welding on tranny crossmember

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While removing the tranny on my pickup truck, I cracked the metal all around the two bolt holes in the center of the crossmember, where the rear of the tranny bolts in for support.   I'd like to weld on another piece of metal to replace/restore the cracked metal.  I'm assuming that this crossmember isn't made of mild steel, but of some sort of tempered or hardened steel, otherwise it would have bent instead of cracking and breaking out, the crossmember metal seems to be somewhat brittle.  Will I be ok welding onto it a piece of thick, maybe 3/8 inch mild steel plate?  I don't have in my shop any pieces of hardened steel plate.  Also, what welding rods to use, 7018?  Thanks in advance for any advice, I'm hoping not to have to go scrounging junkyards for another crossmember.  Chuck
Reply:I've made several tranny crossmembers out of mild steel C channel and never had a problem with cracking, usually ends up being heavier than factory crossmember. Think I used 6011 or 6013, whatever was handy at the time.Rob H.
Reply:It's likely that the metal was just fatigued. Put a metal through a very large number of cycles, and it will work harden and eventually fail.You should be fine to add onto it, but I would use 7018 if you have it, 3/32" size for good heat control. Start around 90 amps.