1995 Plymouth Voyager Drop in gas mileage since axle replac

Thank you for your site. Since I had an axle replacement last month, my gas mileage has dropped by 65-76 miles of what I had previously gotten. Don't know if there is any connection or not, but what are the possibilities for such a big drop in gas mileage. Should I get a major tune-up?

I believe I have a good trustworthy mechanic, and I just want a second opinion. Thanks.