How much work the mechanic has to do to repair the differential depends on what damage has been done already. In some cases, it is just a fluid change, which can take as little as 30 minutes. Other times, entire pieces of the differential will need to be replaced, which can take hours. The severity of the complications if the rear differential goes out while driving with a bad pinion bearing will depend on the problem and the vehicle. In the case of chipped or broken gear teeth, there may a vibration or skip in power. Multiple broken teeth will likely cause thunks and rattling sounds.
What are the signs of a bad rear differential?
- Noise in gear from an idle. When the vehicle is turned on and first put into drive, there may be a rattle or clanking noise coming from the rear of the vehicle. This noise may be attributed to the drive shaft universal joints. These joints connect the transmission to the rear differential; and if they have worn down, they could impact the differential by forcing it to work harder, thus wearing down its gears. In order to check the gears of the rear differential, a certified technician will need to be consulted as the procedure requires equipment not commonly available to the consumer.
- Grinding Gears at Speed. When the vehicle accelerates, there may be more noises like a hum or continued clank from the rear. This can be due to the gears in the rear differential being stripped or partially worn which creates an awkward motion as they spin the drive shaft. Noise may be especially bad when the driver accelerates the vehicle quickly and is forced to brake rapidly.
- Vibration and Fluid Leak. Worn or ripped universal joints will also cause vibration along the drive shaft and into the engine block via the transmission. This may be felt at high speeds in the body of the vehicle or through the floor. The rear differential and universal joints also have seals and use lubricant to work properly, and a leak or crack in a seal may contribute to vibration and failure of rear differential gears. Look for any fluid pooled at the rear of the vehicle after it has sat overnight.