Compare Exhaust Back Box (Silencer) Replacement Deals

What Does an Exhaust Back Box Do?

The back box, also called the rear silencer, is the last box in your exhaust system before the tailpipe. Inside, a series of chambers and perforated tubes bounce the exhaust gases around to cancel out much of the engine’s noise before it leaves the car.

It works alongside the rest of the exhaust system, including the catalytic converter which sits nearer the engine and cleans the gases rather than quietening them.

Why Do Exhaust Back Boxes Fail?

Because the back box sits furthest from the engine, it runs cooler than the rest of the system, so water vapour in the exhaust condenses inside it and slowly rusts it from the inside out.

Short journeys make this worse, as the exhaust never gets hot enough to burn the moisture off, while road salt and knocks from speed bumps can damage the part from the outside.

How Much Does an Exhaust Back Box Replacement Cost?

Typical UK costs based on published industry estimates as of 25^th September 2026. Representative figures only as prices vary depending on your make and model, the parts used and your chosen garage. Enter your reg and postcode to compare instant prices from local garages for your exact car.

What Affects the Price?

• Your make and model. Back boxes for common small cars cost less than those for larger or performance models, especially those with twin tailpipes.

• How the box is fitted. On some cars the silencer bolts on as a separate part. On others it’s welded to the middle section of the exhaust from the factory, so the garage needs to cut the old one off and fit the new box with a clamp or joint.

• Genuine or aftermarket parts. Manufacturer parts usually cost more than good-quality aftermarket equivalents.

• Extra parts. Rusted clamps, rubber hangers and gaskets are often replaced at the same time.

Can You Repair an Exhaust Silencer Instead of Replacing It?

Yes, depending on the damage. A garage can often weld a small hole in an otherwise healthy box, while severe corrosion, split seams or baffles that have broken loose mean a replacement is more reliable option.

You can patch the issue with exhaust repair paste or bandage, but these are short-term solutions that rarely last: if the silencer is rusting from the inside, another hole will soon appear nearby.

Once your chosen garage has inspected your exhaust, they can tell you whether a repair or replacement makes the most sense.

Can You Drive with a Broken Back Box?

While you can usually drive your car a short distance to get it to a garage, we wouldn’t recommend it.

A leaking exhaust can let dangerous fumes into the car and potentially land you with a £2,500 fine and penalty points for contributing to an unroadworthy vehicle, so you should get the problem fixed as soon as possible.

Most importantly, a broken silencer can cause an MOT failure. Testers check for exhaust leaks, for noise that’s clearly louder than a similar car with a standard silencer and for loose parts of the system, any of which can cause your vehicle to fail.

If you don’t have time to arrange for a tow to a local garage, we work with a growing network of mobile mechanics who offer mobile exhaust repairs on your driveway or at your place of work to make your life more convenient.

Warning Signs Your Back Box Needs Replacing

• The exhaust sounds much louder or more like a roar than it used to

• A rattle from under the back of the car, which can mean the baffles inside the box have broken or a hanger has snapped

• A blowing, hissing or puffing sound from the rear of the car

• Visible rust, holes or split seams on the box

• The back box hanging lower than usual or knocking against the car

• A smell of exhaust fumes inside the car

Why Book with BookMyGarage?

• BMG-Verified garages across the UK. Local businesses that offer great value and consistently meet service standards. Look for the BMG-Verified badge to find the garages we’ve ensured meet our high standards for customer service, ratings and reliability.

• We Show the Full Picture. All up front: prices, reviews, availability and distance, so you can choose the right garage based on what matters most to you.

• Real Reviews. Genuine, verified feedback from drivers like you. Every review helps you book with confidence.

• No Upfront Payment. We won’t ask for any payment details when you book. Pay the garage directly once the work’s complete.*

• Compare & Book in Seconds. See your options side by side and choose the right garage for you. No jargon. No stress. No surprises.

• Support Local Garages. We connect drivers with quality local businesses that keep communities moving.

*Some mobile technicians (that come out to you) may require an upfront payment or commitment, please check this with them first.

These are just some of the reasons to choose BookMyGarage — enter your reg and postcode to compare exhaust back box replacement prices near you now.