cab mount problem!!!!!!

[eventhorizon66]

Then put a breaker bar on the nut and use some manual impact on the breaker bar with a 2-3 lb hammer.

Hey, we have the exact same impact gun!

[84chevysilverado]

well that sure makes sense bout the constant load breaking off bolts. darn wish someone woulda told me that earlier. we do have an impact its one of those electric ones that you can buy but i personally think they are only good for little jobs not good for big tourqe jobs

[Blazin]

I have an Dewalt electric impact, its got some sack. No matter how good the floor is I would use a hole saw and pop a hole in it. Then weld it up after. Or rivet a nice cover over it for future access.

[78 Chevyrado]

If you're turning the bolts with a wrech or ratchet, you might try an impact gun, it wont be as likely to break the welds as hand turning it.

 

If you don't want a powered impact, here's a manual impact wrench

[SUX2BU99]

If you can weld another nut on the underside, try that again.  Get a good bead on it, then soak the heck out of the captive nut with some weasel pee (as Blazin' calls it).  Then put a breaker bar on the nut and use some manual impact on the breaker bar with a 2-3 lb hammer.  My driver-side front mount bolt was so frozen that 5 minutes with an impact wrench didn't turn the socket any.  A half hour pounding on it with the method described above and I had it out in one piece.

You'll shear off even the hardest bolts by pulling with constant force, especially if you multiply the torque with a cheater-bar.  Most things can take pulses of momentary force forever without breaking but will yield and break under longer duration loads, even if those loads are less in force.  In short, impact is your friend.

This is very true about short impacts vs. constant force. This is useful too on rusted brake bolts like those on bleeder screws and wheel cylinder bolts. When I redid my rear brakes I used constant force to open a bleeder and busted it off. Same with one wheel cylinder bolt. When I tried just putting constant, but not heavy, pressure on my small ratchet and then used a rubber mallet to repeatedly strike the end of the ratchet handle, it eventually broke the bleeder screw and wheel cylinder bolts free without breaking the bolt heads. The constant pressure on the ratchet took away any slop in the mechanism to ensure the mallet strike was doing it's full work. It took a couple minutes but it worked.

When I took off my u-bolts to swap my diff, my impact gun was of absolutely zero use. 3/8" and 1/2" ratchets didn't budge them. Bought a 24" 1/2" breaker bar and that finally did it. It was a huge chore getting them off though. They did NOT want to turn!