) ah nevermind. there seems to be an easier way by putting a switch on the brown wire to disable the A4WD yet still keep the 4hi and 4Lo ..

Last edited by expeditiondaily; 07-04-2014 at 06:09 AM. Reason: searched more
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