New crazy idea: Unibody chassis swap! Dropping classic body shell on top of a modern car unibody and running gear

Submitted by Dan on Mon, 10/29/2018 - 16:13

Update: I actually did this! Keep reading below to read all about how I put a miata chassis inside of a VW body shell, but here is the video showing my whole build from start to finish:


So I came across this guy who's putting a VW Karmann Ghia body on top of a Prius chassis that he chopped the body off of but all the running gear still intact. 

He's still finishing it, but he successfully did the same thing with a '41 Chevy pickup. He got it running and driving and now he enjoys a classic pickup with 40 mpg, power steering, power brakes, silky smooth suspension, you get the idea. 

Yes there's a Prius under that. 

He welded the frame of the truck onto and on top of the bare Prius chassis, and the truck body was so large that it just engulfed the Prius and you cannot see it at all. For the controls, he extended the brake pedal and steering shaft and routed them into the cab of the truck. The throttle is fly-by-wire so all he had to do was bolt it to the cab. For the instrument cluster, he cut out the truck's gauges and you just have to peer through the hole in the cab to see the Prius's dash (lol). 

With the Karman Ghiaa, it is a lot more complicated. He is removing the bottom few inches of the Ghia body, including lower thresholds for the doors (rocker panels?), to make it fit the width of the Prius's inner rocker panels sections - but it will also help to keep the Ghia body low enough for the right stance. Then he'll need to weld it all up including an outer skin to make new rocker panels. He can't make the Prius "sled" any narrower without removing the unibody structure holding it together. But the benefits are that he'll be able to use the dash of the Prius inside the cabin of the VW, giving him access to the controls for AC, heat, cruise control, the gauges, infotainment, etc. 

I asked him, "which build was easier and which do you recommend others try?" He said, "Knowing what I know now, the truck is an easier build. There are a few cars out there I’d like to do, the 1965 Corvair is only 2” difference on a gen 2 Prius. What I have learned is to leave as much of the Prius systems in place as possible. I moved to much around on the truck and wished I would’ve left it all in the original places. If you do a truck you need to move the rear speed sensors to the front hubs so the computer sees four wheels turning. Other than that leave everything else alone. Measure everything, wheelbase, width, distance from front wheel to windshield, strut height, strut width. As you can see there’s a lot of Prius you can cut away. Finally, weight and aerodynamics matter. My truck is 300 pounds over weight and the drag is a LOT more than a Prius. The Ghia with come in under weight by as much as 500 pounds. The the drag with be about 3.5, not as slippery as a Prius, but pretty decent."

With my interest fully perked, I started researching this and looking for more examples of this strange idea. And I found some more! Here's a Avanti's (fiberglass) body on a Nissan Leaf: 

avanti body shell on to of electric Nissan Leaf

Loyd, the builder, said, "Basically I cut the rocker panels back about 5" each side (as the Avanti was narrower than the Leaf). I welded 3/8" plate on to the remaining rocker panels. then I welded a 2X4 box "frame" under the new rocker plate. A 3/8" plate was welded between the rear shocks. A torque bar was attached between the front shocks. The Avanti body has a built-in metal roll bar which I welded to the new box frame and new rocker panels. The new "framed unibody" is very solid and flex-free."

And below is a VW bug's body shell being lowered onto a 2001 Porsche Boxster. More pics: https://www.engineswapdepot.com/?p=21935

VW bug's body shell being lowered onto a 2001 Porsche Boxter frame chassis drivetrain

That last one is my favorite. I've always wanted a Beetle. 

Here's my plan: VW Super Beetle body shell on top of a Toyota Yaris. Why Yaris? The wheelbase is close enough, it's narrow enough which is hard to find (the Boxster is wider, too wide IMO), they're easy to find and cheap, they're made by Toyota (a manufacturer I have a lot of respect for because of their reliability and low cost of maintenance), and it's a simple little car with all its running gear well contained (electric steering, fly-by-wire throttle, no hybrid batteries, etc). Most helpful to me though is that my wife has one and I can take measurements off her car. I also like to drive it around and, while the seats aren't my favorite, it's a very quick little car and fun to drive. Its like a go cart. 

The goal is to have a modern, daily-driveable, safe, maintanance-free car with the appearance of a classic VW bug. It must have air conditioning, heat, cruise control. stereo, brakes, suspension, instrument cluster and gauges, ABS, traction control, gas tank, etc. all from the Toyota. It's not about "high performance," otherwise I replace the aircooled engine with a bigger one, rather it is about the good performance of a convenient, reliable, comfortable, and safe modern car with the hansom looks and endearing charm of a classic car. A daily-driver VW Bug.

Here's a 2000 Yaris's engine bay:

2000 Yaris engine bay

Think it will fit?

Clearly the inner-fenders will need to be cut up a little but I think it will fit. The limiting factor will be the location of the strut towers. Will they clear?? I'm still not totally sure about that. But I know that a guy successfully put a Karmann Ghia body on top of a Prius, both of which are wider than a Bug and Yaris, respectively. And multiple people have put Bug bodies on top of Boxters, which are much wider than a Yaris in the rear, but are rear engine vehicles like the Bug. 

Here's some measurements:

  Karmann Ghia Beetle Super Beetle 2000 Yaris 2010 Yaris 2000 Prius 2007 prius scion xb rav4 Boxster
wheelbase 94.5 94.5 95.3 93.3 98.8 100.4 106.3 98.4 104.7 95.2
length 163 158.6 161.8 142 153.5 170 175 155.3 167 171
width 64 61 62.4 65.4 66.7 67 67.9 66.5 68 70
height 52 59 59 59 59.4 58 58 64.6 67 51
front track 52 51.6 54.3 57 58 58 59.3 57.3 61.4 57.5
rear track 53 53.3 53.3 56 58 58.3 59.3 56.3 61.4 60
tire diameter 25 25 25 23.7 23.7 23 24.5 23.7 28.5 25
horsepower 50 65 65 68 69 108 110 103 158 217
weight 1830 1780 1874 1884 2094 2900 2890 2400 3000 2800

I'm still researching this.....

Questions:

  • How am I going to attach a Bug's body shell to the chopped up Yaris chassis?
  • Will it have the right stance?
  • Will the Beetle's running boards be wide enough to hide the Yaris's unibody subframe at the rocker panels? 
  • How does this get titled and tagged? In most states, I think the VIN on the body is used. I know from experience that the Kansas Highway Patrol, when inspecting out-of-state vehicles when a new owner needs a title, they just look at the VIN under the windshield, quickly check that its not stollen, and then collect your money. No inspection. That's it. But what if the VIN on the dash of the Yaris is seen? Maybe I should call them first... 
  • I'm wondering how the VW body shell will hold up without a real frame. VW did not design it to be a unibody car. Technology has advanced quite a bit and today's cars use special steel and structure techniques to get away without a frame underneath the body. The door pillars, roof, and even the windshield are all major parts of the unibody. But on the other hand, the guy that is building the Prius conversions showed a video of him driving the Prius "sled" around a parking lot and it held. 
  • The Yaris's wheelbase is actually 2" too short. Is that too much? Lengthening it might be out of the question. What about welding the rear half of the Bug chassis, sans engine and stuff, to the front half of the Yaris chassis? 
  • The width of the Yaris dash is too wide and will need to be shortened up. What will be in the way? Obviously the air vents, but what about any wiring and computer things? 
  • Should I consider a Miata? People are cutting them up to build "ghetto karts" so their unibody should be well understood by now. 
  • Is this safe??

What about...

  • the airbags?
  • the windshield wipers?
  • the windshield fluid?
  • the spare tire?
  • the anti theft system?
  • the gas tank and it's filler neck?
  • the keys? I guess I would need two keys, one for the ignition and one to unlock the doors. 
  • air flow to the radiator? 
  • air flow to the AC/heat blower motor?
  • access to the engine for maintenance and repairs? 

....update: Actually I think a Scion xD would be a even better choise than the Yaris. Bigger engine, bigger wheels, and - most importantly - the EXACT SAME WHEELEBASE AS THE SUPER BEETLE. And while the older, smaller Yaris looked good on paper, that last one was made in 2004 (it would be so old, whats the point?) and it didn't occure to me that they weren't really selling them in America (or, at least I can't find any used ones) until the 2nd generation, which is too long.

I don't know if these drawing I found on the internet or accurate but when I overlapped the Scion xD over the Super Beetle in photoshop, the results where very promising. But It looks clear that at the very least the radiator would need to be moved, possibly to the rear. Thankfully it is a very small radiator. That would be more of a pain for the AC condensor though... 

The dimensions:

FIELD1 Beetle Super Beetle '99-'04 Yaris '05 - '13 Yaris Scion xD Miata NA Miata NB
wheelbase 94.5 95.3 93.3 98.8 96.9 89.4 91.7
length 158.6 161.8 142 153.5 155 155 157
width 61 62.4 65.4 66.7 68 66 68
height 59 59 59 59.4 59 48 49
front track 51.6 54.3 57 58 58.6 55.5 55.7
rear track 53.3 53.3 56 58 59 56.2 56.7
tire diameter 25 25 23.7 23.7 25 24.5 24.5
horsepower 65 65 68 69 128 140 166
weight 1780 1874 1884 2094 2625 2400 2500

So a Scion xD is slighly more preferable than a '05-'13 Yaris because it has a bigger engine and the perfect wheelbase. But they're harder to find. What about a Honda Fit? Wheelbase is 99" so a little to long but it can be shortened up. It's an option. What about a Toyota Matrix? A little wider and longer. How about the Miata NB (1998-2005)? They're aging, they're the right width though but the wrong wheelbase (too short!). But their racing performance would make them more attractive. It's a shorter car, would be easier to fit the engine and radiator, and get a better looking stance for the Beetle. Worth a look! New later model Miata NC shouldn't be ruled out either just because its an inch wider on either side. It's sill narrower than the Boxster which was shown to fit under a Beetle body, though IMO the rear wheels were too wide. 

This might just work...

Oh Snap!

Aircooled VWs on Miata chassis are kind of a thing.

Hmmm. an aged Miata might be getting away from my main goal of adding modern reliability, safety, and convenience to a classic car body. And they're not that cheap. Oh, and they're rear wheel drive, so lengthening it would mean also lenthening the driveshaft. A guy building a Miata + Volva P1800 (and he still is, after 5 years!) had this to say: "If I ever do another chassis swap, I will find a donor with a proper wheelbase match. That was a bit of work."

So I think the Scion xD is still in the lead for the best car (for me) to drop a Bug body shell on top of. However, they were not very popular and did not sell well, so there's not to many of them around. BUT! I just found one on copart.com - a salvaged car auction website - that had a minor collisoin in the rear (good!), has less than 100,000 miles, and doesn't have any title at all. I think that means that no one will buy it because they can't tag and title it. So, I could get it for like $500. What do I got to lose? If I doesn't work out, I can use the parts on my Wife's 2013 Yaris which is the same vehicle almost, just a different body and slighly smaller engine. Decision making time....


[update]

I had an epiphany last night. 

Instead of finding a car with the perfect wheelbase, why not weld the back of the Beetle's chassis onto the front of the Toyota's unibody? Overlap them, cut the unibody to the correct width, use the Beetle chassis's perimeter body mounts and beef them up to replace what was cut off the unibody, add support braces as needed. Transfer the rear hubs from the Toyota to the rear suspension of the Beetle so that the wheel speed sensors are preserved. 

This is what Hoopie did with his Prius + classic pickup:

classic truck frame welded to Prius unibody and drivetrain

And he made it look easy. That project is done and a driving success. And he personally told me that the Truck was a lot easier project than his current Prius + Karmann Ghia project he's still working on. 

With this method, any car or truck body could be used. How about a Ford Falcon + Toyota Matrix? Falcons are nearly as numerous as Beetles. 

Nope. Falcon is too narrow, hood is too long and low, driver seat all wrong, falcon engine bay has no room for radiator, etc. 

How about a truck then? Chevy C10 + Toyota Matrix:

Hmm, much better. Surely the controls would need to be extended and the wheels would need spacers, but this would be a fairly simple operations compared to the others. There's more than enough room for the radiator, strut supports, etc. The truck could be lowered in the rear to match the height of the donor chassis and correct the stance. I like it! A short bed would be all the sweeter, but since the frame is already getting chopped it would be pretty easy to make a long bed into a short bed if its a step side. 

So it's between a Beetle and a Yaris or Scion xD, and a truck and a... Matrix? Prius? Rav4? Highlander?


[update 2]

A Yaris will not fit under a Beetle body. The Yaris's strut towers are about 33-34" off the ground and spread out about 50". And from the best I can tell (looking a photos and blueprints, not actually measuring anything) a Beetle simply doesn't have enough space above the wheels for it to fit. I know that the Bug's windshield is 44" wide. A Karmann Ghia might have enough room, but not a Bug. 

But a Miata fits. Both the Miata NA and NB.

 

So do I want a #MiataBug? Would it have a soul "that would grow to become the stealth pre-cum of bro culture, with pickup artists and aspiring date rapists messing with headlight motors to make the cars wink at community college girls." Seriously though, Miatas don't have the daily-driver potential, reliability and safety of the Toyota compact cars I originally had in mind. Hmm....


[Update 3]

I found my victim! It's a '73 Super Beetle. The body is straight and mostly rust free, the exterior looks good, and the windows and doors and stuff all work. It actually is running and driveable but barely. The thing is a death trap and every time I drive it, it feels like I'm cheating death. It smells like gas, won't start again after the engine is warmed up, the front brakes are malfunctioning, the gear box is nearly impossible to shift into 2nd, and the engine has NO power. I can't wait to change all of that!

Super Beetle chassis swap victim

And as I suspected, a Yaris will not fit under the bug body because the strut towers are about 4" too tall to fit under the front fenders and 10" too wide to fit between the front quarter panels. Right now I'm wondering if I can install lowering springs or coilovers to get a few inches more clearance, but the whole idea of hiding a complete & well contained modern drivetrain under the beetle body is getting harder to imagine. A miata would have a lot less trouble with clearances up front, but it would come with a whole set of other obsticles such as the fact that its wheelbase is too short and it is rear wheel drive and therefor the driveshaft needs lengthened. Another option is to make it a Baja Bug! A simple engine swap is still an option. What's NOT an option is keeping the bug the way it is. The thing is a death trap! 

I briefly looked up EV conversion kits. $17k! That's for people who have money...

The madness continues here: http://dannix.net/node/119