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rhythmic thump....possibly transfer case or casr motor

explrr

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north kingstown, rhode island
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2003 ford explorer nbx,
Hello, I was wondering if anyone else has experienced this before and what the remedy is.

I have a 2003 explorer nbx v8. It has the selectable 4x4 with 4x4 auto, high and low. When I drive at speeds above 35-45 mph and let off the gas, while decelerating, the truck makes a rhythmic thump that sounds like you are going over the cracks in the concrete on the highway. It only does it during deceleration. I tried a little experiment to isolate the problem. iI wait until the truck starts thumping and I put the truck in neutral....the thump still occures. I then shut the engine off , while coasting on the highway in neutral and the thumping goes away. I start the truck and put it in drive and it comes back. I then put it into 4x4 high while driving and the thumping goes away. Wtf is it? haha . The entire transfer case? One piece of it? Just the selector motor is off a bit? Any onsite would be helpful. Thank you to all who respond.
 



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n2epv

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My 04 was doing that, it was the 4X4 clutch kicking in. The transfer case uses an electric clutch to engage the front driveshaft and a shift motor to change between high and low range. Pull the 4X4 fuse (#25 on my year) and see if the problem goes away.

I did the 'brown wire mod' and that took care of the problem.
 






explrr

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Awesome man thanks for the reply. I will definitely try that ASAP. Now I'm assuming I will lose my 4x4 when I do the brown wire mod so I'm sure I can put a switch in to complete the circuit whenever I need it back on
 






rrgone

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You could try rotating your tires to see if it makes any difference. Sometimes the control module is just too sensitive to slight tire size differences and thinks it is detecting wheel slip. I don't know why it happens only when you decelerate but I have seen it before. Sometimes a new 4X4 module will fix the problem but you definately want to do something to make it stop before it damages your transfer case. The brown wire mod is another option. Sometimes 4 new matching tires fixes it too. Let us know what you end up doing about it.
 






explrr

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You could try rotating your tires to see if it makes any difference. Sometimes the control module is just too sensitive to slight tire size differences and thinks it is detecting wheel slip. I don't know why it happens only when you decelerate but I have seen it before. Sometimes a new 4X4 module will fix the problem but you definately want to do something to make it stop before it damages your transfer case. The brown wire mod is another option. Sometimes 4 new matching tires fixes it too. Let us know what you end up doing about it.

That's funny you should mention that because there is one newer tire on the truck. Even though its the same size the tread difference could make it do that I guess. What I will do for now is pull the fuse and see if it works then get 4 new tires and then put the fuse back in and see if everything is all good
 






rrgone

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That's funny you should mention that because there is one newer tire on the truck. Even though its the same size the tread difference could make it do that I guess. What I will do for now is pull the fuse and see if it works then get 4 new tires and then put the fuse back in and see if everything is all good

If you have one odd tire that is most likely the problem. You could try rotating it front to back or vice versa and see if it helps, but ultimately you will need to get 4 matched tires.
 






explrr

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Just wanted you guys to know that I pulled the number 25 fuse in the engine bay box and it fixed the problem for now until I get new tires. Thank you again for the help
 






Shafner79

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Did the sound go away once you got new tires?
 






Jamie Jackson

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Mismatched Tires and 4x4 Auto-Switching

Thanks, explrr and n2epv!

I've been trying to get to the bottom of this issue for months, and finally happened to google "rhythmic thumping" plus the usual search terms.

My symptoms, with my 2003 Explorer XLS V6.

When getting up to 65 or 70 MPH, then letting off the gas and coasting, the truck would pull to the right (felt like driving through a puddle only on the right side), and would generally stay like that. Once I got down below, say 40 MPH, I would get that rhythmic thumping (a little faster than once per second, and it never varied--it was never faster or never slower, not even down at 5 MPH). If I applied brakes during the thumping, it was exacerbated.

The problem never happened if I coasted in neutral. Also, the problem often went away when I stepped on the gas again.

I thought it might be worn suspension components. I inspected the front end, and I did notice that I had bad upper ball joints and outer tie rod ends. I replaced the upper control arms, outer tie rod ends, and for good measure, the inner tie rods and lower ball joints. I also replaced the right front hub bearing. (It had no play yet, but it was getting slightly rough, and I already had a new one on hand.)

However, the problem persisted...

People told me that my rotors were warped, or my tires were faulty. I knew they weren't because the thumping would have changed frequency with speed, so I didn't bother pursuing those.

I notice that a the right rear coil spring was cracked, but since the rest of the rear suspension components looked good, I couldn't make sense of how the coil spring would contribute to a flat-ground, straight-ahead problem, I didn't bother with it. (I'll save that for another day.)

Others said it was binding calipers, which I thought sounded reasonable, but I couldn't make sense of why it would be intermittent. I inspected the right-side calipers, and did a full brake fluid change while I was at it. While I was in there, I cleaned out the right parking brake drum and backed off the tension on those shoes a tad, just in case they were playing a part.

Still, the problem persisted...

Others folks told me it was my CV joints, but they looked fine and I had no symptoms when turning in circles at minimum radius.

The interwebs (referencing different vehicles) told me it might be bad engine mounts. I inspected mine, and yes, they were bad, but I couldn't fathom how they could make the truck pull to the right. I'll also save *that* job for another day.

I do have a set of unmatched tires on the truck right now (because I'm broke). Some folks pointed to those as the source of the problem, but didn't elaborate on why that might be the cause, so I didn't really have a plan of action on that one.

Finally I found this thread today, and it was explained that unmatched tires can cause 4x4-Auto to switch on and off (because it *thinks* it detects slipping conditions). Finally, something that made sense! I didn't completely understand why that would cause a pull to one side while in 4x4-high, but I figured that all bets are off if you're driving at highway speeds on dry pavement with 4x4 engaged.

Today, I took the truck out and pulled fuses #17 and 18 (those are v1 and v2 4x4 fuses--maybe 4x4 low vs. high, I don't know). I tried to reproduce the problem with those fuses removed, and couldn't! Then I repeated the tests, both in and out, and all signs point to automatic 4x4 switching, and that's probably due to the unmatched tires.

So, I'm really happy to have found this thread. Now that I know I don't have any problems that would give intermittent alignment problems, I can finally get this sucker aligned!

Now, on to some questions of my own:

We're done with winter, here in VA, and I'm not going to need 4x4 (except in known, specific cases). Is there a difference between the "brown wire mod" switched "off" and having these fuses removed? What I'd like to do is keep the fuses out, get a new set of tires in the fall, and *then* put the fuses back in (like explrr's last post).

Does that sound like a plan, or will this have other repercussions?

Thanks,
Jamie
 






IPcamper

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I had a similar problem when I had miss matched tires on my explorer. I put new tires on it last fall and it would still seem to bind up the 4x4 once in a while. Often in a parking garage on tight turns, but also at highways speed when coasting. I read elsewhere, don't remember where, that suggested that a little sludge bills up on the clutch plates over a long time. Don't know if it does or not, but I followed the advice and I changed the transfer case fluid, ran it hard switching between in and out of 4x4 mode for a few days and changed the fluid again. The binding has gone away.
 






va2explorer

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I just posted to another thread on this issue before finding this thread, and I'm almost convinced it may just be the tires. I just recently went on a 1600 mile trip, and before going I installed (2) new used Bridgestone 255/55R18 tires with about 50% tread remaining on the rear of my 03 EX XLT 4.0 4x4, and the (2) front tires are Michelin 255/55R18 with about 50% tread remaining. The only thing that has me wondering if all the cases that had a tire size difference(issue) didn't also do some internal damage to the clutches in the transfer case, and the reason I'm saying this is because during the first 500 miles or so of my recent trip I did not feel the surging or the rhythmic thump as some call it. So that being said something was taking up the slack of the tire height difference, and after the "something" couldn't take up the slack anymore is when the surging/Rhythmic thump began. Now that it's 2015 I'm curious if some or any of the 2011/2012/2013 related threads. did anyone ever have any other failures after they either got 4 new tires or did the brown wire trick or unplugged the fuse.
 






Jamie Jackson

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Still Going with Mismatched Tires

Well, I still haven't found the budget to get a new set of tires, and the mismatched ones still have good tread, so I've been running with the 4x4 fuses out since March 2015. I popped them back in for a couple days when we got a ton of snow in the DC area this winter, but I'll be running rear-wheel drive until these tires are worn out.
 






oldgranola

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I'll bump this because I just really benefited from this thread. I also had a terrible intermittent thumping and whine, mostly on deceleration but it would continue until I could stop. 2002 ford explorer xlt 4x4 4L 138K miles with old tires. I thought for sure I was up for big $$ rebuilding the rear differantial, perhaps transfer case, front diff? Putting it into 4x4 high also caused a whine. Based on this thread I removed the #18 fuse in front for the PCM (v-batt-1) only which is enough to disable 4x4 auto. That made it impossible to make the issue happen (though I still do have some bearing noise etc to attend to). I took the money I would have spent and got all new tires and replaced the fuse. Bingo, that issue fixed. 4x4 high and 4x4 low also are fine now. Crazy. So definitly cannot use old or used tires on these things, needs a complete all-same set just like it says in the manual...
 






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