Introduction

Upgrading the exhaust on your Mercedes‑AMG GT is one of the most effective ways to unlock its true character. The Fabspeed exhaust system is a popular choice among enthusiasts because it delivers a richer, more aggressive note while shedding significant weight compared to the factory system. This guide provides a complete, step‑by‑step walkthrough for installing the Fabspeed exhaust on your AMG GT. Whether you’re a seasoned DIYer or a first‑time buyer, following these detailed instructions will help you achieve a clean, professional‑grade installation and avoid common pitfalls.

Before you begin, understand that working under a vehicle requires care and attention. Allow yourself a full afternoon for the job—rushing can lead to misalignment, stripped bolts, or damage to the new components. With the right preparation and tools, you’ll be rewarded with a noticeable improvement in both sound and performance.

Tools and Materials

Gathering everything you need before you lift the car prevents frustrating delays. The following list covers the essential tools and supplies for the Fabspeed exhaust installation on the AMG GT.

  • Fabspeed exhaust system (make sure you have the correct variant for your AMG GT model – standard, S, C, R, or GT63 – as hanger positions and pipe diameters differ)
  • Socket set – metric sockets from 8 mm to 19 mm; a 13 mm and a 15 mm are most common for exhaust bolts
  • Wrench set – combination wrenches in the same metric sizes; a flex‑head or ratcheting wrenches can help in tight spots
  • Torque wrench (ft‑lb / Nm) for tightening hardware to spec
  • Jack and jack stands (rated for at least 2 tons; a low‑profile floor jack is ideal)
  • Penetrating oil (e.g., WD‑40 Specialist, PB Blaster) for stuck fasteners
  • Anti‑seize compound – apply to reusable clamps and bolts during reassembly
  • Flathead screwdriver and trim removal tool for releasing rubber hangers
  • Shop rags and safety glasses
  • Mechanics gloves – leather or nitrile coated, for grip and protection
  • Tubing or pipe lubricant (optional) – helps slide rubber hangers over the new pipe nipples
  • Digital camera or phone – take photos of the original exhaust routing for reference

If you plan to reuse the factory clamps, check that they haven’t been compromised by corrosion. Many installers prefer to use new stainless steel clamps (often included with the Fabspeed system) for a tighter, longer‑lasting seal. Also, keep a small container of high‑temperature silicone sealant handy – some builders apply a thin film to the ball‑joint flanges to ensure a leak‑free connection.

Safety and Preparation

Choose the Right Work Area

Work on a flat, level concrete or asphalt surface. A surface covered with gravel or loose dirt can allow a jack stand to sink or shift. Ensure the area is well‑lit and that you have enough overhead space to move a jack handle freely.

Lifting the Car Correctly

The AMG GT has designated jack points at the four corners, clearly indicated by small arrows or triangles on the rocker panels. Position the jack saddle under the front jack pad first, raise the chassis, and place a jack stand under the front lift point (the reinforced area just behind the front wheel well). Repeat for the rear. Always lower the vehicle onto the stands so the weight is supported, then chock the remaining wheels. Never work under a car supported only by a hydraulic jack.

Let the Exhaust Cool

If you’ve just driven the car, wait at least two hours for the exhaust and catalytic converters to cool to ambient temperature. The factory exhaust system can reach several hundred degrees, and hot metal can cause severe burns. Touching a hot O₂ sensor or catalytic converter can also damage those components.

Protect Yourself

Wear safety glasses at all times. Falling debris, splattered penetrating oil, or spring‑back from a hanger can injure your eyes. Gloves are essential – not only for heat protection but also to prevent cuts from sharp edges on the underbody panels or exhaust flanges.

Removing the Stock Exhaust

Dismantle the Underbody Panels

The AMG GT has large aerodynamic underbody trays that must be removed to access the exhaust. Using a 8 mm or 10 mm socket, remove the screws and push‑clips that secure the front and rear panels. Keep the hardware organized – you’ll reuse most of it. Set the panels aside in a clean area.

Disconnect the O₂ Sensors

Carefully unplug the oxygen sensor connectors on both the upstream (pre‑cat) and downstream (post‑cat) sensors. Use a flathead screwdriver to release the locking tab, then pull the connectors apart. Avoid yanking the wires. If the sensors are stubborn, a small amount of penetrating oil on the connector can help. Label each connector with tape to avoid mix‑up during reinstallation.

Unbolt the Stock Exhaust

Begin at the rear of the system. Use a 13 mm socket to remove the bolts connecting the rear muffler section to the mid‑pipe (or connecting pipe). There are typically two bolts per flange; often they are studs with nuts. Apply penetrating oil and let it soak for a few minutes before turning.

Next, remove the bolts at the mid‑pipe to catalytic converter connection. The AMG GT uses a ball‑joint style clamp at this location. Loosen the two nuts (usually 15 mm) until the clamp separates. Do not force the pipe apart – it may require gently rocking the exhaust to break the seal.

Slide the exhaust sections off the rubber hangers. Rubber hangers are retained by a metal tab on the pipe. Use a screwdriver to pry the hanger over the tab, or apply a small amount of lubricant to the rubber to ease removal. Some hangers might require twisting the pipe to free them.

Removing the Entire System (One Piece vs. Two)

Depending on your AMG GT year and model, you can either slide the exhaust out as one assembly (rear section only) or dissasemble it into two parts. The Fabspeed system replaces the axle‑back portion (from the mid‑pipe back) for most applications. If you are installing a full cat‑back system, you may need to unbolt the mid‑pipe as well. Here, we assume the cat‑back installation, leaving the catalytic converters in place.

Once disconnected from the hangers and flanges, carefully maneuver the exhaust out from under the car. Have a helper support the front section as you slide it rearward. The factory exhaust is heavy – approximately 30‑40 lbs – so use your legs and avoid twisting your back.

Installing the Fabspeed Exhaust

Prepare the New System

Inspect the Fabspeed exhaust for any shipping damage. Compare the gaskets, clamps, and hanger locations against the original system. Apply a thin layer of anti‑seize to the threads of all bolts and studs. This will make future removal easier and prevent galling on stainless steel fasteners.

Position the Exhaust Under the Car

Slide the Fabspeed system into place from the rear. If the system comes in two pieces (e.g., separate muffler and connecting pipe), loosely assemble the joint before lifting everything into position. Support the muffler section on a jack or with a helper – the Fabspeed system is lighter than stock, but still awkward to fit solo.

Connect to the Mid‑Pipe (or Cats)

Insert the Fabspeed inlet pipe into the factory ball‑joint flange (or into the provided mating flange if you have a full replacement mid‑pipe). Align the clamp so it seats evenly. Hand‑tighten the two clamp nuts, then torque to 40 ft‑lb (54 Nm) if using the factory clamp, or follow the Fabspeed instruction sheet for their supplied clamp. Do not fully tighten until all sections are aligned and the tips are positioned correctly.

Attach the Hangers

Slide the rubber hangers over the new pipe tabs. A dab of silicone lubricant or dish soap will help them slip on. Ensure each hanger is fully seated – the metal tab should be captured inside the center of the rubber isolator. If the new system uses different hanger positions, verify they align with the body‑mounted hanger brackets. Minor adjustments can be made by loosening the clamp and rotating the pipe section.

Mount the Tips and Final Alignment

If your Fabspeed system comes with separate exhaust tips, attach them now using the supplied set screws or clamp. Position the tips so they sit centered in the bumper cutouts and are relatively parallel to the ground. A small gap between the tip and the bumper trim (approx. 1/4 inch) is ideal – this prevents rattling and allows for heat expansion. Tighten the tip hardware securely, but avoid overtightening that could dent the tip.

Tighten All Connections

Once the entire system is aligned and hanging freely without touching the underbody or heat shields, start tightening all bolts and clamps from front to rear. Use a torque wrench: mid‑pipe flanges to 35‑40 ft‑lb (47‑54 Nm), muffler inlet clamps to 30‑35 ft‑lb (41‑47 Nm), and any V‑band clamps to 55‑65 in‑lb (6.2‑7.3 Nm) if applicable. Do not exceed the manufacturer’s recommendations.

Reconnect O₂ Sensors

Plug the O₂ sensor connectors back into the harnesses. Ensure the latches click. Tuck the wiring away from moving parts and exhaust heat – use zip ties to secure any loose harness to the chassis. Avoid routing wires over sharp edges or near the propeller shaft.

Post‑Installation Checks

Visual Inspection

Lay under the car with a flashlight. Check that the exhaust does not contact the frame, brake lines, fuel lines, or any heat shields. The pipes should have at least 1/2 inch clearance from all chassis components. Rotate the steering lock‑to‑lock to ensure the exhaust does not interfere with the steering rack.

Leak Test

Start the engine cold and let it idle. Place your hand near each joint (flange, clamp, hanger connection) to feel for air pulses. Alternatively, use a piece of cotton string or a thin rag – if it’s blown away, you have a leak. Apply high‑temperature silicone sealant to any leaking ball‑joint connections after retightening, or replace the gasket.

Sound and Smoke Check

Listen for any rattles, hisses, or drone. The Fabspeed system should produce a deep, refined tone at idle and a more aggressive note under hard acceleration. If you hear metallic rattling, check tip clearance or hanger alignment. Rev the engine to 2000‑3000 RPM and watch for smoke from the joints – white smoke indicates a leak; blue or black smoke from the pipe tip is normal during the first few heat cycles.

Check Engine Light (CEL) and OBD‑II

Some AMG GT models will throw a CEL due to lowered exhaust backpressure affecting the oxygen sensor readings. This is more common on cat‑back systems than axle‑backs, but can happen. If your CEL illuminates, have the codes read (likely P0420 or similar). Many aftermarket exhausts include an O₂ spacer (mini‑cat) to prevent this. If you experience persistent CELs, consider an ECU tune from a reputable shop to recalibrate the fuel trims and disable the secondary O₂ sensor monitoring. Fabspeed’s official product page often includes tuning recommendations for the AMG GT.

Tuning and Performance Considerations

Weight Savings and Throttle Response

The Fabspeed exhaust saved approximately 15‑20 lbs over the factory system. This reduction in unsprung weight (along with lowered backpressure) can improve throttle response, especially in mid‑range RPM. You may notice a slight increase in horsepower (5‑10 hp) when paired with a proper tune, but the primary benefit is the enhanced sound character.

Drone and Comfort

Some AMG GT models with the AMG Performance Exhaust (active valves) will retain the valve functionality when using the Fabspeed system with the proper valve kit. Closed valves produce a quiet, almost stock sound for highway cruising – open valves give the raucous Fabspeed tone. If you have a non‑valved system, expect a constant increase in cabin noise, which some owners find exhilarating and others tiring on long trips.

Warranty and Emissions

Installing an aftermarket exhaust will not void your entire vehicle warranty; however, Mercedes may deny claims directly related to the modification (e.g., a failed O₂ sensor caused by extreme heat transfer). Keep your stock parts to revert to factory if needed. The Fabspeed system is designed to be emissions‑legal for most states, but check local laws – some areas require catalytic converters to remain in the stock location.

For official torque specifications for factory exhaust bolts, consult the Mercedes‑Benz StarTekInfo portal or your model’s service manual. Many AMG GT owners also share installation experiences on BenzWorld AMG GT forums – a valuable resource for troubleshooting model‑specific quirks.

Conclusion

Installing the Fabspeed exhaust on your AMG GT is a rewarding weekend project that dramatically transforms the car’s acoustic character without sacrificing build quality. By following this detailed guide – from proper lifting and O₂ sensor handling to alignment and torque specs – you ensure a clean, leak‑free install that will provide years of enjoyment. The result is a more visceral driving experience: a deep, aggressive note that pays homage to the AMG GT’s racing pedigree while still being daily‑drivable. Take your time, respect the hardware, and you’ll be rewarded every time you press the start button.