I am an automotive service writer. I deal with third party warranties daily. The Maxcare warranty is one of the best. That warranty is actually handled by The Warranty Group.

https://www.thewarrantygroup.com/consumers

I've never dealt with or heard of Carchex, so I can't comment specifically about them.

I just dealt with a mechanical warranty through Geico for the first time. I never even knew they had a mechanical warranty product. I called in a list of problems. They sent an inspector out and blew off everything except one repair. I'd not recommend them.

Did you check with Chrysler to see if they'd sell you a warranty?