1356 Helicoil

[jaluhn83]

Got a 1356 tcase with 5 of the 6 mounting bolt threads stripped - is there enough meat on the case to heli coil them or do I need to find a new case front?

 

[SDEconVan]

A helicoil done correctly has more clamping force than OEM. The coil/threads are larger diameter and distribute the load over a greater area. I do them all the time, recommended!

Check out #147

http://www.oilburners.net/forums/showthread.php?69057-1998-E4OD-on-the-outside-wait-a-minute!/page10

 

[jaluhn83]

Understand that, my concern was if the casting is thick enough to handle the hole being drilled out for the insert - if it's thin there to begin with then there might not be enough material to have sufficient strength after the hole is drilled out. Wouldn't worry about it as much in cast iron, but in the soft alloys and with as much stress as there in on the bolts it's worth asking the question.

 

[SDEconVan]

The link I show has heli-coils going into very soft/mushy alloy. Your 1356 has a magnesium half and aluminum alloy half. Most of the holes have enough material to accept an insert. There are one or two that are out on the perimeter of the case, on extended bosses that are close but still I think you will come away with a stronger situation with the heli-coil if done correctly.

 

[SDEconVan]

Oh, BE SURE to use an inch-pound torque wrench, not a foot-pound wrench and dividing the torque value by 12, too chancey,
I've had to correct other people's hack work with heli-coils more times than I'd like to mention, like nut/bolt fixes, JB-Weld and worse...

...heli-coil is the right/best choice, short of welding/fill and re-tapping.

 

[hce]

Heli coil taps remove very little material compared to a regular tap, which will help prevent cracking if it is thin. Once the tap is run there should be little worries. I recommend cleaning the hole out after tapping and install the heli coil with loctite. I have had heli coils back out. Make sure to lube the bolt to prevent loctite adhering to the bolt and helicoil.

 

[riotwarrior]

Less he has a 1 ton 1356 w PTO provision...then it is all magnesium.

Only the 1356 PTO case half is made of aluminum fyi to best of my knowledge

 

[rotarydragon]

Heli coil taps remove very little material compared to a regular tap, which will help prevent cracking if it is thin. Once the tap is run there should be little worries. I recommend cleaning the hole out after tapping and install the heli coil with loctite. I have had heli coils back out. Make sure to lube the bolt to prevent loctite adhering to the bolt and helicoil.

Seconded. I've had this happen on several Type III engines.