This is not true as I have explained in other posts:
1. Trucks are compatible with .37 and up provided they include all necessary files and have properly written material files. Every error I have seen has been because of incomplete and missing files (including white tires), which is down to trucks not being standalone.
2. The speed does not appear to actually be different. The difference you are seeing is .37 shows only the "car speed", while .4.5 shows "wheel" and "car speed". Observe both. For me, the car speed in .37 matches the wheel speed in .4.5., with the car speed being 3 MPH slower (e.g., 13 MPH in .37, 10 MPH in .4.5.1). It's logical to conclude that.37 is inaccurate because every version post .37 are exactly the same. I've done various tests with the same trucks and tracks in 3 different versions (.37, .39.5, .4.5.1) and they all had the same results. The best example I can give is I compared the same truck using the same large jump, and always landed in the same spot in all three versions. If there was truly a 10 MPH difference the results would have been quite different. If .4.5 feels different, it's likely because of the massive framerate improvement. The only difference I found was .37 either doesn't support, or has different code for anti-lock brakes.