E46 Complete Chassis Reinforcement Guide - K0441

Table of Contents:

I. Rear Subframe Removal

II. Rear Chassis Reinforcement Plates - K0117

III. Rear Sway Reinforcement - K0261

IV. RTAB Pocket Reinforcement - K0435

V. Front Subframe Reinforcement - K0238

Guide:

I. Rear Subframe Removal

The following steps can be found below:  Raising The Vehicle, Exhaust Removal,  Brake Caliper Removal,  Removing Rear Suspension, Disconnecting Driveshaft, Disconnecting Trailing Arms, Handbrake Cables, Removing Subframe

This article will cover the main points on removing an E46 rear subframe. This is a common practice for any E46 owner. Whether it be to replace worn out bushings, reinforce the subframe mounting points on the chassis, or repair cracks or tears in the unibody caused by years of hard-driving. Removing an E46 rear subframe isn't hard, but it can be time-consuming. This article will cover removing the entire subframe as a whole. This is the most effective method as it requires the least amount of work. It also benefits those doing it on jack stands as a simple floor jack can be used to remove the entire subframe and slide it out from under the car.

Raising The Vehicle

Required Tools

• Two Floor Jacks (one is acceptable)
• Four Jack Stands
• Mechanics Gloves
• 1/2" Electric Impact (Ratchet and Socket are fine)

Procedure

Step 1: Jack the rear of the vehicle up as high as you can. To do this you'll want to put the jack under the rear subframe on the section that wraps around the diff.

Step 2: Place jack stands under the rear side lift pads. Be sure to get them as high as possible while still being sturdy.

Step 3: Lower vehicle on to lift pads. Make sure the vehicle is secure and not rocking on uneven stands.

Step 4: Using both jacks at both front lift pads, evenly raise the vehicle until it is level with the rear jack stands

Step 5: Place the second set of jack stands under center frame rails at the front of the vehicle.

Step 6: Lower vehicle on to jack stands. Make sure the vehicle is secure and not rocking on uneven jack stands.

Step 7: Using 1/2" impact and socket remove rear wheels and place to the side.

Exhaust Removal

Required Tools

• 1/2" Impact
• 13mm Socket
• 17mm Socket
• 17mm Wrench
• Ratchet
• Extension

Procedure

Step 1: Remove eight 13mm bolts from the front skid plate using 1/2" impact and remove the skid plate from the vehicle.

Step 2: Using 1/2" impact, 17mm socket, and 17mm wrench unbolt the four bolts connecting the exhaust to the headers.

Step 3: Move to the rear of the vehicle and use a 13mm socket, extension, and impact to remove the four bolts on the rubber exhaust hangers and let the entire exhaust droop. 

Step 4: Move to the center of the vehicle and remove the eight 13mm bolts holding the center of the exhaust section, and carefully lower the entire exhaust system down.

Step 5: Slide exhaust out from under the vehicle and place somewhere out of the way.

Brake Caliper Removal

Required Tools

• 2 Long Flat Screwdrivers
• 3/8" Ratchet
• 7mm Allen Socket
• Zip ties or strong wire

Procedure

Step 1: Using a screwdriver remove the plastic cap from caliper dust covers

Step 2: Using one screwdriver, use one to apply pressure on the inside of the caliper anti-rattle clip and press out. Use second screwdriver to pry anti-rattle clip out of the caliper. 

Step 3: Using one screwdriver, insert it into caliper through to brake pad and pry brake pad back compressing caliper.

Step 4: Using the 7mm socket and 3/8" ratchet unbolt caliper from caliper bracket and remove caliper guide pins from the caliper.

Step 5: Slide calipers off of rotor and caliper bracket.

Step 6: Using zip ties or wire hang caliper bracket in a safe location away from the subframe

Removing Rear Suspension

Required Tools

• 1/2" Impact
• 18mm socket
• Jack

Step 1: Ensure the handbrake is disengaged.

Step 2: Place a jack under rear shock and raise jack to meet rear shock.

Step 3: Using 18mm socket and impact unbolt shock

Step 4: Slowly lower the jack until the rear spring can be removed.

Step 5 (Optional): In trunk go to rear shock towers and unbolt two 13mm nuts holding rear shocks.

Disconnecting Driveshaft

Required Tools

• 17mm Socket or E12 E-Torx Socket
• 10mm Socket
• 13mm Socket
• Extension
• 3/8" Ratchet
• 1/2" Impact
• Small/Medium Pry Bar

Step 1: Using an impact and a 10mm socket unbolt the heat shield covering the front subframe brace.

Step 2: Using Impact, 13mm, and 18mm socket unbolt front subframe brace. There will be two 18mm bolts and 4 13mm bolts.

Step 3: Take the E12 or 17mm socket and extension and unbolt the driveshaft from the input shaft on the differential. This will either be a six-bolt E12 or four-bolt 17mm.

Step 4: Using the pry bar insert it into the recess found on the outside edge of the driveshaft where it goes into the input shaft and pry the two flanges apart.

Step 5: Move the driveshaft out of the way so that it does not contact the subframe when removing.

Disconnecting Trailing Arms

Required Tools

• Jack
• 18mm Socket
• 1/2" Impact
• Extension

Step 1: Place a jack under the middle of trailing arm and support trailing arm from underneath.

Step 2: Use your impact or wrench, extension, and 18mm socket to unbolt the trailing arms from the body. There are three bolts per side.

Step 3: Lower the trailing arm and allow it to rest disconnected from the body.

Handbrake Cables

Required Tools

• Pocket Screwdriver or trim removal tool
• 10mm Socket
• 3/8 Ratchet
• Extension
• 10mm wrench

Step 1: Inside vehicle remover parking brake leather cover using pocket screwdriver or trim removal tool.

Step 2: Using a ratchet, extension, 10mm socket, and 10mm wrench unbolt the parking brake cables from the parking brake handle.

Step 3: Push parking brake cables into the parking brake cable tube as far as allowable. This will make lowering the subframe easier

Removing Subframe

Required Tools

• Two Floor Jacks
• 1/2" Impact
• 18mm Socket

Step 1: Use a floor jack to support the subframe at the front brace that surrounds the diff snout. 

Step 2: Use a second jack to support the subframe from the rear section of diff. This will equalize pressure on the subframe mounts so the subframe doesn't bind up on the studs in the chassis.  

Step 3: Using impact and 18mm socket unbolt the rear subframe nuts

Step 4: Carefully lower both jacks at the same speed and the subframe should drop with little to no effort. If the subframe hangs. Raise jacks back up and use a pry bar to help move the subframe down the studs.

*Be sure to lower the front and rear of the subframe in increments and carefully pull the parking brake cables out with the subframe.

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II. Rear Chassis Reinforcement Plates - K0117

Overview:

• Part Name: E46 BMW Rear Chassis Reinforcement Plates
• Part Number: K0117
• Part Page: https://www.garagistic.com/products/e46-bmw-rear-chassis-reinforcement-plates?_pos=3&_psq=e46-reinf&_ss=e&_v=1.0
• Difficulty Level: 10

Tools Required:

• Welder
• Wire wheel/brush to prep surfaces for welding
• Jack and jack stands
• Basic Ratchet and Socket Set
• Electric Impact
• Small Pick or Screwdriver

Installing Subframe reinforcement plates can be a daunting task for novice mechanics. As such we always recommend having a welding professional install these plates as they are welded on to structural parts of your chassis. This guide will go over preparation and placement of the brackets.

Installation Orientation:

As seen below the two identical plates are mounted at the front two subframe mounts and the two larger plates mount at the rear. They are designed to contour the body for ease of welding.

Before you begin this installation the entire rear end of the vehicle must be removed along with the fuel tank and evap parts including the charcoal canister. Below you will find a link to our subframe removal guide.

https://garagistic.zendesk.com/hc/en-us/articles/360052930933-E46-Rear-Subframe-Removal-Guide

Fuel Tank Removal

Step 1:

Before the fuel tank can be removed you'll first need to remove the rear seat bench. This can be done in a matter of seconds by simply lifting the rear seat upwards. Some effort will be required to release it from its clips.

Step 2:

Once the seat has been removed you will find two large black metal covers. Unscrew the 4 10mm Bolts from each and move them to the side.

Step 3:

Below the covers, you will find the fuel tank lines and wiring for the fuel pump and sending unit. Release the electrical connectors from both and then carefully remove each hose from the fuel pump and sending unit.

Step 4:

Next go under the vehicle. You will need to use a 10mm socket to release the nut holding then filler neck to the body. Once this is done use a screwdriver to release the hose clamps on the rubber hose that connects the filler neck to the fuel tank.

Step 5:

Once the filler neck is released you can lower the tank. To do so support the tank from underneath with a friend or a pair of jacks. Unbolt the 3 13mm bolts holding the tank to the body. Release the fuel tank straps by rotating the down and then pushing them up towards the top of the car.

Step 6:

Begin lowering the tank and from the front side keep an eye on the lines that are attached to the tank. Some of them will need to be released and moved out of the way as the tank is lowered. Once the tank is lowered. If you are on jack stands you will be able to move it out of the way to clean and weld your reinforcement plates in.

Cleaning and Prepping Plates

Step 1:

Before installing your subframe reinforcement plates you will first need to prepare or clean the metal you are welding to. Below are a few tools you can use to help you clean everything. For this guide we used a seam sealer removal wheel and a wire brush on a drill. Roloc wheels are another excellent way to remove paint and underbody coating.

Step 2:

Using the seams sealer removal wheel pictured far right above begin to clean the metal around each subframe pickup point. This is done not only to prepare the metal but to inspect for any cracks that may not yet be visible as sometimes they can be hidden under seam sealer or underbody coatings. See below reference photos for an idea of how much material you should clean. It's always good to go a little further than the plates. This makes welding easier and helps find cracks!

 Step 3:

Once you have cleaned the areas surrounding the plates with the removal wheel. Take your wire wheel and go over everything again. This will help ensure no paint or other unwanted materials are left on the body. These can ruin a good weld and make things a little more difficult for you or your welder.

Step 4:

Take your wire wheel and clean all areas on the reinforcement plates that are to be welded. This removed any machining oils or coatings that may be on the plates and will help ensure you get the cleanest welds possible.

Step 5:

Using the supplied hardware and/or the bolts from the trailing arm brackets, bolt the plates up to the body. Make sure to line them up as close as possible to the chassis leaving minimal gaps.

Step 6:

Once everything is in place you may begin welding! Once everything is in allow the metal to cool before applying a coat of paint to the bare metal. Rust-O-Leum High-Performance paints are a great product to cover these areas. It is very chip-resistant and won't crack over time being in a high-stress area.

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III. Rear Sway Reinforcement - K0261

*Professional welder is recommended when installing reinforcement plates*

Some plates will need to be bent to fit your application. Using a vise and hammer will work perfectly. Always use safety glasses and other proper safety workwear

Quick tip: Hold piece in its proper position and use a sharpie to make its position to use a s a reference point. Keep in mind no two subframes are the same as they have gone through different conditions

Thoroughly clean the area of any dirt, oil, grease, and grime of any kind. Acetone works well for cleaning
Hold reinforcement pieces in its designated position and tack it in place
Clamping pliers can be used as well to hold certain plates in place
Use nut and bolt on plates that can be bolted down to help center the plates properly
Front subframe balljoint reinforment plates will need to be centered to ball joint but favoring the slots to be even with the subframe so it can be bent properly. Tack the plate in place then with a hammer fold the edges down so it takes form of the subframe

Other reinforcement pieces will have too tapped into place using a hammer to make sure you have a flush fitment. 
Double check that your reinforcements are properly positioned before fully welding
If attempting to weld yourself, we recommended using a mig welder as it is easier to use

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IV. RTAB Pocket Reinforcements - K0435

The two Rear Trailing Arm Bushing (RTAB) Pocket Reinforcement plates in this kit can be welded in place to reinforce the floor at this 3-bolt RTAB mount in the chassis, as shown. This can be added to both E46 non-M and M3 models.

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V. Front Subframe Reinforcement - K0238

*Professional welder is recommended when installing reinforcement plates*

Some plates will need to be bent to fit your application. Using a vise and hammer will work perfectly. Always use safety glasses and other proper safety workwear

Quick tip: Hold piece in its proper position and use a sharpie to make its position to use a s a reference point
Thoroughly clean the area of any dirt, oil, grease, and grime of any kind. Acetone works well for cleaning
Hold reinforcement pieces in its designated position and tack it in place
Clamping pliers can be used as well to hold certain plates in place
Use nut and bolt on plates that can be bolted down to help center the plates properly
Front subframe balljoint reinforment plates will need to be centered to ball joint but favoring the slots to be even with the subframe so it can be bent properly. Tack the plate in place then with a hammer fold the edges down so it takes form of the subframe
Double check that your reinforcements are properly positioned before fully welding
If attempting to weld yourself, we recommended using a mig welder as it is easier to use


Front Subframe