One of the studs on the rear sway bar mount is snapped off. I need your suggestions for fixing this. Thanks in advance.
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Those swaybar studs are round-head 'bolts' tack-welded inside the crossmember. The only way I found to fix this was to knock out the spot-welded head, then drill into the crossmember from the ZF side and use a real bolt & washer thru your drilled hole. Be sure to size your drilled hole for socket clearance so you can hold the bolt for tightening.
Trying to weld-repair a broken stud doesn't hold very long- possibly because weld heat anneals the result, which was too small & weak to start with. With a real bolt you can go to the next grade and size up and be much stronger. The fix is invisible to all but people who've had this happen.
Hi Jack, it looks like that fix will work for the top stud but the bottom stud is inaccessible from the ZF side because of the car's long frame rail.
Since the stud is evidently a bolt, of which the head has been welded to the body, could you dress the exposed bit of broken stud flat enough to center punch it, carefully drill through it and tap it 8mmx1.25, basically turning what was the hidden head of the bolt into a captive nut to receive a bolt from the outside?
That is exactly what I did over 20 years ago.
@larryw posted:Since the stud is evidently a bolt, of which the head has been welded to the body, could you dress the exposed bit of broken stud flat enough to center punch it, carefully drill through it and tap it 8mmx1.25, basically turning what was the hidden head of the bolt into a captive nut to receive a bolt from the outside?
Larry, that is the approach I am using now. I might be able to snake a nut onto the stud to make it stronger.
When I retrieved my broken stud-heads and found they were small, round and tack-welded in only three places, I decided I wasn't lucky enough for the other stud/bolts to be welded good enough to take drilling & tapping without breaking loose. Apparently others were lucky.
And as I said, backside-drilling of the crossmember gives one the opportunity to use a larger bolt of a stronger grade than stock. YMMV-
Grind it flush, center punch the broken stud, drill and tap it 8mm x1.25 , thread in a long (12.9 grade fully threaded) bolt until it bottoms out on the forward wall of the frame, cut the head off and dress the end of the remaining portion.
Ron
@rmccall posted:Grind it flush, center punch the broken stud, drill and tap it 8mm x1.25 , thread in a long (12.9 grade fully threaded) bolt until it bottoms out on the forward wall of the frame, cut the head off and dress the end of the remaining portion.
Ron
Did this years ago on the '72 I used to own. Worked really well.
Drilling through the broken stud, through the head and tapping it is all that you need to do.
The tack welded head will act as a captive nut and the tack welds keep it from turning. Those welds were strong enough to not spin when you snapped off the original stud. Don't hit it with an impact wrench to tighten the new bolt though.
Use plenty of oil on the tap and then on the new bolt and tighten it by hand.
I had a couple of the original studs snap off on me also and drilling and tapping what was left worked for me.
...Sure, Just drill and tap it and be done with it!
MJ
Got it fixed. I drilled and tapped the snapped off stud. I used a 60mm bolt as the starter for the new stud and cut it to length. I used JB Weld as a thread locker on the final stud, and bottomed out the stud using opposing nuts.
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Nice job Steve
so easy can it be
...Great Job! Did You use a Grade 8 Bolt? A Grade 3? (Common) will Snap-Off on the Thread Root.
When I lift the Frame, I put a Block of Wood on the Jack. I know you have a Plate Installed, but do You want that Gouged-Up?
Don't want to Offend Anybody...Just Not the way a Machinist would Do It.
MJ
I think it says 8.8 on the bolt…👍
...a Property Class 8.8 bolt or screw is a medium-strength fastener that’s roughly the same strength as an SAE J429 Grade 5 fastener.
When I build...I don't believe in 'Medium Strength'!! My Religion is 'Massive-Overkill'!! DO it Right! Or do it a Second Time!
MJ
P.S. Nice Paint Job! But, Are Those 'WELDS'?? Weld Prep!
I think the factory studs are probably 8.8 just like most fasteners on Panteras. The car came to me with damage to the stud. It was bent at almost 90 degrees, maybe from lowering the car after jacking and the stud caught on something. When I tried to straighten it the stud snapped off. Thus, the snapped stud was due to a mishap and not from driving the car.
I'm not sure why those welds are there but the car does have a thick steel plate that is impervious to the jack and no need for wood on this one. I have used a block of wood on my previous Panteras.
My other Pantera is very messed up from jacking. The sheet metal is now round. I use a jack pad for it to avoid making it worse.
A hockey puck works well too because it fits nicely in the saddle of the jack.
@davidnunn posted:A hockey puck works well too because it fits nicely in the saddle of the jack.
Such a Canadian solution!👍👍🤣
I only can use a BigMac once… So hockey puck is better!
The hockey pucks work better if you bore a 1-1/2" hole through them but you need more then one since the split easily. Maybe they saw an old girl friend sitting in the stands and want to avoid her?
You want to use a bolt marked 10.6. I personally think that the original size of the studs was too small to begin with. From experience, you do not want one of the studs on the anti-sway bars breaking on you while you are "on it".
You will likely spin the car out suddenly.
I'm always cautious of Canadian women. They are different then Americans and take pleasure in breaking off studs. 
I went to my bolt store to get a M8 10.9 bolt and the longest full thread they had was 40mm. The stud I made is 42mm. I will have to look further for a 45mm bolt.
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McMaster-Carr has 50mm studs in 10.9 and 12.9.
Wouldn't this style of stud be appropriate for this application?
They are designed for this sort of installation with two features, they bottom out against the full section shank and are cut with a tighter fitting interference thread so they will stay put and won't wobble.
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Too much unthreaded area, will not clamp thin bracket.
The weakest part is the part you threaded into… My humble opinion, a M8 grade 8.8 stud, used on, as previously mentioned, drilled out, and re-threatened original bolt hole , using the head of the left over bolt to be threaded as well should be sufficient (and the weakest link before the grade 8 bolt snaps) … and use the original rubber swaybar bushings versus the Polyurethane bushings which are not very forgiving!!
If you wanted to be really strong, you have to cut the crossmember open or make a plate sitting on top of the crossmember and weld it on.
would be a nice project…
thinking out loud:
drill a hole where the bolt supposed to be the size of the bolt head to be used, stick the bolted in the hole welded in place then make a plate with two holes where the threats only protrude and weld that plate onto the crossmember.
there are many other ways to do it and make it stronger…