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.

 

[Ronbo73]

Make sure the threads are clean and make sure the LocTite is primerless or not. If it's primerless you are ok. If it needs primer, then use it. If it is primerless do not use primer because it makes the primerless LocTite weaker. You really can't put to much on the threads because what isn't between the threads does not cure.

We use LocTite everyday where I work and have had representatives come to educate people on the "How to's" of LocTite.

 

[Crewchief]

Thanks for the replies, gonna clean all threads, loctite and retorque tonight,

 

[Bret Schneider]

Not sure if it was mentioned earlier, but make sure the bolts aren't too long for some reason. If that's the case the bolts would just be bottoming out rather than applying the correct clamping force when torqued down.

 

[pschlosser]

Not sure if it was mentioned earlier, but make sure the bolts aren't too long for some reason. If that's the case the bolts would just be bottoming out rather than applying the correct clamping force when torqued down.

the correct bolts are distinctive by the pattern on their heads. the OEM ones, anyway.
in most cases, our advice (and experience) applies to OEM setup, configuration and ... bolts.

 

[Bret Schneider]

Whatever... Guess you could just keep beating your head against the wall by doing the same thing over and over with the same results or take a step back and actually do some simple troubleshooting

 

[pschlosser]

Whatever... Guess you could just keep beating your head against the wall by doing the same thing over and over with the same results or take a step back and actually do some simple troubleshooting

thanks for you helpful advice, Brent.

 

[Katfish]

Not sure if it was mentioned earlier, but make sure the bolts aren't too long for some reason. If that's the case the bolts would just be bottoming out rather than applying the correct clamping force when torqued down.

Good input, I bought some ARP bolts that bottomed out in the convertor lug.
Had to hit them with an angle grinder to take a little off.

 

[Crewchief]

Just an update, I cleaned all the threads, added ORANGE loctite that I had never seen before, package says it holds 5x better than blue and is good for vibration looseness, torque them down. My son and I ran a local autocross this last weekend, 27 runs between the two us. My son qualified for the top ten car shootout and finished 3rd in the shootout. Beat out a bunch of Miatas, Subarus, Toyotas, corvettes, newer Mustangs etc. No knocking noise as of yet. Although I did find from coming loose the bolt areas are worn on the flexplate so replacement is planned in the future. Thanks for all the help.

 

[Crewchief]

Here's the beast. 4x time Moparty Grand Champion, multiple GOODGUYS autocross wins and SCCA class finalist.

 

[Katfish]

Good looking car, can you provide some info on the suspension mods?

 

[Crewchief]

Hotchkis TVS system, QA1 tubular lower control arms. B-body rear axle housing (narrower than E-body).
Wilwood 6-piston calipers front, 13" rotors, 4-piston rears, adjustable proportioning valve. Really agressive front end alignment setup.
Borgeson quick ratio steering box and quick ratio arms