In a quick summary, the process took me about two to three hours because I had to pull out the two second-row seats, thread holes in the floor, and make cuts in the carpet, with the help of another person. Cutting the two holes for the rear of the seat took a while because the floor under the carpet in the 6-seater XC90 has an additional layer of MDF underneath to reinforce the area for passengers walking to the third row (though I haven’t looked at the carpet in a 7-seater XC90 to compare). The conversion is very doable and I’m happy that stuff doesn’t fly from the cargo area to the front when braking and that there’s an armrest for second-row passengers.
Things I had to purchase/tools needed
As mentioned above, the holes for the middle seat are present but aren’t threaded, so you’ll need to buy a 10mm-1.50 tap to thread the holes. I bought the following tap and handle from Lowe’s, as well as a bottle of thread-cutting oil (I don’t know if oil was necessary since I was manually cutting the threads but figured it couldn’t hurt):
As mentioned in an earlier post, you’ll also need two of P/N 30624593 and two of P/N 999185. These bolts are identical to the ones already installed for the other two seats (the front bolts are interchangeable with the other front bolts and the rear bolts, with the washer, are interchangeable with the other rear bolts).
Additionally, I used a socket wrench (the bolt heads are different sizes, I think one was 13mm head and the other a 14mm but I don’t remember), a long and a short socket extension, nail polish to mark the hole locations, a drill to put a hole in the carpet, a Dremel to make a cutout for the rear hole of the seat rail, and a drywall saw, also to make a cutout for the rear hole of the seat rail.
The installation
First, I removed the second-row seats from the car. I didn’t disconnect the battery and had no issues. I found it useful to have the interior lights since I started the process in the early afternoon, finishing in the evening. That process is pretty straightforward, remove the four bolts on each seat. Before pulling the seats away, take care to disconnect the cable with the large grey connector (one per seat). I folded the seats down and lifted them out through the side doors. You’ll be left with this:
There are two plastic ducts on the floor that provide ventilation to the third row that you can pop out so they don’t get in the way.
On each seat, you’ll have to remove a trim piece that covers the rail, as seen in Post 103 of this thread:
Disconnect the green connector from the black one. I ended up ziptieing the reconnected wires to the inner side of the rail after removing the trim pieces, to keep them tidy and secure. After undoing the bolts, I wasn’t really sure how to remove the trim pieces so I pried them until they came off.
Edit: I originally removed these trim pieces from that post thinking they would cause interference with the other seats, but another user pointed out that they were able to install the seat without removing the pieces.
Back to the car, I began pulling up the carpet to access the mounting holes, making sure not to break any trim pieces. You’ll see two pairs of unthreaded holes, which you’ll have to thread. I filled a lab wash bottle with the cutting oil for easy dispensing. Initially, I used clamps to hold the carpet back but ended up having someone hold the carpet up instead, and was careful to wipe up any excess cutting oil so it wouldn’t stain the carpet. I following the instructions on the tap packaging, reversing a quarter turn when the tap started to bind to break chips. I dispensed oil before threading as well as every time after I broke the chips.
After using a paper towel to clean the oil and chips up, I threaded each bolt in and marked the top of each with red nail polish, so I could locate where the holes were to be drilled in the carpet. I used a utility knife to cut out a slot for the “pegs” of the seat rail to sit in the oval slots in the floor.
As previously mentioned, the rear holes are a bit trickier because the floor is reinforced on the model with a ~1/8″ layer of MDF and a ton of foam (I measured about 20mm thick) so I had to make a larger cutout for the rear holes to get the rail to contact with the metal subfloor. I started by drilling a regular hole to get an idea of where the cutout had to be. Initially, I was going to use longer 60mm bolts from the hardware store but realized that wouldn’t work because the rear of the rail would sit too high and the seat would be tilted forward. I measured the width of the rear of the rail to get an estimate of how big the cutout had to be, drew lines with a silver Sharpie on the carpet, and used a Dremel and drywall saw to make the cuts, with a piece of scrap lumber underneath to prevent damage. Note that using the Dremel will make things a bit smoky so I took breaks to make sure the carpet wouldn’t overheat too much.
I could have made my cuts a bit cleaner but was exhausted by this point and figured everything would be covered up anyway. I vacuumed all the debris, put the carpet and vents back and reconnected the wiring.
Here are some pictures of the final result:
This post should definitely help with the process!