You will pick up this quest from Dan Hager after you turn in the medical supplies. Dan will send you to the other settlement for buggy parts. There, speak to Johan who wiill task you with getting some buggy parts and take them back to Durar in Dan's settlement. There are 3 parts in total and searching around the garage should prove easy enough to find them all. After you find the last one, be ready for a small boss fight. Kill the boss (I lobbed granades at him as I'm playing through on nightmare) and the achievement is yours.