Well the donut thing makes me think the wheels on one side are going backwards, so check which direction the axles are set to I guess (the left side axles usually need to have inverted direction). Other than that I have no way of knowing from the limited info.

Oh, ok. The vehicle is a double decker bus, at least it will be when im finished. the moment i spawn it in and turn on the throttle thats when it does donuts

You provide far too little info in your question for me to know what might be wrong but I suggest you check if any landing gear axles are driven or not pointing straight forward, and if any prop turns the wrong way.

If you have multiple props are they all turning the same way (no counter rotating props allowed)?
Sadly most propeller planes seem to not be able to go straight on the ground even if everything is at it should (completely symmetrical build, no driven wheels on the ground, no counter rotating props etc), and that's a "feature" of the game that became even worse with the new aero in 1.3 since stabilizers and tailfins provide little to no help under 100 kph.

You don't HAVE to do anything if you re-upload but it's nice to get credit for my work.

About your vehicle, what you wrote isn't much to go on. Is it a plane? If so propeller? How many props? Does it do donuts while all wheels are on the ground or only when just two wheels are on the ground? Are the wheel axles for the landing gear Driven? Is one if them?

Real nice!

Also I have a couple of questions.
First, I wanted to make sure that I have to give you credit in order to reupload your creations.

Secondly, I'm trying to make a vehicle to post, but when I turn on the throttle, it does donuts. Know how I could fix this?