More Crossmember Problems...

[hokeymcf]

To make a long story short, i was reinstalling the crossmember and i ended up somehow messing up the threads on two of the four main bolts, as well as the threading that the bolts screw into.
i don't think they're stripped, they probably just need to be chased (is that what you call it?).
anyway, if anyone would be kind enough to tell me if this is something i can do by myself or with another person, or if i should have it taken to a shop, i'd be very grateful.
thank you in advance.

[bcp477]

If you cross-threaded the bolts.....and torqued them in very far, while trying to get them to seat, you've probably buggered up the threads enough to require more than just a bit of "chasing". (Yes, "chasing the threads" is the right term.) It is impossible to say for sure, without being there, but that is based on long experience. If you didn't torque in the bolts too far, you may be able to fix this with chasing.

You will need the correct tap for the threaded holes (to match the existing threads)..... and a suitable tap handle. If you are referring to the largest diameter bolts on the sub frame, then the tap and handle will be heavy duty, as the bolts are sizable. Then, you can TRY to chase the threads....and see if the bolts will seat properly. You MUST have at least 2/3 or more of the normal thread engagement with the bolts, in order for the assembly to be strong enough to be sure of it holding. So, if the threads are too buggered, then the result will NOT be safe, even if you manage to get the bolts to bite onto their threads. Re-tapping threads is NOT just a matter of cranking in a tap - it requires care and a good touch - INO, an understanding of the process. You might well be better off just turning this over to a mechanic, or someone with experience in this sort of thing.

If the existing threads are too far gone, the only solution is drilling, tapping to a larger size, then fitting new bolts. This is a serious structural application, so something like "heli-coil" to repair the threads is probably NOT up to it.

In any case, if you haven't done this sort of work before, I'd recommend you turn this over to someone who has - lest a bigger mess be the result.

[hokeymcf]

Originally Posted by bcp477

If you cross-threaded the bolts.....and torqued them in very far, while trying to get them to seat, you've probably buggered up the threads enough to require more than just a bit of "chasing". (Yes, "chasing the threads" is the right term.) It is impossible to say for sure, without being there, but that is based on long experience. If you didn't torque in the bolts too far, you may be able to fix this with chasing.

You will need the correct tap for the threaded holes (to match the existing threads)..... and a suitable tap handle. If you are referring to the largest diameter bolts on the sub frame, then the tap and handle will be heavy duty, as the bolts are sizable. Then, you can TRY to chase the threads....and see if the bolts will seat properly. You MUST have at least 2/3 or more of the normal thread engagement with the bolts, in order for the assembly to be strong enough to be sure of it holding. So, if the threads are too buggered, then the result will NOT be safe, even if you manage to get the bolts to bite onto their threads. Re-tapping threads is NOT just a matter of cranking in a tap - it requires care and a good touch - INO, an understanding of the process. You might well be better off just turning this over to a mechanic, or someone with experience in this sort of thing.

If the existing threads are too far gone, the only solution is drilling, tapping to a larger size, then fitting new bolts. This is a serious structural application, so something like "heli-coil" to repair the threads is probably NOT up to it.

In any case, if you haven't done this sort of work before, I'd recommend you turn this over to someone who has - lest a bigger mess be the result.

wow, thanks for the great advice.
i kind of already figured i'd have to turn it over to a mechanic for this when my dad told me about the precision required with using a tap. just thought i'd ask anyway.