Does Your Car Need Rear Differential Repair? Here's How It Works

Rather than spending a huge amount on repairs, see how much your broken car is worth as-is. Or read on to compare your options.

Rear differential noise or leaks are costly

You have a heavy-duty truck or SUV for a reason – it works hard and has to be reliable. You keep close tabs on the engine and transmission, changing the fluid regularly to make sure they don’t break down. But have you paid any attention to your rear differential? If you haven’t given it any thought, it’s probably due for a rear differential service. 

If you have rear differential noise, which sounds like a whirring noise from the back of your car, it’s probably too late and a rear differential repair is in your future.  Starting to hear that clicking sound, or noise when turning may mean you'll have to figure out what to do with your damaged car, whether that's selling it or repair.

What Does a Rear Differential Do?

A driveshaft connects the rear differential mechanism to the transmission or transfer case, transferring the engine’s power to the rear wheels. The rear differential’s role is simple: change the power’s direction from longitudinal (along the car) and direct it to the wheels.

Gears inside the differential accomplish this purpose, providing a 90-degree direction change along the rear axles. The power is transmitted from the rear differential along axle shafts that connect to the wheels and rotate to propel the vehicle forward.

Rear Differential Service

The gears inside the rear differential are bathed in gear oil, which lubricates the gears and bearings and cools them to prevent overheating. The fluid breaks down over time, and metal filings from the gears and bearings collect in the fluid. Every once in a while rear differential fluid replacement must be performed. The gear oil must be changed to prevent damage to the gears inside, known as the ring gear and the pinion gear.

A rear differential service consists of removing the rear differential cover, cleaning any old fluid from inside the differential case, resealing the cover, and adding clean fluid. After a rear differential fluid change, most vehicles will go 20,000 to 40,000 miles before it’s due again.

Symptoms of Rear Differential Issues

Typically, there are two symptoms you’ll notice when you have a bad differential, or car differential problems:

• Rear Differential Noise – if you hear howling from the rear of your truck or SUV when you’re driving, it’s possible it’s rear differential noise. It can change in pitch as well as come and go depending on the severity of the issue and load on the diff. Many times, rear differential noise is mistakenly thought to be tire noise and ignored, leading to more expensive repairs.
• Rear Differential Leak – more commonly, the problems stem from low rear differential oil. Rear differential leaks are the culprit, either at the axle seals, the pinion seal (where the driveshaft attaches), or the rear differential cover. Light brown or grayish fluid on the ground under the back of your truck is an indication that you have a differential fluid leak. Rear differential leak repair costs can range depending on whether they are light repairs such as replacing the oil seal, or adjusting backlash, or if you need to overhaul and rebuild the differential.

Types of Rear Differential Repairs

Obviously, the less intrusive the repair is a rear differential oil leak before it causes other issues. Different oil leak repairs include:

• Rear differential gasket replacement. The rear differential cover is typically silicone or rubber and can deteriorate and leak. It’s the easiest to repair – all that’s required is removing the rear differential cover, cleaning the sealing surface, and resealing the cover. It’s all done in less than an hour.
• Rear differential pinion seal. At the front of the differential is a yoke that attaches to the driveshaft. The seal around the yoke can develop a leak over time, either from nicks in the rubber or from age. This can take a bit more time to repair as the yoke needs to be removed, the seal pried out, and a new seal driven into place without damaging it.
• Differential side seals. These seals prevent the diff fluid from leaking onto your rear brakes. It’s more intrusive because the axle shafts must be removed. The old, leaking seals are pried out and new ones are carefully installed before the whole assembly is put together.

Other rear differential repairs might be:

• Rear differential bearing replacement. There are side bearings and a pinion bearing which can pit or deteriorate, causing your rear differential noise. These bearings are part of a rear differential overhaul, taking three to five hours to complete.
• Replacing the rear differential gears. When teeth on the gears have chipped or worn badly, they must be replaced to eliminate the noise and potential for failure. These ‘hard parts’ are the costliest components, and repairs can only get one step worse.
• Complete rear differential replacement. If the gears have ‘grenaded’, the case might not be salvageable. That’s when a complete rear differential replacement comes in – housing, gears, bearings, seals, and all.

Rear Differential Repair Costs

Most seals and bearings are relatively inexpensive on their own. Combined with the few hours of labor required for their replacement, the typical rear differential cost of repair is between $200 and $400.

If gears are required, that number jumps a bunch. Rear differential repairs that include a new gear set may be $1,500 or even higher between parts and the labor to replace them. These are among the more expensive auto parts out there. As you can see, a broken differential can be costly.

Rear Differential Replacement Cost

If rear differential replacement is your only option, you can seek out a completed used assembly. A good used part with a decent warranty will be around $1,500 to $2,000 installed. Rear differential replacement with a brand new component is higher, around $3,000 to $4,000 in all.

What About Selling My Car to CarBrain?

If you don’t care to deal with rear differential repairs or they are outside your budget, you could sell your truck or SUV. Unlike the frustrating sales process selling your damaged vehicle privately, CarBrain is easy to use and fast! Simply request a quote for your vehicle in ‘as-is’ condition. Based on your vehicle’s information and condition, we offer you a fair price. Once you accept the offer, we’ll pay you for your vehicle and have it picked up. There’s no charge to use our service, and you’ll get money for your broken-down vehicle.

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