goes into 4 wd perfect road conditions

Hello, If you are seeing an ABS or traction control message, diagnose this first. It would likely be related to a wheel speed sensor. If not, the issue may be as simple as a failing 4WD switch, or as complicated as tracking a damaged wire. The problem here will be that the problem is intermittent, so you need it to make the error constantly before you can diagnose it. If you can set it back to 2WD using the switch, I would suspect the switch even further.