I'm not sure I understand your quest, so I am going to ask you some questions to clarify things.
my grandmother is goign to be renting me and
ECV.
Do you know where she is renting it from?
Most of the companies don't rent
ECVs for people under 18 to use (I don't know what your age is, but just thought I would mention that if you will be younger than 18).
We are getting it from the hotel,
This is where I am lost.
Do you mean the ECv is being delivered to your hotel?
All of the off-site rental companies will deliver to your hotel. I'm not sure what you mean by "getting it from the hotel."
Did someone at Disney help her to make the reservation for the ECV?
now when we go to unverisal will they let me take the wheelchair in my van so i have it at unversial?
I am lost here too.
Do you mean wheelchair or ECV?
If you are talking about a wheelchair that the resorts sometimes loan to guests, they will not let you take that to Universal because the wheelchair is owned by WDW and is not allowed to go off of Disney property.
If you have rented an ECV from an off-site company, you would be allowed to take it with you in your van for a day at Universal. You just have to make sure that the one that was rented for you can be transported in a van. Some can only be transported in a bus or van that is equipped with a lift or ramp. Others are designed to be taken apart and put into a car trunk of the back of a van.
If someone at Disney made the reservation for the ECV and you will be leaving the WDW resort to stay at one of the Universal resorts, you need to make sure theat the ECV was rented for your entire stay and not just for the WDW portion of the trip.
Please let me know if this answered your question. If I really didn't understand at all, pleas help me out with a bit more information and I'll try to answer.