The transmission in my car is slipping and the differential is whining.
Sounds like you are having two issues. The differential making noise is usually due to the gears wearing irregularly. This can be caused by low fluid levels or worn bearings in the unit itself. A check of the wear pattern on the gears as well as the backlash will determine what repair will need to be done to correct it. If the transmission is an automatic, a bad sensor, or actual clutch pack wear inside the transmission could be the cause. In both cases disassembly is required to some degree for a proper diagnosis of your transmission. If it is a standard transmission, your clutch might be worn out. If this is the case, the clutch and all related components will need to be replaced. In any of the cases above, the work should be done by a qualified mechanic.
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