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2003 Explorer thumping upon accelleration.

I bought a 2003 EB Explorer 4X4 in July, with about 34,000 miles on it. On a road trip, I noticed a vibration beginning, only noticeable at

65-70 MPH. I took a look underneath and only noted a slight leak from one of the shaft seals (between the rear differential and the left wheel). I took it to a service station, where they said the leak was minor and the differential had plenty of oil. They balanced the wheels, but the problem didn't really improve. They insisted that the vehicle would be OK until I got home from vacation.

So, once back to Ohio, I took the truck to the dealer (still under

36,000 miles, luckily). They replaced the gears in the rear differential as well as the seal (I now find that the diffential is a common problem with the 2002-2005 models). The problem was somewhat better, but not entirely. The problem was still manifesting itself as a thump while coasting at highway speed.

So, I took the truck for a second visit to the dealer, where they insisted that I needed four new tires (not covered by warranty - imagine that!). I told the dealer that was BS, and they instead rotated the tires and did a 4-wheel alignment. The problem wasn't solved, but the symptoms changed to a thump during low-speed accelleration. This change led me to believe there may be some validity to the tires claim, but two were nearly new, so I got the other two changed at the local tire shop. With the new tires and four freshly balanced wheels, the problem was worse than ever, so I asked the tire shop what they thought. They drove it, and said "No way is that caused by tires - It's definitely a drivetrain issue".

The posts here have several entries about differential whines, but has anyone experienced this thumping on accelleration? It almost feels like hitting a pothole or seam in the pvement. Though it is repetitive, it doesn't have a set rythm. For example, the thumps aren't closer together as speed increases, and there are sometimes longer pauses between them than others. My best guess at this point is that the differential is binding up, or a U-joint / cv joint (whatever they are calling them on the rear halfshafts) is bad.

Any ideas? I hope i can get my money's worth out of this, my seventh (and probably LAST) Ford.

Reply to
lastford
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Thumps in explorers that do not vary with the rotational speed of the drivetrain are often the full time 4 wheel drive misbehavin'

So if you have the full time four wheel, it may be over engaging the front axle. This causes windup in the drivetrain which will be released as a thump when something gives. Often the clutches in the transfer case slip with a thump. In auto four wheel, your font driveshaft can engage anywhere from about 10% I think up to 100%

Your thumps will go away on a dirt road, as the front tires can slip on the dirt. Perhaps the new tires are grabbing dry pavement better than the old ones, and that is what made your thump worse - your old tires were slipping off some of the tension.

Hope you are still under warranty.

Reply to
ross via CarKB.com

Makes sense - The problem was least with the old, worn tires on the front, worse with the good tires on the front and bad on the back, and worst with 4 good tires.

I never bought the extended warranty before, but something told me It might be worth it with all the gadgets on the Eddie Bauer - Lucky me.

Reply to
lastford

The dealer continued to isist that it was tires. They said that the newer models with 4WD are very sensitive to tire wear, and even slightly different tire diameters on the front and rear can cause binding in the transfer case. They tell me that even when the front wheels are not being powered, that there is still some connection to the rear wheels.

Anyway, they said all they did was change the tires, and it is fine now...very well behaved except for some tire noise around 65-70 MPH. It's not the differential whining...I think it's just because of the all terrain tires (BFG rugged trails).

Who knows - they said it took two days to get the tires in. Maybe they quietly rebuilt the transfer case and turned it in to Ford for warranty while soaking me for a pair of tires.

Thanks, Phil

Reply to
lastford

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