Having Difficulty Diagnosing Rumble - Not the Usual Suspects

[Tenpoundburrito]

Hello, everyone! This is my first time posting, but I've been browsing around for quite awhile trying to solve this issue. I'm experiencing what I believe to be a unique problem. I've seen a few other posts with this same issue dating back to the early 2000s, but none of the fixes that worked for them have worked for me, hence the reason I'm posting this now. I'm hoping someone will have some ideas for me to look into.

First off, my vehicle specs. I have a 1999 Mercury Mountaineer with the 302 V-8 and AWD. It's riding on the stock-sized P235/75/R15 tires (Goodyear Wrangler Radials). It does not have the Automatic Ride Control, and it's about 99% stock. It has 141,000 miles on it. The problem just started about 300 miles ago.

Next, the issue. The problem I'm experiencing is a rumble that feels exactly like a tire rubbing. It only happens when going around medium to sharp corners at lower speeds. Basically, with the steering wheel turned about 90 degrees or more and speeds under 15 miles per hour. It's also only noticeable inside the vehicle. Someone standing outside cannot hear it or see anything shaking or vibrating.

There's no pattern to it. It does it with the vehicle cold or warmed up, hot weather and cold, rain or dry, even and uneven ground, drive and reverse, pavement and dirt, and accelerating, braking, and coasting. Sometimes it goes away completely for a few turns and several miles, then comes back. Mostly it's a light shudder, but occasionally it will rattle the dashboard and tailgate.

It mostly feels like it's coming from the center passenger side of the vehicle, right under the front passenger's seat and floorboards. The only problem is, the only thing there is the exhaust.

Now, what has been tried.

1. We changed the rear differential fluid and replaced it with synthetic 75W140. This was when it started, about half an hour after changing the fluid. I then added a 7 ounce tube of Trans-X limited-slip differential friction modifier and drove it for three days (about 90 miles) with no change.
2. It doesn't do it when stationary, and we checked the power steering pump which is functioning properly.
3. We checked the CV joint, which is brand new, and it's functioning properly.
4. We checked all the universal joints, and they're all either new or functioning properly.
5. We checked the hubs and wheel bearings at all four corners. All four are functioning properly.
6. We changed the transmission and transfer case fluids and replaced them properly (Mercon V in the transmission and Mercon III in the transfer case) along with a Hastings transmission filter. No metal shavings in either. No change in the noise.
7. We checked the front ball joints. Both uppers were going bad, so I replaced them with Moog R-Spec upper control arms and ball joints. I also greased the passenger side properly (driver's side is non-greasable). No change.
8. We checked both driveshafts and both front CV shafts. All are functioning properly.
9. We replaced the rear leaf springs and shocks which were getting worn out, but no change in the noise.
10. We checked the exhaust system for movement, but everything is solid and in place.

So, long story short, it's not the differential, power-steering, hubs, ball joints, control arms, transmission, transfer case, driveshafts, CV joint, CV shafts, u-joints, wheel bearings, springs, shocks, or exhaust. Does anyone have any other items I might inspect or ideas as to what it could be? I would greatly appreciate any help I could get, and thank you.

 

[Tenpoundburrito]

I forgot to add this in the first thread, but we also checked the front differential, and it is functioning properly. In addition, we looked for the obvious, but none of the tires are even close to rubbing against anything.

 

[MAS Tequila]

There is a seal on the back of the backing plate that seals the axle from the wheel assembly.

I can't remember the name of it.

Have you tried lubricating those?

Lift the front end of the truck and look where the axle meets the backing plate.

Spray some wd-40 or silicone or whatever on it.

See if this helps.

MT

 

[Harpua216]

Hi! I have a 99 Merc AWD 5.0 and just did everything you mentioned as well. I am lucky enough to have a used tire shop around the corner that puts up with me. After all the work was done I rotated the tires but had the throw them on the balancer. low and behold, even with new tires, the worn ball joints and shocks had flattened them in places and crowned them in others. it wasnt visible while on the truck, but you could totally feel it and barely see it on the balancer.

not believing this AT ALL, i bought some used tires for the front and took it for a spin.

vibration gone. really the moral of the story is that the vibration WAS the control arms shocks, etc.. and it made the tires that way too.

just a thought.

 

[Tenpoundburrito]

Thank you both for the advice. I did check the seal on the backing plate, and it was fine, but it was a good suggestion. I also added another bottle of Trans-X to the rear differential.

As for the tires, that may be it. I know that at least one of the tires is out of balance because it also vibrates a little bit above 58 miles per hour, just like a tire out of balance or a bent rim (same thing was on my 1999 Ford Taurus - bent rim). I'll be balancing them in a week or two when I'm at my Grandma's shop.

I say if it hasn't gone away, because the problem is nearly gone now. I used the Mountaineer to pick up a 4,000 pound cherry-picker lift to do some work last weekend, and it didn't make the noise the whole way there or back that morning. It made the noise almost constantly when maneuvering the trailer in the yard that day, then went away when returning the lift the next morning.

Yesterday, I drove my brother back and forth about 15 miles each way, some of it off-road, and it only made the noise twice, both times very briefly.

The only other theory we have at this point is that since the Mountaineer had been sitting for awhile, and we spotted a few surface rust spots on the rear differential gears when changing the fluid, it's possible the clutch plates in the limited-slip rear may have gotten a little rust on them. As I drive it, the rust may be wearing off again or the Trans-X is making it easier on the plates.

I'll keep this post updated when the noise has either completely gone or something breaks.

 

[jester1023]

Every 2nd gen that I've had gets the tire grumble when the ball joints need replacing. The extra play causes excessive uneven wear. The only time they can talk is when the wheels are turned. Then it seems like every other tread lug is contacting pavement...like a mud tire.

 

[Tenpoundburrito]

Updates:

I had the tires rebalanced (three were out of balance) by a well-respected tire shop in town. Sadly, this did not solve the rumbling problem but did alleviate the shaking above 57 miles per hour. They also inspected all four tires for uneven wear, but all four came out fine.

- jester1023 - When I replaced the upper control arms with new Moog ones, they came with the ball joints. The ball joints on the old control arms had both gone bad. It was a good suggestion, though.

I may have had success in another area. When I changed the transfer case fluid, there was no metal shavings in the fluid. I assumed that meant the transfer case was okay. One of my uncles was visiting from Florida, and he works for a Ford dealership down there as a diagnostic technician (he is now the eighth mechanic to inspect it). I told him all we had looked into, and he took it for a drive. It took awhile, but he finally was able to track down what he believes is the problem. He turned the wheel all the way to one side and held one foot on the brake while giving it enough gas to still move in a circle. The rumbling increased and was constant, literally shaking the dashboard and rear hatch (normally, a tight turn had no effect; it was only during minor turns). He diagnoses it as the viscous coupler inside the transfer case. He said because it's a sealed unit, it will go bad without dropping any telltale signs into the transfer case fluid.

I'm looking into either replacing it myself with a $200 one from online or having a nearby shop do it. I will update yet again when I have more details or it is fixed.

 

[swshawaii]

You've already inspected and no mention of it only happening when turning right, but easy enough to recheck. GL

10. We checked the exhaust system for movement, but everything is solid and in place.

RUBBING NOISE FROM REAR DURING RIGHT HAND TURNS-5.0L

http://www.bbbind.com/free_tsb.html

 

[PieceKeeper]

To Tenpoundburrito -- any updates on this? You seem to describe my problem well. I'm trying to search the threads to see who else has dealt with this problem. My Explorer is a rear wheel drive, 5.0L. No transfer case. And, the shudder only happens at speeds under 5-10 mph while turning. If i drive straight then no shudder. Looking for ideals.

 

[Tenpoundburrito]

Okay, the problem is finally (well, mostly) resolved! PieceKeeper, your timing couldn't have been better for asking for an update.

I spent a total of eleven hours underneath the Mountaineer a weekend ago. We changed the viscous coupler, and the problem has disappeared. I drove it a few times this week to make sure it didn't come back.

I have a few warnings/tips to anybody doing this on a 1998-2001 Mountaineer.

1. The Haynes and Chiltons manuals (I had both for reference) both say there are only five bolts to remove to separate the transfer case from the transmission housing extension. There are actually six, all thirteen millimeter, and three of them are incredibly hard to get to: the top two and the one on the right when facing the transmission (they're in a hexagon pattern). The one on the right (east) is blocked by the exhaust system on my V-8 model. They recommend pulling the exhaust down. Mine was too rusty to do this, so we actually cut it off. The other two are in an area where, even with the exhaust off, there's no room to get a regular ratchet or wrench in there. We ended up cutting a cheap brand thirteen millimeter wrench in half and using that, along with a strap to get leverage on it to loosen the bolts.

2. If yours is not in perfect shape, expect the bolts on the transfer case to be siezed up. Also, they are a torxs plus head, not a standard torx head (I believe it was a torx plus 45). We stripped a couple before we figured it out and also broke three standard torx sockets while using an impact to remove them. The bottom four bolts were unremoveable and had to be drilled out and rethreaded. You might want to be prepared for that as well.

3. I highly recommend a full car lift and a second person, especially if you don't have a transmission jack (which we didn't - it was holding a Blazer transmission that was being rebuilt).

4. Instead of a gasket, I used RTV Ultra Blue, but the recommended is RTV Black. I used the blue to make it easier to split apart in case something else went wrong. It's not leaking, but if it does, I'll update.

5. As always, antisieze everything that's threaded (Permatex Silver Antisieze) in case you have to pull it apart again someday.

Now to the "mostly" part. While the transfer case is not leaking, we kept the original gasket that seals the transfer case to the transmission extension housing, and it is. It looked to be in very good shape, but it's leaking between the bottom two bolts. It didn't start leaking until I had driven the vehicle three times (I checked each time), and is a very slow leak. I'm looking at having it replaced by a transmission shop as I'm just getting too busy to be fixing these things myself.

 

[Turdle]

Added to above
Removal of the center console will allow you to get to the access panel under it to remove the top 2 transfer case to transmission bolts. Believe me, it is faster that way.

Thanks for updating this thread!

 

[PieceKeeper]

wow. Impressive amount of effort! Thanks for the update. Not sure I'm up to doing that level of work. My '99 Explorer is 2WD. No transfer case, but does the tranny still have a viscous coupler?

 

[Tenpoundburrito]

Thank you for the hint on getting at those bolts through the center console. I wish I had known of that the first time. If the shop decides to charge too much, I may go at it that way.

Also, to answer the second question, I don't believe the two-wheel drive Explorers have a viscous coupler. The only purpose of the coupler is to transfer power to the front driveshaft and front wheels when the rear slips. Possibly check to see if you have a lock-up torque converter. I had a Bronco with an A4OD transmission that was making a similar rumble when I accelerated, and it was the torque converter.