Travelled last month from Karachi to Islamabad on following route.
Karachi till Lodhran by N5 (National highway is in good condition through out)
Lodhran till Khanewal by E5 (Condition is excellent, Just like motorway)
Khanewal till Gojra by Khanewal - Kabirwala - Shorkot - Jhangh - Gojra (road Condition is Okayish, single road with lots of traffic like chingchi, buses, scooters)
Gojra till Islamabad by motorway