No problems with any locomotive of IR. All r good.
The main thing is not the locomotive alone...main is the coaches that form the rake which is pulled by the locomotive. If you form a rake with all 1997, 1998 made coaches which r nearing retirement and you give a WAP7 or other high power locomotive and if u want to pull that rake like a Rajdhani exp speed of say 120 -130 kmph, an Accident is waiting to occur then. You can give a WAP7 to such train but speed has to be limited then. Yes WAP7 has many features i am not going yo that , and i am also not a locomotive expert. So, as a layman,...
more... According to me Coaches have to be fit. It is the coaches that is pulled by the engine and coaches not good, then give whatever high power engines no use. And also the Railway tracks have also to be that good. All together matter.