Let's say you have a 1965 Thunderbird. You can't legally take the V.I.N. plate off the car, slap it on another car and say "this is my 1965 Thunderbird."

You can, however, take the rear bumper off your car, replace it with another bumper, and still say "this is my 1965 Thunderbird."

Somewhere between these two extremes is the line that you can't cross. Any idea where that is?

I know that for years, people took old VW bugs and replaced the bodies with kit-car bodies. Those cars remained legally old VW bugs. Hypothetically, you could take one of those cars and replace more parts. What if you replaced the engine, trans-axle, suspension, etc.? Can you replace everything but the chassis?

  • 8
    Like the old joke: "This is the best axe I've ever owned. Only replaced the blade once and the handle twice." Commented Apr 27, 2017 at 22:04
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    I'm voting to close this question as off-topic because it is a philosophy question, not a legal one. Look up the Ship of Theseus.
    – user4657
    Commented Apr 28, 2017 at 1:45
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    Unless/until there is a specific jurisdiction provided, this question is about philosophy. In certain jurisdictions, regulatory bodies track vehicle identities through some kind of marker, and so as long as that survives, it's considered the same vehicle.
    – jimsug
    Commented Apr 28, 2017 at 2:26
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    That marker would be the VIN plate. If I take a VIN plate from a 1965 Thunderbird and slap it on a car made with all new parts, the nice policeman won't be interested in discussing philosophy with me. He will be putting me in the back of his car.
    – Jamie
    Commented May 24, 2017 at 20:46

1 Answer 1


The legal line has to do with title requirements for vehicles. There is no specific law that requires you to do anything in connection with the VIN when replacing parts, and you can swap VIN plates on vehicles, or destroy the plate – but that limits your rights with respect to the car. You need a certificate of title to operate or transfer (but not simply to own) a vehicle, per RCW 46.12.520. According to RCW 46.12.520, when applying for title, you have to include “A description of the vehicle, including make, model, vehicle identification number, type of body, and the odometer reading at the time of delivery of the vehicle”. This is trivially doable with an unmodified vehicle. Once you have that Washington certificate of title, then apparently (based on a reading of RCW 46.16a), you simply have to keep registering it. There is normally no need for a further certificate of title, unless you try to transfer it. If a new certificate of title is required, you may be in trouble for crossing a line.

In case you need to apply for title (RCW 46.12.560) on a modified vehicle, the State Patrol may (probably will) perform a VIN inspection, since there would be a discrepancy in the description of the vehicle. The full list of inspection requirements is here and this document seems most relevant, being about “homemade vehicles”, as defined in WAC 308-56A-455. The core features of a homemade vehicle is that it is:

(a) A vehicle that has been structurally modified so that it does not have the same appearance as a similar vehicle from the same manufacturer;

(b) A vehicle that has been constructed entirely from homemade parts and materials not obtained from other vehicles; or

(c) A vehicle that has been constructed by using major component parts from one or more manufactured vehicles and cannot be identified as a specific make and model.

In that case, you need notarized bills of sale or certificates of title for all of the major components – by RCW 46.80.010 this

includes at least each of the following vehicle parts: (a) Engines and short blocks; (b) frame; (c) transmission and/or transfer case; (d) cab; (e) door; (f) front or rear differential; (g) front or rear clip; (h) quarter panel; (i) truck bed or box; (j) seat; (k) hood; (l) bumper; (m) fender; and (n) airbag.

So replacing the seat may trigger the requirement for a VIN inspection by WSP. Of course there is the question of how they would know, but I'm only talking about the law.

There are various rules about the documentation that has to be provided, depending on the supplier: for example, if parts come from a private individual, the documentation requires everybody’s name, address, phone, description of parts, price, and the VIN of the original vehicle. If you can't do this, you can apply for ownership-in-doubt registration (no title) and 3 years later you can apply for title.

So, an oil change is okay, changing seats is mildly risky. While exchanging parts on a same make-and-model basis is unlikely to cause any problem, real problems could arise if there is ever a comparison between your license plate and vehicle description (if the police run your plates). If you truncate your Explorer into a Mini-Cooper, the mismatch between description and license will be noticeable, and they would have reason to think the vehicle was stolen.

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