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I have a 2000 Excursion, 2WD, 5.4 L, Automatic transmission with 91,000 miles. It has a 3.73 regular differential. Around 80,000 miles it developed a whirring sound when decelerating that seems to originate towards the rear of the vehicle. At the slightest touch of the accelerator pedal, the noise stops. I can place the transmission in neutral while decelerating and the noise is still present, but it is again quietened by depressing the accelerator pedal just slightly (transmission/torque converter issue??). The noise is louder when decelerating while towing a load. I serviced the transmission at 60,000 miles, it shifts and operates very well. Any thoughts or advise would be appreciated.
Sounds like the bearing in the front of the differential or could be gear whine. Either way, I think you'll need to get it serviced.
You can start with changing out the fluid and see if that helps. That way you'll at least know the fluid level is correct.
Welcome to FTE!
Again, Monsta beat me to it.
My diff developed the same sound once in '03 when Houston flooded and I hit some deep water and again in '05 when the fluid somehow became contaminated. Both times I changed the fluid and it solved the problem. If you do have it done or plan on doing it yourself, use the recommended oil, no additives. Lucas and a few others seem to cause more trouble than they're worth. You may get a great initial response, but you'll be sorry later.
Thank you for your responses. I did change the differential oil recently, the level was OK. I will admit that I used Lucas Oil based on a recommendation from someone. The noise seems to be a bit worse using Lucas. I have only driven 75 miles since the changeout. I will replace the oil again with a correct, high quality synthetic to see if my noise changes (hopefully quieter).
It's a standard differential so I didn't use any friction modifier. I just refilled the differential with Mobil 1 75W-140 Synthetic. The noise has not changed. I suspect a trip to the local clutch & gear shop is in order. Their estimated price to replace ring & pinion gear, all bearings and gaskets ....... $850 -$1250. Ouch.
i dont think you need a new set of gears. most likely you just need the backlash set to specsor the pinion depth is off too. if they are going to pull it apart, just have them replace the bearings, check pinion depth, and set the backlash to .001-.005" . that would take care of the noise. the gears themselves would not make the noise. its the backlash. when you take you foot off the pedal, the back dide of the gears touch. thats what the noise is. i would use some marking paint to check both sides of the gears before you pull it apart.