Acceleration Whine & Coasting Rumble

[mranderson214]

Hi Everyone,

Facts:
I have a 2002 Explorer XLT, 183,350 miles on it, V6 4.0 L, stock, 4x4 etc. Lately I've been having some strange things happening when I let my foot off the gas or accelerate from a low speed constantly.

Symptoms:
Basically when I accelerate constantly (like turning a corner at a low speed and picking up speed to about 45mph on a straightaway), I'd hear a whining sound that sounds similar to the sound that your tires make when going over a patch of concrete bridge or something on an interstate. This sound generally happens between 30 and 40 mph. The sound isn't too loud and in fact, I think most people don't even notice it. The sound seems to change with speed, it gets slightly more high-pitched as I go faster and faster.

Also, the most ridiculous symptom comes when I'm going at about 40 or 50mph (or faster) and let my foot off the gas to decelerate, like coasting to a stop. What happens is that I feel a constant "thoom thoom thoom". The thoom that I'm referring to is similar to the pulsing that you get if say something was stuck on your car tires. Imagine if a piece of wet road tar has gotten on your tires and then your tire just keeps picking up random debris as it drives along. That's the kind of vibration that I get. The best way to describe it is that it feels like something is stuck on the tire but only when I decelerate.

This happens both when I apply the brakes above 40mph or if I just let it coast to a stop from above 40mph. This symptom is most noticeable when I am driving down the interstate and I let off the gas at 70mph and let it coast down to say 55 mph. Or use cruise control to keep my speed at 70mph, it can happen too but its worse and most prominent when I let it coast or begin braking from high speeds.

I really feel the rumble in the seats and the floor, so I'm slightly more inclined to think that there is a problem in the rear end. [correct me if im wrong]

What I've Tried/Changed:
I was told by a repair shop that my rear struts, rear toe links and front driver wheel bearing was bad.

I recently had my tires balanced about two weeks ago. I just had the rear toe links changed this past Saturday. My rear brake rotors are about 6 months old, rear brake pads were done about a month ago. Front brakes are good. The front upper control arms were just changed about a month ago. I also got a wheel alignment this past Saturday as part of the toe-link install. With all of this, I still have the problem of the rumbling. I also got new tires installed about a month ago. There's no unusual wear patterns on the rear tires (or front tires either).

Ideas:
What do you guys think it might be?

Is it possible that the rear struts can cause this? The problem with my rear struts is that the coil springs are beginning to crumble along the edges. I plan to get them changed in the near future but there's still enough coil there to hold it up, just the tips of the springs are beginning to fold into each other.

Might it be a rear wheel bearing?

I've read up on some rear differential problems with the 02's and 3rd gen's in general but I don't have any fluid leakage; nor do I hear sounds similar to what I heard in some videos about bad rear differentials.

Thanks in advance!

 

[jeff4912]

Sounds like wheel bearing possibly.

 

[mranderson214]

[MENTION=52746]jeff4912[/MENTION] thanks for the reply.

When the weather lightens up a bit, I plan to jack it up and check the wheels to see if there's any play in them. I know that the drivers front wheel bearing is going but it feels like something in the rear to me because i feel the thumping in the seat/floor and not so much in the steering. would a front wheel bearing give it more of a shake in the floor and not the steering wheel?

 

[pet575]

Agree that wheel bearing is a possibility. Another possibility is that if your rear struts are that worn your rear tires could be cupped if they have not been rotated regularly. Cupped tires will cause shaking and will make the sound you are describing.

I'd rotate the tires and see if things change. Like, if the shaking moves to the front floorboards, dash, steering wheel, etc. along with the location of the noise. If they do, you have some answers.

 

[mranderson214]

[MENTION=84796]pet575[/MENTION]: Thanks much for your reply. I think it might be the struts. Now that I put two and two together, with what you mentioned, I think it makes sense. I remember when the mechanic in the shop showed me the struts, he mentioned that one was leaking a little, not bad, but still leaking. When I accelerate the whining sound seems to be coming mainly from the back passenger side of the vehicle. Thats the same strut that he showed me was leaking a little.

So I guess your theory about the struts causing the sound is more than feasible. The tires are in good condition but I guess that might just mean that they havent started cupping yet. I'll look into getting the struts replaced. I just was confused if it might've been the struts directly causing this problem or if it was something else.

Thanks for the help!

 

[pet575]

My comments about struts were not intended to address the whining sound. I think you'll still have the whine even if the struts eliminate the thumping sound.

Be prepared for neither sound to go away just by replacing the struts. If they tires are actually cupped, the only way to fix that is to replace the tires. Again, entire possible that you could replace struts and tires and still have both noises.

For the whining (and possibly both noises), you have to consider the wheel bearing(s) and the differential in these vehicles. They are known weak points.

 

[mranderson214]

[MENTION=84796]pet575[/MENTION]: thanks, I'll keep that in mind. I haven't gotten the struts replaced as of yet so I wont rule out the differential problem. The thing is that the only wheel bearing on the vehicle that I've been told (by multiple shops) is going out is the front driver side. Yet, I don't know if the front driver side bearing would give me the rumble and whining sounds that sound and feel like they're coming from the rear end.

As for the differential, I haven't had any other symptoms that I read up on that correspond to the infamous rear differential problems on this particular model year explorer. I won't rule it out though. Thanks for your input.

 

[mranderson214]

So Today I realized something that may be of some use to getting the problem solved. I'm not sure if the whining and rumbling are related, I think they might be. I think I found the problem that was causing the whining, at least narrowed it down. The whining seems to be coming from the transfer case.

I was driving down the road at 45 mph and got the whining between 30 and 40 as usual. But this time, I pressed 4x4 High on the dash, as I was slowing down. I realize that I didnt get the rumbling when I was in 4x4 High but as soon as I put it back in 4x4 Auto, I had the rumbling as I was coming to a stop.

The whining sound that I've been getting seems to be similar (if not directly caused by) the whine of having the truck in 4x4 High while driving on regular pavement. I normally drive with it in 4x4 Auto unless its really bad, then I'll use High to get out of a parking spot or something. I usually never use High (or Low).

So in conclusion, it seems that if I have it in 4x4 High while accelerating, I dont get the whine, and if I have it in 4x4 Auto while accelerating, I do get it. When I have in 4x4 high as Im coming to a stop, I get a whine (normal when using High on dry pavement), but I dont get the rumbling. And when I'm coming to a stop in Auto, I get the rumbling.

What does this mean for the transfer case? Is this because I dont have 4 of the exact same tires on the front and back? I have 2 tires in the front at 235/70/16 and two tires in the back at 235/70/16. All are in good condition but the two in the front have a different thread pattern than those in the back. Or might this be because I need fluid or something? Any ideas?

Thanks for the help/advice.

 

[tursky4]

So Today I realized something that may be of some use to getting the problem solved. I'm not sure if the whining and rumbling are related, I think they might be. I think I found the problem that was causing the whining, at least narrowed it down. The whining seems to be coming from the transfer case.

I was driving down the road at 45 mph and got the whining between 30 and 40 as usual. But this time, I pressed 4x4 High on the dash, as I was slowing down. I realize that I didnt get the rumbling when I was in 4x4 High but as soon as I put it back in 4x4 Auto, I had the rumbling as I was coming to a stop.

The whining sound that I've been getting seems to be similar (if not directly caused by) the whine of having the truck in 4x4 High while driving on regular pavement. I normally drive with it in 4x4 Auto unless its really bad, then I'll use High to get out of a parking spot or something. I usually never use High (or Low).

So in conclusion, it seems that if I have it in 4x4 High while accelerating, I dont get the whine, and if I have it in 4x4 Auto while accelerating, I do get it. When I have in 4x4 high as Im coming to a stop, I get a whine (normal when using High on dry pavement), but I dont get the rumbling. And when I'm coming to a stop in Auto, I get the rumbling.

What does this mean for the transfer case? Is this because I dont have 4 of the exact same tires on the front and back? I have 2 tires in the front at 235/70/16 and two tires in the back at 235/70/16. All are in good condition but the two in the front have a different thread pattern than those in the back. Or might this be because I need fluid or something? Any ideas?

Thanks for the help/advice.

this could very well be your problem.. the auto 4x4 is ran off of the abs sensors even tho the tires are "the same size" they may not actually be the same due to tread height, circumference, and tread pattern. i was always told with any auto 4x4 vehicle as long as awd vehicle to have the same size, brand, and tread pattern all the way around or the auto 4x4 system could go crazy or even damage it. i know tires are very expensive but the drive train is a lot more expensive i would consider getting new tires all the way around

 

[delaware74b]

mranderson214 - your tires are mismatched in rolling diameter. I have an '04 that had the same problem on coasting around 45mph. It was very pronounced, except it didn't do it until the drivetrain warmed up (after 5-10 miles driven at 55 or more). It bucked and lurched on decel until it reached 35.

There was a tsb on this problem. If you were to measure each tire's circumference (tire rolling diameter), I bet you will find over 1/2" difference between the largest and smallest tires.

What is happening? The 4x4 (gem module) is reading the rolling mismatch as a slip condition (based off the abs wheel sensors at each wheel). The gem module locks the front axle to correct the 'slip condition'. It then unlocks the axle when the 'slip condition' no longer exists. When you force the 4x4 into 4-hi, you're taking the control of the front axle and that's why it doesn't have this issue in 4-hi.

Bottom line: 4 new tires of same brand and series will correct the thumping on decel. Rotate tires per manual's recommendation (pattern and mileage).

 

[mranderson214]

Thanks for the replies everyone.

My apologies on such a late response, its been a bit crazy with projects and midterms. So basically, the problem seems to have been the different tires after all.

I had been without 4x4 for a few years because my control module had went out (another TSB), I recently got a new one and put it in myself back in November and never paid attention that this whining noise started shortly after I got my 4x4 working again. I forgot what it was like having 4 wheel drive for a while

That being said, as things are still crazy with school, I unplugged the control module again, giving me only rear-wheel drive. That shouldnt be a problem because the snow should almost be over. I noticed that when I disconnected the control module, the sounds disappeared again. Next time I buy tires, I'll make sure to get them of all the same thread, size and manufacturer.

I got the updated control module so it shouldnt be an issue when I go to reconnect it, and even if an issue does arise; I'd rather have to pay $175 for a new module as opposed to leaving it connected and have to pay for a new transfer case.

Thanks for the help again!

 

[stefanjmsr]

So Today I realized something that may be of some use to getting the problem solved. I'm not sure if the whining and rumbling are related, I think they might be. I think I found the problem that was causing the whining, at least narrowed it down. The whining seems to be coming from the transfer case.

I was driving down the road at 45 mph and got the whining between 30 and 40 as usual. But this time, I pressed 4x4 High on the dash, as I was slowing down. I realize that I didnt get the rumbling when I was in 4x4 High but as soon as I put it back in 4x4 Auto, I had the rumbling as I was coming to a stop.

The whining sound that I've been getting seems to be similar (if not directly caused by) the whine of having the truck in 4x4 High while driving on regular pavement. I normally drive with it in 4x4 Auto unless its really bad, then I'll use High to get out of a parking spot or something. I usually never use High (or Low).

So in conclusion, it seems that if I have it in 4x4 High while accelerating, I dont get the whine, and if I have it in 4x4 Auto while accelerating, I do get it. When I have in 4x4 high as Im coming to a stop, I get a whine (normal when using High on dry pavement), but I dont get the rumbling. And when I'm coming to a stop in Auto, I get the rumbling.

What does this mean for the transfer case? Is this because I dont have 4 of the exact same tires on the front and back? I have 2 tires in the front at 235/70/16 and two tires in the back at 235/70/16. All are in good condition but the two in the front have a different thread pattern than those in the back. Or might this be because I need fluid or something? Any ideas?

Thanks for the help/advice.

with all 4 tires off the ground, truck in drive rear wheeles dont move smoothly