Drive Shaft Threads Shredded Possible To Still Use It?

Question

Just went ahead to change my transverse link/control arm, the drive shaft was stuck assuming from rust and I couldn't get it free, hammered it with the nut on and nothing, then with the nut off and it came loose. Such a stupid mistake as I damaged the threads on the driveshaft, as well as the nut. Now the car is undrivable of course.

The threads are damaged only on the first few about 7mm of the driveshaft start point, far away from the cotter pin hole (thankfully).

The nut is also toast though. From the damaged start threads whereby just putting a new nut on will damage it as well and probably further up the shaft itself.

I have removed the driveshaft off several times prior and never had the nut itself loose/damaged cotter pin.

I am thinking of grinding the broken threads down up until the good section and thereby just put a new nut on? However I am just wondering how can I make it so that the new nut doesn't get damaged/stripped as well, does there need to be a sort of cut "entry" groove?

I don't fancy changing the whole driveshaft end.

Answer 1

I don't think I'd advise anyone to do as you've done to reuse the axle shaft.

That said, people are going to do what they are going to do. In that instance, cut down the threads to get past the damaged threads. If you can do this and still have threads above the hole for the cotter pin, then there probably wouldn't be an issue. That would be a good scenario. The better scenario would be if there are still threads above the castle portion of the nut. Mind you, it is the base part of the nut which actually holding. The castle portion is just there to keep it from spinning when the cotter pin is through it.

To get it to go onto the non-damaged threads after clean up, you need to put a chamfer completely around the top of the non-damaged threads. The chamfer will allow the new threads on the castle nut to thread easily. If you don't, it can still thread, but it'll be a huge PITB to get it done and cross threading would be something which could easily happen.

You may be surprised that the damage goes further down than you'd think. If so, you might need to either get a die to clean up the threads or you could possibly carefully use a small triangle file to clean them up. Either way, it's still going to be some work.