DIY: 60/40 Split Seat Install (some welding required)

[CTScott]

I was fortunate enough to recently acquire a 60/40 split rear seat as a swap for the rear bench seat in one of my 2008 Yaris. In another thread (http://www.yarisworld.com/forums/showthread.php?t=42579), I described the process of installing my bench in AuxMike's Yaris. On his we had to drill two holes in the floor to expose threaded inserts, where the seatbelt buckles would mount.

When we did the swap, I was more concerned about my seat fitting in his car, so I just took a quick peek at the holes and thought that everything was there to install the split rear seat. Upon closer inspection I found that I would have to drill a total of 5 holes to expose threaded inserts. Three along the bottom of the front of the seat, and two at the front of center of the seat rails. After drilling the first of the seat rail holes, I realized that a threaded insert was not present under the floor. So, a simple bolt-in install turned into a remove the gas tank and weld in inserts job.


The first step is to mark where the holes need to be drilled. Set the seat in place, insert bolts into the existing holes to align it, and then mark the missing holes:


Drill the holes. I prefer to drill a small initial hole to verify centering on the insert, and then drill the hole a bit larger than the threads. I used a 5/8" drill bit. Because the threaded inserts are recessed below the floor, you can easily drill the holes without damaging the threads.


After drilling the first of the center seat rail holes, I noticed the lack of a threaded insert and a second layer of sheet metal about 1" below the floor layer. I decided to drop the gas tank to see if I could weld a M10 x 1.25 nut to the bottom of the floor. Dropping the tank requires removing the access panel above the tank, disconnecting the electrical connector (and then running the car until it dies to depressurize the fuel system), disconnecting the vent pipe, and disconnecting the fuel line.








I find the tank easier to handle empty, so I remove the filler hose by loosening the hose clamp and pulling it off. Then, I siphon as much gas as possible from the tank.


With the tank empty disconnect the small vent line via the yellow sleeved connector above the filler on the tank, and then remove the heat shield covering one corner of the tank, by removing the 10mm nut and bolt.






Next, the four 12mm bolts are removed from the four corners of the tank to free it.



With the tank removed, I realized that I did not have access to weld a threaded insert to the bottom of the floor, due to the double walled structure.





So, I decided to weld M10 x 1.25 bolts to thick washers and weld then to the top of the floor. I drilled the holes large enough to insert the nut, so only the washer would sit above the floor.


After welding, I primed the areas where I removed paint. With the tank removed, I decided that it would be a good time to rustproof the underside of the car with Herculiner and to sound dampen the floor with a layer of fatmat. I ended up also fatmatting the wheel wells and sides.


I also decided to add a layer of carpet to the spare tire well. I also had to punch holes in it and the existing carpet to expose the seat bolt holes.


Finally, I was ready to set the two sections of the seat in place and to bolt them in.







I damaged two of the bolts when I removed my bench seat, so I purchased two 10.9 grade bolts and used them at the front of the rails.


After tightening the final front bolts I snapped on the plastic covers and the seats were good to go:


With the new carpet in the spare tire well, the back almost looks too nice to cover up: