In a recent discussion here on seating, I believe it was @JWA who recommended ExpoVans.com and their conversion seat bases that will convert Toyota Sienna seats so they will fit in an E-Series van. As it turns out, ExpoVans has spun off its seating group and they’re now called Base-Fab. After a friendly discussion with Jer at Base-Fab, I got a pair of sliding (but not swiveling) Ford-to-Sienna bases, and a pair of new-take-outs Sienna reclining leather seats in gray to match my van’s interior. The bases shipped out UPS and arrived last week. The box got a little mangled, but the bases came through it OK.


They’re really well made, heavy-gauge steel and promise to hold the Sienna seats proudly and safely. I considered a swivel base for the passenger side, but I figured it wouldn’t get used much, not enough to justify the $300 price difference between it and a fixed, sliding one.

The seats shipped UPS Freight, on a pallet, and were supposed to arrive on the 2nd. They actually arrived in L.A. on the 29th, but with the holiday weekend, it took a while to get it sorted out, and they called on the 2nd to arrange a delivery appointment on the 3rd. Somehow the UPS guy backed that huge truck up my street and parked it in front of my house without my hearing him. I happened to look out a front window and saw it, and thought “I know what that is.” He wheeled the pallet up my driveway and dropped it behind my van, I signed for it, and set to checking it for damage. Jer wrapped it very well, first surrounding the seats, top to bottom and on the sides, with automotive carpeting and seat cushions. Then wrapped the whole thing in cardboard, then shrink-wrapped the cardboard to the pallet, then put a couple of straps on just for good measure. And it worked. The seats came through unscathed.


I lugged them into the garage and started actually reading the instructions (for a change). The seats need some modifications to go on the bases like they should, and I was concerned about what I was getting myself into. I forewarned Jer that I would be annoying him with questions, and he was happy to oblige. I wasn’t exaggerating, I’ve had several emails to him already today, and I’ve only worked on the passenger seat.

The first thing that has to happen is the plastic covers around the Toyota bases have to come off to facilitate the mods that need to be done.


This is done through a variety of screw removals, pry-and-yanks, and bend-until-you-think-it’s-going-to-break-and-then-it-pops-off. I removed one of the armrests to make it a little easier.



There are all kinds of cables and levers on these seats to operate the different functions, and because the seat (at least the passenger seat; that’s the only one I’ve worked on so far) is removable, there are 4 cables for the seat removal alone. Those all had to come out

(the seat won’t be removable without a wrench once it’s bolted into the Ford), the footrest release had to be temporarily disconnected (hopefully I can re-connect it when the time comes), the recline and footrest handles had to come off just to get the plastic covers off, and eventually, those plastic covers are off.

More stuff to remove. Since the seats use the Ford’s body-mounted seat belt and wired seat belt pretensioner, the integrated Toyota seat belt had to be hidden (I could have just cut it, but chose not to).

First it unbolts from the side, then it disappears into the hump on the top of the seat. There’s now a vestigial seatbelt inside each of my seats. Once that was out, I needed to remove the nylon strap that pulls the seat out once you’ve activated all those cables (at least, that’s how it works in a Sienna; once these seats are mounted, they ain’t goin’ nowhere, that’s why the strap is coming out).


Now the seat belt’s out, the receiver on the other side has to come off. That’s pretty simple, one bolt and it’s out. Not surprisingly, the Ford seat belt receiver won’t painlessly fit in the same hole as the Toyota’s, so we need to drill a new hole 1/2” in diameter to accommodate a piece of it. While working on my last fun project, I had occasion to buy a set of step drill bits, my new favorite tool. They can put big holes in obnoxious metal in very little time. But the one I hadn’t used yet was the one that goes up to 1/2”. Perfect. In short order, the bit was nice and sharp, and the requisite hole was drilled. Now there’s a hole for it.



Need to take off the 4 cable-activated latches that hold the seat in.


Half of those bolts will be re-used, half of them won’t. In addition to these latches, there’s a rod across the bottom of the seat frame that plays a part in the stock seat removal (in a Toyota, anyway), and it has to come out. How? By cutting it. They recommend a grinder with a cutoff wheel, or a Sawzall. I don’t have either of those.


But I do have a heavy-duty Dremel tool and some metal-cutting wheels, so let’s give that a shot. Had to cut it in two places, but it came out fairly easily, and none of the sparks set the upholstery on fire, which I view as a plus.


Now the instructions say to cut about an inch of the folded edge of the Sienna’s seat base flange in order for their conversion bases to fit. I wasn’t sure how that was going to go until I held the Base-Fab base up to the bottom of the seat, then it became obvious. But it was just about 9 pm, and that’s when my neighbors go to bed. The city says I can make noise until 10 pm, but my neighbors are nice people, and they don’t complain when I practice my guitar (loudly) all day long, so I’ll cut ‘em some slack and wait until morning.

Next I’m going to look at the stock van passenger seat and see what it will take to remove it, and to remove the seat belt pretensioner and hopefully figure out how it bolts into that hole I drilled in the Sienna seat. The stock seat bases appear to be bolted down with the same TorxPlus bolts the bench seats are. I hope that’s the case, or at least, I hope it’s the same size TorxPlus bit, because I only have one of those bits. Actually, only the front two are TP bolts. The back two are nuts that tighten down onto studs in the floor.


They apparently come from the factory with a dust cap, only one of the 4 was left on my van.

Morning came and it was a little early to start making noise, so I worked on getting the stock passenger seat out, and dealing with the seatbelt pretensioner. Two big metric nuts on the back of the stock seat base. How big? I don't know, because I don't have any metric wrenches that size. But it's pretty close to a 3/4", and that I do have, so I removed them with that, and, so far, anyway, no strippage. The front two bolts are the same T12 metric bolts as used in the bench seat bases, with the same TP55 head, so that bit paid for itself again. Getting those bolts out was easy. Getting that pretensioner wiring to disconnect, not so much. Plus it was cold, so my hands weren't exactly nimble.


But eventually I figured out that pushing the red piece back and wiggling the connector a little would separate them. Getting that connector out through the seat frame was another matter, I do wonder how they got it in there.



But eventually that came out, and I bolted the pretensioner on to the Sienna seat. There's a tab on the pretensioner that is supposed to go into a hole in the seat frame to give it a little more strength, and that 1/2" hole I had to drill was to accommodate that tab.



The main bolt used the same threaded hole the Sienna's seat belt receiver used, and the bolt and spacers supplied by Jer for the Ford unit fit perfectly. As big as that mechanism is, it's like they designed the Sienna seat to hold it. Unbelievable (and in a good way, for a change).


With that done, it was still a little early, but I wanted to get to work, so I closed the garage door and started cutting. Notched the Sienna seat frame fairly easily, front:

...and back:


and bolted the Base-Fab base to it. There are a total of 8 bolts that hold the seat to the base. The 4 on the back are re-used from the Toyota's seat release mechanisms, and Base-Fab provides the 4 bolts for the front. A little ratchet work and we're in.



Wrestled the plastic parts back in and tightened all the screws. The seat is now ready to go into the van.



But first I have to mount the bottom of the Base-Fab seat base into the van. The holes lined up with the stud bolts just fine, but, as Jer had warned, there is some insulation under the carpeting that prevents the base from bolting down safely and securely. So I slit the carpeting, cut out the insulation (padding) from under it, so a couple of cuts with a box cutter (I wore out the first blade on the passenger seat, so I had to put a new blade later when I did the driver’s side) and the base dropped right on.



Hopefully you can cut straighter than I can if you do this project yourself. Since it's under the seat base, it's likely to remain our little secret. The discerning eye will notice these pictures are a mashup of the drivers and passengers side, but the pictures from one came out better than those of the other so I just merged them for illustrative purposes.

Bolts in and tight, and it's time to put the seat on the base in the van.


This took a fair bit of finagling to get the 4 bolts to sink into the 4 correct holes at the same time so I could bolt the seat down. Then once I finally got it all bolted down, I walked around and looked at it from the driver's side, and spotted one of the washers that was supposed to be under one of the nuts. I must have dropped it in all the fun. So, take the nut off, put the washer on, and tighten it back down. With all the wrenching I've done today, one more nut removal/replacement was no big deal. Reconnect the cable to the seatbelt pretensioner, insert the headrest, and we're done.


OK, halfway done. Still have to do the driver's side.

Tough decision time. I really want to put the other seat in, but I also need to drive the van tonight, and if it takes anywhere near as long as it took to do the first one, I'll run out of time and not have a usable driver's seat, and that would be bad. So, grudgingly, I decided not to try to finish it today. But I still had some time to work on things, so I opted to start in on the driver's seat. The modifications go a whole lot faster if you've done them before. So, handles off, screws out, plastic parts off, cables detached and removed, seat release mechanisms removed, seatbelt buried in the seat, center rod cut out, flange notches cut, 1/2" hole drilled, top half of base attached, all in about an hour. Used up every one of my Dremel cutting wheels, but got the job done, and no upholstery fires started. All that's left is to put the seatbelt pretensioner on, put the plastic parts back on, and mount the seat in the van. But I can't put the plastic parts on until the pretensioner is installed, and I can't install that until I uninstall it from the stock seat and take it out. And I can't do that if I'm going to drive it tonight and tomorrow morning. So the rest will have to wait until tomorrow afternoon. That will also give me time to think about what to do with this power outlet/USB charger I put on the side of the driver's seat some time ago.

I expect I'll figure out a way to mount it on the new seat bases, it's looking like this project ain't gonna be done until Sunday afternoon.

And as it turned out, it rained all Saturday afternoon, thereby complicating what I needed to drive the van for (an outdoor music gig), and precluding any work in the driveway by the time I got home. Sunday came and lived up to its name, it was sunny and warm by January standards, so I got back to work. First, let’s get that pretensioner off. One look at the existing seat and I’m convinced I’m doing the right thing with this project.


One bolt, no sweat, let’s just disconnect the cable, huh? There are two connectors on the cable, not one. But only one is connected.


Well that’s not going to fit between the two pieces of metal on the stock seat frame. How are we going to get that out? I don’t know, but it’ll probably be easier with the seat out of the van so I don’t have to do it upside down.

Two nuts and two familiar TorxPlus bolts and the seat will be out, right? Not quite. I learned today that someone, likely a previous owner or passenger of the previous owner, dropped a lemon-lime (judging by the smell of it) lollipop on the left-most nut on the rear of the seat base. And it’s been there for a while, and that’s going to add a little more time to the project. How did the car dealer not see this when they detailed it when I bought the van last year? Oh well, time to deal with it.


This made removing the nut just plain sticky, and my 3/4” wrench did not want to play nice with this nut. I don’t have a metric wrench that big (19mm, by my estimation maybe 17, I’m writing this after the fact and I don’t exactly recall), but I didn’t want to buy a whole set of metric wrenches or metric sockets just to get this nut off. But lacking any better ideas, I went down to Harbor Freight (I took my wife’s car and parked in back to avoid having anyone I knew see me going into Harbor Freight), held my nose, and bought some metric wrenches and deep-well sockets, though I didn’t get the color-coded ones, those just reeked of cheapness (even moreso than the ones I bought). Back home and coaxed the nut off, then took the other nut off, and got it all sticky, too (should’ve done the clean one first, but, too late now).

Took my ratchet wrench, new socket, new combo wrench, and both nuts, and washed them with hot water and dishwashing soap. Clean at last. Soaked a paper towel in some more of that and cleaned off the bolt studs in the van floor. Dried everything carefully.

With the seat now out an on its side in the driveway, I extracted the cable from its many hold-down fasteners

and looked at how to get it between the seat frame and the glide rails. No apparent way. It went in there somehow, though, and I doubt they shoved the wire through and THEN put the connectors on, so how do we...aha. There’s a bolt inside the glide rail track,

and another one on the back of the bottom of the seat frame. Will those come out and widen the space where the wire goes through? Yes! Free at last.

It was a lot easier to shove that connector and cable under the seat cushion of the Sienna seat than to extricate it from the Ford seat. Bolt it down, reattach the plastic sides, and, very important, reattach the two elastic loops like this one that hold the end of the carpet on the back of the seat, and we’re ready to go into the van.


Once the base is installed, that is. That went the same as the passenger side, a little less insulation removal, but just as much carpet cutting, so I’ll spare you the repetition.

Now a word about my experience in putting the passenger seat in. There’s the base that bolts to the van floor, and there’s the upper part with the glides on it that bolts onto the seat, and that part bolts onto the base. It bolts on to the base using four bolts which protrude through the bottom of the glide tracks. The good news is, when they’re in place the way they’re supposed to be, you don’t need to hold a wrench on the bolt heads to tighten the nuts once you set the seat down on the base. The bad news is, if you don’t set that top part down exactly on the four holes on the base (and if the glides moved at all while you were installing the base, which they will, they won’t be aligned for the holes in the base when the time comes; don’t ask me how I know), at least one (and probably more) of those bolts are going to push up into the track and you’re going to have to fish them out, or push down on the seat adjuster lever and move one or more of the tracks to get to the bolt and push it back into its hole again. And if you don’t get it in the hole the second time, you get to repeat this process. I didn’t want to go through that again on the drivers seat, so I thought “What can I do to hold those bolts in their holes if I miss the mark when trying to set this (heavy) seat down in the right place? I concluded that folding up some narrow strips of cardboard and shoving them into the glide track above the bolt head would hold the bolts in place and I could pull out the cardboard once I got all the nuts started. This actually worked really well, and I got the four bolts seated in very little time. The worst thing that happened was some of the grease in the glide tracks got on the cardboard, but I think there will be enough left in there to lubricate them for quite some time.


Thanks to the cardboard trick, the driver’s seat went in fairly quickly, and I got all 4 nuts started. Unfortunately, there wasn’t enough room to slip a ratchet and even a small socket onto these nuts, so I had to tighten all 4 of them with a 13mm combo wrench, which took a while. But eventually, it was done. Connect the pretensioner cable, and, hmm, WE’RE DONE!!!


Now let’s sit in this bad boy and see if I really have more legroom. I took Jer’s word for it when he said the bases would help the seat go farther back than the stock seat (my reason for doing this project in the first place, so I've been operating on faith the entire time and hoping for good karma), and that it would probably be enough. But was it? YES!!! I’ve got LEGROOM!


I don’t get that very often in any motor vehicle, so forgive my exuberance. But I have legroom in my van now. No more knee-tormenting funny angles to hit the gas and brakes. The seat sits up a little higher, too, which I like, almost as much as I like having to actually extend my leg to step on the gas. A little vacuuming to get all the little leaves and grass and everything else that stuck to my feet in the rain yesterday, not to mention the powdery yellow mess that the decomposing stock seat upholstery was leaving on the floor, and it looked much better. One last touch, figure out what to do with that power outlet/USB charger, I mounted it under the outer plastic side of the seat, where it won’t hit or be hit by anything, and now it’s really done.


I thought these were all the tools I used, actually not all of those sockets, and in truth, there were a few wrenches I’d left in the van that I found after I shot the picture and had put these tools away. But this is most of them, including the folded-up cardboard.


When you’re done with this project, you have a lot of removed Toyota parts to get rid of, this is most of them, there are some more cables, and one more seat release, but this is most of it. If you have a 2018 Sienna and want some spare seat parts, let me know, otherwise, these are trashward bound.


I’ve had a chance to drive a bit with the new seats, and it’s a night-and-day difference. Well worth the effort and expense. That new Hellwig rear sway bar sure makes it more fun, too.

 

That's a hell of a project.

How are those seats? Do they fit grown-a$$ men or are the like most seats from Japan and fit, um "average" men but torture those that shop in the "tall" section.

When I drive my van, it's for hours at a time.

 

I'm 6'2" and 250 lbs. My a$$ is as grown as most, probably a bit more. They feel snug to sit in compared to the stock seats, but they're comfortable. I suspect that if I'm not careful and don't make an effort to stand up out of the seat instead of sliding off, the left bolster on the seat will wear down more than the right, But on the road, it's comfy. My drive home yesterday was about 2 hours, and I enjoyed it. A 2-hour drive on the old seats would torture my right knee because of the weird angle I had to keep my leg at to operate the pedals. Those days are over for me.,

 

Fantastic write up!

 

oh HELL YES 'twas! As a side note the parent company of Base Fab is lead by a supremely talented genius---I first became aware of his work and designs through another forum which deals mostly with van conversions such as ExpoVans builds.

A few comments for those thinking of this project for themselves:

1 Fasteners holding stock E-Series seat bases to the body are a Torx Plus T55 bolt and 18MM nuts.
2. Its advisable disconnecting the negative battery terminal about 15 minutes prior to separating the Ford pre-tensioner connectors---this allows any stored electrical energy in the SRS to dissipate. Not doing this runs a very small but real chance of the SRS being triggered, air bags deployed. This is not only costly and messy its potentially dangerous if your body isn't positioned properly.

So now that the disclamers are out of the way........

You did a great job documenting and detailing your process GiffenF, massive kudos for being so thorough in that alone. (Reps sent BTW.) I'm hard pressed to even think had you had more tools you'd have better results---diligence and creative thinking can over come a lot of issues that crop up in the middle of a project. You did exceedingly well in that.

Now for a few questions as I'm now strongly considering adding the drivers seat only---I rarely travel with a passenger so that seat would remain stock. So the biggest question is what was the landed cost of the seats and bases? I have access to several commercial docks which might be helpful but doesn't seem to be absolutely necessary. Another question is once a Sienna seat is installed and adjusted for the occupant all the cable releases etc wouldn't be activated correct? I see those being slightly problematic over time if they were frequently operated.

And a third question relates to seating position relative to height of the seat cushion relative to the stock Ford seats---higher, lower, adjustable or fixed? (I'm 5' 6" but do ride with the stock seat at its furthest back position.) Along with the tilt wheel this is a very comfortable position for me.

Once again great project write-up and looking forward to your replies/thoughts.

BTW running Hellwig bars even if its just adding the rear is a great addition to the E-Series. On my '05 E350 extended body raised roof van I've installed both front and rear Hellwig bars spec'd for a short wheel base motorhome (p/n 7008 front & 7085 rear). Along with Bilstein shocks spec'd for the same SWB MH I've got a very nice ride that feels quite well connected to the roadway.

 

 

As I begin digging into this it (naturally) seems there are different versions of Sienna seats, those like you're showing us GiffenF are the very higher end of the option list. I don't need or really want all the reclining features etc however if that's the only way to get a better seat overall that'd be fine. I'll have to first acquaint myself with which Sienna seats would work for me.

An email from Jer says they don't separate their pairs of front seats, buying just one base doesn't seem to be a problem though. Doing a bit of internet searching for Sienna seats I can find more than a few locally for well under $300 each but I'm fairly certain they're not the "better" versions. Its possible I'll have to keep hunting for a nice GC take out seat, driver's side only. Or I might have to buy the front pair and put the passenger side immediately up for sale.

If nothing else I'm interested to see how far I can go with this and not end up with two high end Sienna seats.

 

Great job on the write up!

 

When I put Kia Sedona seats in mine about a year ago, I found it easier to remove the terminals from the plastic connector to remove the pretensioner wires. Changing the seats were the best thing I've done to my van. I'm also 6'2ish and 250ish and found the stock seat extremely uncomfortable. I also moved my cargo divider back about 5" allowing for the seat to further back then I need it to.
I made my own adapter plates to mount to the stock bases and have about $60 in my swap since I bought my seats on a half off day at the junkyard.
https://www.ford-trucks.com/forums/1...nger-seat.html

 

Having been aware of the vendor GiffenF bought his seats and bases for a few years I'd go that route myself too if only for the massive support, relatively ease of installation and a high quality end result as part of the sale.

Sadly I don't have regular access to much in the way of metal fabrication so using Base-Fab's bases I'd save myself a few days and who knows how many miles driving to DIY any sort of reliable and safe adapter base.