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Old 01-31-2012, 01:57 PM
Bread Bread is offline
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Curt 13070 receiver install - the right way

This weekend I installed a Curt receiver on our ’02 4.6is and found some things I’d like to share. Yes, it’s not a hitch. It’s a receiver J The included instructions were essentially crap (wrong wrench sizes, wrong hardware quantities, and just very vague in general), and I was shocked how they propose it should be installed. I’ve emailed the company regarding their poor, and in my opinion unsafe installation method. For some background on me, I’ve been a Millwright and industrial maintenance technician for the last 10 years. I troubleshoot and repair failed equipment for a living. Not to mention being a motor-head and wrenching on vehicles before I could even drive.

The Curt receiver itself is a well made fabrication. The welds look good, and the mounting plate is a heavy ¼”. Despite having a couple chips from shipping, the finish is nice as well. It is my second choice over the factory receiver, but my g/f’s first choice since she paid for it J The DrawTite hitch with the drop bar is garbage. It does not bolt to the reinforced unibody rails, but rather the weaker center brace. I would never touch one. The Curt receiver bolts directly to the reinforced rails and brackets on the unibody, and is only second to the factory hitch because it does not also incorporate the center brace like the factory receiver does. This is likely the reason the tow rating is reduced from the vehicle max of 6000lbs to 5000lbs. The rating makes no difference to me as we only purchased this receiver to mount a Softride bike/ski rack. And we also won’t need any wiring. When I want to tow I use my F350, and save the X5 for haulin’ ass up to the slopes. However, that doesn’t mean that a future owner won’t try to hook a trailer up, so I want it to be right!

Oh, and it makes no difference if you tow at 80 or 90mph as I’ve seen some testimonials report. That’s so annoying because speed is irrelevant. The major stresses placed on the receiver are during braking and accelerating. And the 4.6is can brake and accelerate pretty damn hard!

Just some basic disassembly notes before getting to the important stuff. We have the optional slide out cargo tray on our ‘02, so the pictures are specific to our model. I say that because from what I’ve read that there are also some differences in the bumper bracket mounting hardware from year to year. YMMV.

Step1: Prop up the cargo tray, and remove the carpeted floor trim panels, one on each side secured with three Phillips screws. Slide the trim towards the center to release the two catches underneath and remove. Also remove the cover panels on each sidewall which conceal the DVD/NAV system and speakers.


Step 2: Remove the plastic trays on each side with a 10mm socket driver. Also remove the wheel chock holder held in with the same plastic nuts.


Step 3: Unplug the PDC harness at the passenger side rear corner. Rotate the cam lever to release, and push the grommet and plug through the hole in the body.


Step 4: At the lower rear of each fender liner there are a couple small screws. On each side remove the bottom screw only with an 8mm socket.

Step 5: Release the 4 tabs at the bottom of the rear bumper skirt, where it attaches to the spare tire pan. It takes some finagling to get them loose. (NOTE: In this pic I have already removed the plastic cover that resides just behind the tabs).


To remove the bumper, you now just need to remove the two T55 bolts above the exhaust tips. If you have a 3.0 you can probably get to those bolts at this point and skip to step 8. If you have a 4.4 or 4.6is with the wide exhaust tips you’ll need to remove some more stuff . Continue to the next step.

Step 6: Underneath the bumper again, remove the plastic cover in the center of the bumper. Remove the three Phillips screws, and then pry/push the plastic tabs on the sides inwards (towards the center) to remove the piece. Here it is removed so you can see what those tabs look like. The arrows show which direction to push.


Step 7: Loosen the (2ea) nuts per side on the REAR muffler hangers with a 13mm socket and extension (pictured with the bumper off for clarity. Yours is not off yet). You don’t need to remove the hangers forward of the muffler. You also don’t need the jack stands at this point as you want the exhaust tips to drop all the way down in the opening in the body to access the bolts above. They will be put back under when the bumper is removed and installed.


Step 8: Now you should be able to remove the two T55 bolts securing the rear bumper brace. I still had to use a u-joint to reach up there. These were really damn tight, and my T55 socket is a 3/8” drive. So I put a longer 3/8” drive breaker on it to get them loose. I also put a rag, and a piece of cardboard on the exhaust tip to protect it from my wrench.


Step 9: Support the exhaust tips back into place either with jack stands, or by simply bolting them back up. Pull the bumper straight back and off. The fender liner tends to hang up on the bumper trim on the 4.6is, so it takes a good tug to break them free. Be prepared, it’s heavy! I cleared my work area first so I had a clear path to walk outside and set the bumper down on the grass. Also make sure the PDC wire doesn’t get caught as the bumper comes off.


Step 10: Remove the bumper mounts/shock absorbers via the three nuts located inside. Then remove the rear brace secured with (8ea) T50 bolts on the face, and (2ea) bolts underneath with a 13mm socket.


Now the fun stuff. Curt provides (2ea) ½-13 bolts with nice serrated flange nuts to be installed in the top two holes of the hitch. They also provide (2ea) 7/16-14 bolts and flange nuts to install in the bottom two holes. These really just locate the receiver and serve no structural purpose due to the thin sheet metal they are bolted too. For the other two main structural mounting holes per side Curt instructs to re-use the tiny 8mm studs that were used to hold up the rear bumper. This is lacking in a major way! Those 8mm studs are designed to hold up the plastic bumper, not pull 5000lbs (as Curt rates their receiver). The only bolts which are rated to carry load are the two they have you install at the very top of the receiver. Their setup is actually fine for braking, when the receiver is pressed against the body and the top two bolts stop the rotational force which is pushing in on the bottom. But during acceleration all of the stress is pulling on those tiny bottom studs which are not rated for any kind of heavy load. So after shaking my head in disgust for a few minutes in my garage, I threw the instructions in the trash, bolted the mufflers back up and headed off to the hardware store. I hate driving this thing as it is with the winter wheels/tires on it, but with the bumper missing people look at me like I’ve carelessly destroyed this thing with my lack of driving skill J


So this is what I did. Instead of only punching out the stop stud, I punched out all three of them, and drilled out all three holes to accept ½-13 bolts (9/16” holes). Enlarging the holes was easy using a step bit with some cutting fluid. Keep the rpms relatively low. Drilling these bumper brackets is the only modification required. The holes in the chassis and the receiver are already large enough to clear larger bolts. I have no idea why Curt wouldn’t have just instructed to replace all of them. Makes absolutely no sense to me whatsoever.


I picked up some grade-8 bolts, grade-8 fender washers (larger diameter than standard washers), and grade-8 stover/pinched flange nuts which are self-locking and therefore don’t need to be serrated under the flange. They will never loosen up. I chose grade-8 bolts because they don’t stretch like the grade-5, but in retrospect grade-5 would be just fine. I was angry and went overboard Pictured below from R to L is the factory stud, the bolt Curt includes, and the grade 8 bolts I used.


This hardware upgrade cost me $20, and only a few extra minutes to install. After putting the receiver in place and loosely installing all of the bolts, I snugged all of them, then fully tightened the lower 7/16” bolts to align everything. Then I hit the rest of them with my impact gun. The large washers are installed INSIDE the chassis, directly against the sheet metal to help distribute the load over a wider surface area.

The large fender washers I purchased were too big to use in the uppermost two holes. They ran into the radius in the body and would not sit flat. I could have ground down the side of one of the washers to create clearance. But instead I decided to use the flange nut that came with the Curt hardware kit, which just clears.


Here the receiver is fully installed with the 1/2-13 hardware.


I’m 100% confident with this modified installation. I wouldn’t hesitate to tow up to the 6000lb vehicle chassis rating if I needed to. The receiver looks clean, and required no modifications to the structure or bumper of the vehicle. We purchased it for $140 off Amazon, and I would recommend it to anyone when installed with the proper ½-13 hardware in all 6 mounting holes.


Extra/upgrade hardware list:
(6ea) ½-13 x 1.75” long bolts
(4ea) ½-13 stover/pinched flange nuts (self-locking)
(4ea) ½” fender washers

Tools Required:
T55 socket
T50 socket
13mm socket
10mm socket or nut driver
8mm socket
9/16” socket
9/16” open ended wrench
#2 Phillips screw driver
Needle nose pliers (for getting those plastic nuts back in their holes)
3/8” ratchet
3/8” drive extension
3/8” drive U-joint
¾” sockets (2ea) (one impact, one steel)
¾” ratchet
½” drive breaker bar
½” drive impact gun if you have one

Last edited by Bread; 01-31-2012 at 02:20 PM.
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