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Trailer Hitch Install on RWD e46 Sport Wagon - Part I

Discussion in 'E46 (1999-2006)' started by eblue540, Apr 18, 2010.

    • Member

    eblue540 Fourth Gen Bimmers

    Post Count: 291
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    Disclaimer (Sorry to be obnoxious with this right up front, but you gotta do this nowadays): I am sharing my story and information in hopes that this will help others interested in doing the same thing to their car. I guarantee nothing; I do not guarantee that what I did will come out the same way on your car - no reason it shouldn't, but if it doesn't, that will be your fault, not mine. If you undertake to do this project on your car, consult the information provided by the manufacturers involved and be guided by them. If you do mess something up on your car doing this project, that is not my responsibility.

    Also, since this site only allows 8 images per post, I am going to have to break this into 2 or 3 posts. Sorry, not my rules, but I think the images help a lot, so I'm puttin' em in.

    My 2002 325 iT Sport wagon is a veritable Swiss army knife in the car world. This is not an SUV, but it is possible to get incredible utility from this vehicle which is sporty to drive, compact, efficient and looks great.

    I happen to have a 400 lbs aluminum utility trailer. My already amazing car will be even more so if it has a Class 1 receiver hitch. Class 1 means it can tow up to 2000 lbs and can carry a "tongue" weight of up to 300 lbs. In this post, I will detail the mechanical installation of the receiver hitch which I purchased on-line from http://www.hitchesonline.com .
    This site is well set up to hook you up with the correct receiver for installation into your particular car by year and body style. The hitch I purchased was manufactured by Curt Manufacturing

    . I ended up communicating with Mark, the application engineer at Curt when I ran into a couple of issues with my install. Mark's assistance was extremely responsive and addressed my issues perfectly - more on that below.

    Here is the patient, my '02 325 Sport wagon:

    [IMG]

    Five Speed, Rear Wheel drive, Baseball glove brown leather interior, Sport package, not Silver or Black or any shade in between. This car took me about 3 years to find and it replaced a 1993 VW Passat GLX VR6 5 speed wagon which was also tow hitch equipped.

    Here is the receiver hitch:

    [IMG]

    It essentially bolts to the bottom and rear of the underside of the spare tire well with backing plates located inside the tire well.

    Here are the backing plates:

    [IMG]

    Here is the receiver with the backing plates positioned as they will be located when installed; just imagine the sheet metal of the tire well between the receiver that the backing plates!

    [IMG]

    By now, you are saying to yourself (as I did when I first looked into this install):

    "that hitch is great and all, but you have to drill the sheet metal and once you do, they are going to begin to rust immediately and in a few years, you are going to yank that receiver right the heck out of those rusty holes in bottom of the tire well".

    I don't want that so I did not start this installation until I had a strategy to completely seal the drilled sheet metal. I did not want to compromise the structural integrity of the car down the road. For a solution, I spoke to Mark, the application engineer at Curt, who manufacture the receiver hitch kit, and I asked him what he recommended to absolutely seal the install. He had an immediate answer: Use GE Waterproof Silicone. When you are inserting the fasteners, load the holes up with the stuff, tighten the fasteners, let it cure and you will have a water tight seal that will remain intact, since there will be no movement to dislodge the seal once the fasteners are torqued down. To add a "belt to these suspenders", I decided to primer-paint the drilled holes as well, adding another barrier to corrosive liquid making contact with my German sheet metal's vulnerable drilled edges.

    Armed with this plan, I moved ahead with the installation.

    This installation starts with removing the floor, spare tire cover and spare tire from the rear cargo area:

    [IMG]


    Now, place the rear of your car safely on jack stands - Never work under a car supported by solely by a jack. Get up high enough that you can easily work under the rear of the car:

    [IMG]

    Next, the two curved backing plates are located 9 ¾" inches apart in the reinforcing corrugations of the sheet metal inside the rear wall of the spare tire well, long side vertical, short side horizontal. Measure carefully, and use a hammer behind an awl or nail to punch a small hole in the four carriage bolt hole locations on the backing plates. Next drill the holes using the punched holes to pilot your drill bit. Remember to start with a small drill bit and increase the size of the holes until the holes are large enough to just pass the carriage bolts through them. Push the four carriage bolts through the backing plate holes and through the sheet metal you just drilled

    Now, use your floor jack to raise and support the receiver adapter, taking care to align the holes in it with the carriage bolts now protruding from the bottom of the tire well:

    [IMG]

    Keep the forward portion of the adapter supported against the bottom of the tire well, and put the nuts of the four carriage bolts at the rear.

    The two carriage bolts that go into the rear wall of the tire well are now protruding into the space behind the bumper fascia. To get the nuts on these installed, you can pull the bottom edge of the flexible bumper fascia from under the car just enough the get your arm and a wrench up with a nut. It requires a skinny arm and a bit of patience as you can only turn the nuts a little at a time. If you have a fat arm, or no patience, you can remove the bumper fascia and get easy access.

    With the four carriage bolts in and somewhat tight, use the four holes at the front portion of the adapter as a template and use you awl again to mark and punch four holes for the forward straight adapter plates. You will punch these holes from under the car unlike the first four which you punched from inside the tire well.

    Drill these as you did the rear holes (they are smaller). Insert the bolts through the top of the straight backing plates, through the freshly drilled sheet metal and through the front holes in the receiver. Tighten up the bolts from under the car to confirm that everything fits. When it is all done, here's what it looks like from underneath:

    [IMG]

    If you live somewhere that it never rains and where cars never rust, you can just torque all eight bolts up and be done with the install. If you are not living in such a place, we need to take protective measures - remove all the fasteners, brackets and plates.

    END OF PART I - SEE OTHER POST FOR PART II
    • Member

    eblue540 Fourth Gen Bimmers

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    Trailer Hitch Install on RWD e46 Sport Wagon - Part II

    PART II (SEE PART I TOO)

    You now have eight raw edged holes in your car and you need to protect them from the corrosives that constantly attach your car:

    [IMG]

    Start by masking off around the eight holes leaving a ¼" margin clear around the holes. You don't have to do this, but I like a neat job and I don't think overspray inside my spare tire well counts as a neat job. Once the taping is complete, I used two coats of rust resistant primer from a rattle can. I applied from both inside and from underneath to be sure that all bare metal was at least double-coated. Allow to dry, remove the masking.

    Here is where it gets messy - literally. This is the Silicone product you wan to use:

    [IMG]

    Place the backing plates into position and apply a liberal blob of Silicone:
    [IMG]

    Insert the fasteners and immediately tighten them. It will be messy. You will capture and re-smear a bunch of the Silicone when you go under the car to tighten the nuts. The rear facing carriage bolts are the worst - the Silicone makes turning them stiff and slow, while your skinny arm is up under the bumper fascia. Be persistent and get them fully tight. Repeat with the front portion of the receiver - lots of Silicone into the holes. Once you have all eight fasteners fully tight. Go back and really tighten them down. Don't worry about wiping excess Silicone away. It is there to seal everything, and it will also act like a thread locker to help keep the fasteners from backing out.

    You job is done!

    As you can see, once installed, the receiver is pretty stealthy. It does not mar the appearance of the rear of the car and cannot even be seen until you stoop down at the rear of the car:

    [IMG]

    [IMG]


    I did have a small issue with the "Ball mount" which originally came with the kit for my car. Seems that the sport package version of the 325 wagon adds a lip to the lower rear edge of the bumper fascia, which is not present on non-sport pack cars. The original ball mount was making hard contact with this lip when mounted as shown here:

    [IMG]


    This type of contact will result in damaged paint and worse to both the bumper and to the ball mount itself in pretty short order. I discussed this issue with Mark at Curt Manufacturing. Mark authorized his firm to send me a different ball mount, part number D-231:

    [IMG]

    The D-231 ball mount is longer and has a slightly higher rise than the one which came with the receiver kit, but it is a perfect fit:

    [IMG]

    If you have a 325 wagon, I highly recommend this mod. Took me about an hour to do.

    Next up: The lights, the electrical installation which gets the trailer lights going. Coming soon!

    Chris
    • Member

    lcjhnsn

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    I'm going to have to consider doing this to my 2003 Touring. Thanks for sharing.

    But those are pretty stout bolts going through the spare tire well sheetmetal. It looks like there is a pretty substantial strength disparity between the fasteners and the sheetmetal they go through.
    • Member

    eblue540 Fourth Gen Bimmers

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    The strength of this arrangement...

    comes from the clamping of the sheet metal between the backing plates and the receiver hitch. When the load is distributed into the sheetmetal by the plates, rather than concentrated at the bolts, the sheet metal can supprt the load of a class I traler set up.

    Just stay within the class I load guidelines and don't let anyone rear end you with a trailer attached and this should work out. I ran this arrangement on my previous VE Passat wagon and had no issues at all.

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