hey on my car… there is a hole on the front of the frame rails… and i was woundering… if i gotta get new rails?. or do i jus patch it… or wt should i do with it… and how much its gonna cost… for each?.. thanks for helping…
on the subframe? or on the unibody rails? casue on the body i dont know how well it can be fixed. ne else know this?
you can get them welded with new metal (patch) can cost anywhere between 100-400+ depending on how bad it is, but every situation is different, pics would help
mine was super bad i had a hole about 6 niches long in it and my front drivers side strut tower where it is conected to the frame rail was nearly non-exsistant it was bad cost me $1000 tow included no motor in at the time and they fixed a few more spots
return your car to the forest.
anything can be saved… but if you have the option to look elsewhere and save you some grief, go for it. Sadly, that’s what Spilner was trying to say in a less polite way. 
I have fixed my frame rails once and didn’t do an appropriate job. I made sleeves and welded them overtop of the existing frame. This reduced flex in the body but it wasn’t the same.
Currently I have replacement rails from Avery and will be welding them into place soon. I suggest you replace the metal and don’t make sleeves.
Nissan actually sells replacement frame rail sections…
and their are part #s for each piece… as to what Nissan will charge you for the piece’s of Frame Rail you need, I have no idea…
in most cases when the frame rail is rotton, so is the floor pain and everything else. so once you actually cut away all the bad frame section and get all the inner rust out, you realize their is NOTHING left to weld too. and you actually (in some cases) have to re-do sections of the floor pain and shit so that you will have new/good material now to weld to frame rails too (cause remember, its a uni-body).
If the inner parts of the rail are real bad… you will need to remove the engine in order to have it fixed properly. and reason is simple, there is no room to get in there to cut away old material, fit in new material and then weld.
Depending on how bad your damage is… get ready to pay between $250.00 - $1500.00. (that is, if you cannot do it yourself)
which is why a few people above pointed out you may want to just look for a new chassis