Originally Posted By: busfreak
Hi guys,
- above 80 kmph at the point of loading (acceleration) and unloading (deceleration w/o using break) there is a slight singing / whining from the rear
- the same singing is present in idler neutral gear between 80 and 100 kmph (just as additional info)
I dont know if it comes from diff or it is tramsmmitted from gearbox via power train - rear axle to car body.
What is possibly the best / most successfull diff lube to try to get rid of the slight noise ?
Who has experience ?
In car manual is recommended:
temp < -30 °C SAE 80
-30 < temp < 30°C SAE 90
temp > 30 °C SAE 140 °C
temps here are between -20°C in winter and 35°C in summer.
thanks for answer
Busfreak:
Vans/Buses are the most sensitive of any vehicle to amplifying ring and pinion whine through the body structure. American vans even specify certain ring & pinion sets to minimize vehicle owner complaints.
At very light load at highway speed, and to a lesser extent during a light coast, is when normal gear whine is most evident. If your gear whine is not increasing in volume or the range of speeds it is audible, and there is no excessive metal on the magnet in the differential housing, it is likely you have normal gear whine.
Although I have heard antedotal reports that gear oil can increase or decrease ring and pinion sound, I have never found any difference when experimenting by changing gear oils. Since the ring and pinion whine is caused by the particular ring to pinion gear contact pattern in play causing a vibration and resonance in the vehicle body, I cant see how an oil can affect this but so much. Maybe a thicker oil would give a thicker film when lightly loaded , but it is still two pieces of iron separated by a non compressible oil film. I would guess that when all the bearings are very lightly loaded as well as the gear teeth, the slack in the all the bearings as well as the gears allows these resonations to become more audible when they are at the resonant frequency of your vehicle.