If you sign a personal guarantee for a corporate indebtedness, you are personally liable. The fact you didn't give your social security number in completely irrelevant.
If the trucks are unregistered, they are governed under Uniform Commercial Code Article 9. If the bank repossessed them without giving you proper notice, then your guarantee is discharged even though the bank may have re-sold the collateral for less than the amount of the debt.
Under various laws, the bank has an obligation to you as a surety. If they violate that obligation, you might be released as a surety even though the underlying debt has not been paid (this is commonly called a "suretyship defense").
You need to figure out what the facts actually are and consult a local lawyer.
I am admitted to practice in Connecticut and limit my responses to CT law.
yes, you signed and agreed to pay for the trucks.
there is a lot of money at stake, and the trucks are driving around possibly getting ruined or causing injury to pedestrian(s) and so forth. you would therefore be wise to consult with an attorney sooner rather than later.
also the SSN is a non-starter defense.
This is general legal information, not intended to apply to your specific case. And I may not be licensed to practice in your particular state. Under Federal Law, I am a debt relief agent.
You signed a personal guarantee, as did your partner. You have liability. Whether your bank was given your SS# does not have any impact on that. The bank can choose to go after you, your partner, or both,unless there is something in the contrary in the guarantee. If for some reason the bank does not go after your partner for any amounts it is still owed and just goes after you, you can pull your ex-partner into the proceeding to be sure he pays his fair share.