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Tourquing down LCA bolts with an impact driver

andrew4fins

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Ok, have done searches and my Google fu is weak. Doing my LCAs and I know specs are 190ft/lbs or 103 ft/lbs + 135 degrees. My question is can I use the impact to torque them down. My line of thinking is torque to 103 with wrench then mark the bolt so I’d know when I hit 135 degrees and use impact from there till hit the mark. Have a Milwaukee M18 Fuel 1/2 impact. The big boy. Have breaker bars etc. just trying to avoid that route and use the impact if possible. Have never had to torque anything to these specs so figured I’d best ask opinions. Thoughts? Dangers?
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Ok, have done searches and my Google fu is weak. Doing my LCAs and I know specs are 190ft/lbs or 103 ft/lbs + 135 degrees. My question is can I use the impact to torque them down. My line of thinking is torque to 103 with wrench then mark the bolt so I’d know when I hit 135 degrees and use impact from there till hit the mark. Have a Milwaukee M18 Fuel 1/2 impact. The big boy. Have breaker bars etc. just trying to avoid that route and use the impact if possible. Have never had to torque anything to these specs so figured I’d best ask opinions. Thoughts? Dangers?
Personally, I wouldn't rely on any impact gun when putting final torque on important hardware. They are nice to use to avoid having to run longer fine threaded bolts down by hand, but nothing beats a torque wrench to bring them the final distance.
 

TX_Ovrlnd

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It is never a good idea to final torque with an impact that's why your searches returned very little, no experienced mechanic should do that. That's the shade tree way and why those people later pay to have their bolts extracted lol.
 

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Ok, have done searches and my Google fu is weak. Doing my LCAs and I know specs are 190ft/lbs or 103 ft/lbs + 135 degrees. My question is can I use the impact to torque them down. My line of thinking is torque to 103 with wrench then mark the bolt so I’d know when I hit 135 degrees and use impact from there till hit the mark. Have a Milwaukee M18 Fuel 1/2 impact. The big boy. Have breaker bars etc. just trying to avoid that route and use the impact if possible. Have never had to torque anything to these specs so figured I’d best ask opinions. Thoughts? Dangers?
With that impact, I wouldn’t advise trying to hit 190 ftlbs, because on setting # 4 it will blow past it and all of the sudden you’ll have the head of the bolt on the floor. Ask me how I know, lol….. set it on #3 take it down till it hammers but doesn’t turn, that’s about 160 ish, finish with wrench as others have said.
 

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mwilk012

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The German method, gütentite
If it makes people feel better you can stick a torque wrench on it afterwards and verify no movement at spec. Functionally, a bit over tight does nothing by but stretch the bolts.
 

Mikester86

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I just torqued all my control arm bolts to spec last Thursday. Buy or rent a torque wrench that will handle at least 190 foot pounds, then buy or borrow some auto ramps. Drive the front end up on the ramps and torque those suckers to 190 foot pounds. The ramps made it so much easier to get some leverage. You will feel a great sense of accomplishment and relief knowing it’s all to spec.
 

Pinion

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The German method, gütentite
I have two torque wrenches, and still use this one the most.
You can always put a couple drops of blue loctite on the threads if you're overly concerned.
 

Carolina Jeeper

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Don't use an impact gun on it for final specs. Those bad boys are hard to control at that point. You'll likely have a two piece bolt if you try it.
 
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andrew4fins

andrew4fins

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Awesome. Exactly what I was thinking in back of my mind. I have ramps and a 250 ft/lb torque wrench. Just have never tourqued to this high of a figure. I always just used impact or air socket to run bolts on then finished up with the torque wrench. Looks like I’ll be going that route here as well. I did know not to use the #4 setting on impact. That looks to be a bolt killer for sure. Thanks everyone for your responses.
 

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DadJokes

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I did the 130 & 135° method with an impact. I didn’t have a torque wrench that went that high AND didn’t have a lift to make it easier to achieve with the tools I had. I went and bought an impact that a YouTube channel used on their LCA install.

As long as you measure the start and mark and stop point (bolt head mark and frame side mark) accurately, it will be accurate if you stop exactly where you should. It’s about bolt stretch to maximize clamping (not the final measurement of friction under the bolt head/nut while not going further than necessary and just elongating the bolt, not increasing the clamping, and potentially causing future failure. That is why they recommend just replacing the bolts, to mitigate extra bolt stretch and fatigue from repeated torquing. That…and that they might be a little over done at the factory and the lawyers want the company to cover their butt.

Trained machinist here. Using the impact is fine. Sneak up on it.
 
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XxsullyxX123

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I just torqued all my control arm bolts to spec last Thursday. Buy or rent a torque wrench that will handle at least 190 foot pounds, then buy or borrow some auto ramps. Drive the front end up on the ramps and torque those suckers to 190 foot pounds. The ramps made it so much easier to get some leverage. You will feel a great sense of accomplishment and relief knowing it’s all to spec.
that's how I did mine. ramps were essential to get any leverage
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