My dad needs a new car his credit scores are in the mid 500's my mom's scores are in the high 600's. The problem is she dosen't have a license, but dad does, can mom be the main signer and dad the co?

Also they are retired, they live on a pension and social security how will this affect them as well?

the loan amount is about 18k

Yes, although your mother may be required to provide some form of State issued ID. Most states have these I believe instead of DL's.

If their income is sufficient to support the payment and if necessary they can provide proof of stated income, so the pension and social security benefits if sufficient should be no problem.