It looks like the amount of XP to unlock something in the garage is wrong or I don't understand it.
It says that I need rank 8 and 3630 XP left:
But I need only 330 XP to reach level 8:
Try to do task/contract and see if it unlock the upgrade, if it does the value is not updated properly.
Had that in 4 all the time without thinking too much over it.
@Raphael Yes. It unlocked. The amount of XP is correct in the player profile. It's wrong only in the garage. It still unlocks with rank 8 but the number "3630" is just wrong.