Need advice on welding nuts to broken studs in rear suspension

[240260280z]

Hi,

The 4 bolts that hold the two differential rear hangers to the box frame cross beam broke when turning out.

I tried PB blaster and heating the remaining studs with a MAP torch, quenching and turning out with an extractor but no luck.

Today I had a welder with a 120V flux wire mig have a go but the welds would not take to the studs. They broke when turning. He also had problems welding the nuts to the studs... the washer seemed to weld ok. It seemed like the nuts may have been a poor quality steel... not sure?

Any tips on how to do this job? Does it need more heat with a 220V higher current welder?

Thanks

[JLPurcell]

If I understand your situation, I would center drill the studs using increasingly larger bits until just shy of the threads then I would chase out the threads with a tap. JLP

[Patcon]

Blue,

Which bolts are we talking about? Are we talking about the two long studs that hang down for the mustache bar or some other bolts. I can't think of any other bolts in the rear supsension that can't be removed and replaced. The two mustache bolts that hang through the floor I thought were removeable from up top, but I am not sure. I probably wouldn't try to weld them back if I didn't half to. I weld some and I would be hard pressed to trust welded bolts in the suspension.

Charles

[240260280z]

The parts are the four bolts that hold the two vertical flat steel plates that run on each side of the differential's rear cover. These bolt the plates to a box section cross beam under the rear hatch's floor. (see attachment for gory details) and photo of what it should be.

I tried drilling but no luck... could not drill into the hard steel. I think I may have hardened the bolts by heating then spraying with canned freezing spray.

[Walter Moore]

Try using a cobalt drill bit. They are harder and stronger than normal bits, and are intended for just this application. I am not sure if you have a Tractor Supply store nearby, but that is where I bought my most recent set. They are expensive however...

[Patcon]

OK :mad:, that looks like fun not! It's too bad the car is not on a rotisserie but that does make more sense now that I see it. I agree they will have to be drilled out. Which could be a real chore from under the car on your back. I would also try not drill the whole bolt at once but step up. If it gets off center some times the tap will pull out the partial thread. The bolts are probably pretty hard from the factory, but the quenching may have worked against you. I don't think you have an easy fix

Charles

[240260280z]

I am tempted to cut the whole darn box section out and replace with a re-fabricated one or graft in one from a donor car.

[Patcon]

Blue,

If your up for that just cut a section out for both bolts (maybe 2"x5" for each side), plasma cutter if you have it or die drinder, might need a 90 degree die grinder to get access. Get the bolts out the back side once it's out, then make backer plates for both areas. Put some holes in the bolt plates and around the perimeter of the hole (5/16" dia). Plug weld the backer plates into the boxes first, make holes for the suspension boltsa to pass into, then weld the plates with the bolts in against the backer plates. Weld all the joints solid and fill all the holes. Stronger than the orignal. You will have to take it easy with the heat. Wait a while between welds or cool with air or things will "oil can" on you. Even the thicker metal on our cars is not very thick and warps easily. Spent all day today fabbing up a new battery tray area, today. Slow work but stronger in the end. I think I would prefer this method over the tap and die work if the bolts won't drill. If you want, a die grinder and some 2" Roloc discs and the welds can be worked back down smooth. Will look like brand new...

Charles

[cygnusx1]

Use a dremel with a cutter or a stone in it to put a "cavity" up into the old bolt. Then you have a better chance of drilling. However it's going to be tough to not damage the threads up in there. If you could cut a deep enough slot into the end you might be able to use an impact screwdriver. The kind you twist and whack with a hammer. Shock and vibration is your friend when there is rust binding.

[Patcon]

Blue,

Did you get it fixed yet?

Charles

[240260280z]

Just buying a welding helmet tonight at harborfreight in NJ. I head back to Canada tomorrow after work 1,600km drive.

I wired a 240V outlet in my bro's garage last Sunday and I will be able to finally use a 240V welder I bought a few years ago. I hope the higher heat will help the weld stick and I hope I develop welding skills fast. I 'll update this post when finished

[JLPurcell]

Do you know anyone skilled with a gas welder. My old racing buddy, George could take the cutting tip on his gas welder and blow out broken bolts without damaging the threads. No Joke!