Originally Posted by wmtire

Hmm, I went and found the official DOT regulation concerning VIN numbers for trailers. Bill, it looks like you have to be a rocket scientist to figure out that check digit thing, which is explained in the regs. I'll leave that part to you. I got a headache just reading it.

Page 21 of the regs explains the digits and what they mean in a trailer VIN number. There is a sample page after that, to let everyone see what the manufacturers must submit to the DOT. Remember this is just a sample, and that each trailer manufacturer will decide the actual position and code for each of it's trailers. They just have to submit to the DOT what each code means.

Digits 4-8 tell the body type, number of axles, length, etc. Each manufactuer will decide in what digit position, it will put this info. They just have to tell the DOT what their code means.

http://www.nhtsa.dot.gov/cars/rules/...trailer002.pdf

The 10th position is the year code, which is what we are trying to find out for sure. This document at least confirms that.