Use of Helicoils for thread reconstruction

[Photon440]

Dissimilar metals do not gall, similar metals do. Similar metals will micro weld and that is how galling starts and only gets worse the more you turn it. Aluminum threads are pulled/destroyed by over torquing and repeated torquing. Once the thread is damaged, it is going to rip out. A Heli-Coil is a great repair for aluminum threads as they are usually a low torque application. In my opinion, Heli-Coil inserts, depending on size and material they are inserted into, should be limited to about 45 ft/Lb. A Time-Sert is a great repair also but requires more steps to install. I use them often as my go-to repair, but there are times when just a Heli-Coil will work. Time-Serts are also the only proper repair for a damaged/oversized hole by using a "Big-Sert" repair insert. The insert OD is larger to fix the oversized hole, but it is thicker to go back to the original thread size.

Galvanic corrosion is also a major reason for seizing when dis-similar metals are fastened, usually mitigated by using anti-seize compound which acts as a sacrificial anode.

 

[PROSTOCKTOM]

Year ago when I worked in a transmission shop hardly a day would go by that we didn't have to install Heli-Coils in pan bolt holes.

We would do a service on a Ford AOD/ AODE transmission and end up installing 3-4 Heli-Coils before it was over.

Read the instruction and watch a couple of YouTube video if you're unsure, but you really have to try hard to not get them correctly.

My boss would always say, "If the factories would just spent twenty five cents worth of anti-seize on a car our job would be a lot easier."

Tom

 

[Sixpactogo]

In all of my years of wrenching on cars and trucks I have to say I never needed to use a Heli-coil til now. I have had the pan gasket off of a dozen 727 transmissions and never stripped a thread until this year. I was so impressed with the ease of installation and structural upgrade to the threads, I did all 14 of them.