torque convertor bolts keep coming loose.

[Crewchief]

I have 70 Challenger with 512ci. big block; 727 transmission, race full flexplate, YANK torque convertor. The car is a dedicated autocross car so I am in and out of the throttle all the time. I keep having torque convertor bolts loosen up then it starts making knocking noise. I have tried red loctite and they still loosen, I am not running any type of lock washer. I am using the bigger size bolts. HELP.

 

[MoparCarGuy]

Loctite and proper bolts with correct torquing should not have this problem.

 

[Xcudame]

Using the 7/16-20 bolts with red Loctite and torquing them to 65 ft-lbs and they coming loose? Just asking because if so, I'm not sure of a fix.

 

[Crewchief]

Yes on red loctite and 7/16 bolts, I have used various torques, with and without torque wrench. Will try 65ft lbs. this weekend.

 

[Ricks72Chlgr440]

Are you using 12 point ARP bolts? If so with the loctite and they are still coming loose the only thing left is there must be something wrong with the TC threads.

 

[540HemiCuda]

I have seen guys tack weld the converter bolts after everything else failed to keep them from coming loose. Then, the flex plate starts to crack. The issue causing this that I have seen is that either the snout on the converter is just a smidge too large for the register in the crank or the register in the crank is too small. Which ever one is not original is the likely culprit. When the converter is held out just a little bit because the snout cannot go into the crank far enough, then the flex plate is flexing too much each rotation.

The other thing that can cause the bolts to loosen is if the tranny is not perfectly aligned to the block. I have not seen that much myself, but there used to be offset dowels to replace the originals so that you could square the tranny and block.

But with all the aftermarket cranks and converters out there now, that relationship is where I have seen the most problems. And in my experience, it is usually the converter snout that needs attention.

 

[Xcudame]

Be sure to use a beam torque wrench. The click ones are usually off! As long as the needle is pointing at ZERO when you start, you'll always be accurate.

If it still happens, @540HemiCuda is on the right path, start looking for parts not meshing together correctly.