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2003 Mercury Marauder

As I’m sure you’re aware, the Marauder came with different tires sizes. 235/50/18 Front and 245/55/18 Rear. I missed the opportunity to purchase the OEM BFG KDWS this year, so I had to replace with Goodyear 245/45/18 Front and 255/55/18 Rear. Now I have a growling noise coming from the rear of the car. Could these tires have caused my rear end gears to go out in an 80 mile trip?

If both tires on the rear are the same size, the differential does not care what speed the the rear axle rotates, and would not cause a grwl. The small diffeerence in size also would not cause any scraping on the fenders. You need to go back to the tire store and ask what they did to your car. At least have the rear end fluid checked. Does this car have a limited slip differential? My Caprice did the same thing and I had to add a limited slip compound to stop the growl.

In any case, don’t keep driving it; go to a good driveline shop,don’t wait since rear end repairs are very expensive.

Good news. I just replaced the gear oil and the “growl” seems to have subsided. It was kind of thin. Now I still have the slight thump at low speeds that increases to a low “rumble” at high speeds. Tire dealer says that nothing is wrong with the tire. I tell ya, these goodyears are wearing me out. Any ideas on that noise?

I had one of these rear ends fail on a '92 Crown Vic after 200 miles running the “space-saver” spare tire…That issue does not apply to your situation however. Should the rear end turn out to be problematic, any axle assembly out of a '98 or newer panther platform car will replace it. Just be careful to maintain the same axle gear ratio.

Sounds like the posi-tracion (Trac-Loc) might be failing. When you replaced gear oil did you use also use the additive that keeps the Trac-Loc happy? Some gear lubes, mostly synthetics already have it blended in, but most dino lubes do not. Either was the stock posi-unit is pretty marginal at best, but it’s cheap and easy to rebuild should you need to.

Could a poor alignment cause this thumping noise? I had the car aligned when I put the new tires on. This thumping at low speed and rumble at high speed did not start until I had the new tires and alignment done.

Very good point.

Good news. All is not lost. Ends up the bearings had failed. Bad news is I needed new axels and bearings. Evidently the BFG tires masked the sound of the bearing growling before. New bearings, new axels and I am riding on glass.

Just FYI, the differential definitely requires friction modifier added if it is Trac-loc. I believe that all modern Marauders are Trac-loc, but I am not sure. There was a short period, a year or two, in the early 21st century when Panther Platform (Crown Vic, Grand Marquis, Town Car, Marauder) cars had poor rear wheel bearings. You car may fall into that category, but I don?t remember the years.