How much rust on trailing arms before replacing ?
 

Pulled the rear end and arms from my 70 C10 as an assembly. Was just going to clean and paint, Passenger side arm looks great, but driver side is spread at the middle. Used large hammer to knock out some of the rust, now there is a dime size hole on each side about 12 inch in front of spring, tops and bottoms look solid, I think its still strong enough to use, but would you replace or just run it for now and consider keeping and eye on it if it gets worse ? Thanks

Re: How much rust on trailing arms before replacing ?
 

If it were me I'd probably just weld a piece of patch steel over it the same thickness as what the arms are made from.

Re: How much rust on trailing arms before replacing ?
 

First, look at how much load the arm carries and what would happen if it were to collapse due to corrosion. :eek: Can you visualize you truck in the scrap yard?

Spread apart the metal and remove all of the rust. Naval Jelly and elbow grease. Then weld in a patch, and squeeze the metal back together, welding the sheets back together. Paint thouroughly with a rust-inhibitive paint.