Flexplate bolts came loose

[-83MONTESS-]

So I did the first oil change on the new 496 2 days ago and had it running for about 10 minutes that night. Fast forward to today I start it up everything is normal but I have a HORRIBLE knocking noise. I immediately thought my brand new engine is junk. I noticed that the knock went away as I increased the rpm. Check the oil pressure and its normal. 40 psi at idle and with a blip of the throttle it hits 80 psi so that put my mind at ease.

I climb under it to check the torque converter bolts and as I put a wrench on one of the bolts the entire torque converter and flex plate rotates about 1/4" on the crank!!! I can literally wiggle the TC and flexplate by hand back and forth. So now I know I gotta pull the transmission back to re-tighten the bolts but my question is what would cause flex plate bolts to randomly loosen? It was fine one day then the next day it's knocking like crazy. They are 12pt ARP bolts torqued to ARP's specs with red lock-tite. The flex plate is an externally balanced Scat plate that came matched with my rotating assembly. Any ideas???

 

[RegalBegal]

Gremlins. LOL

Seriously, you may have had some junk between the flex plate and the crank that worked its way out.

 

[pontiacgp]

I don't see how they came loose if you used thread locker on them. Where the threads clean before you installed the bolts, maybe there was oil on the threads. With locktite thread locker you raise the torque value by 10% to break the torque. They started using loctite on aircraft decades ago and I went on a seminar about the product and it's the best method of locking a bolt. As far as tightening them I think I remember you can can tighten them without sliding the transmission back.

loctite has a cleaner for the threads if you need it...'

 

[-83MONTESS-]

I don't remember having any issues with the threads. The more I think of it the more I question whether or not I Lock-Tited them or if I just used the ARP lube. It's been a long time since I installed them.

Im hoping that if I unbolt the converter I can slide it back enough to take them out. Im kind of tempted to just pull the trans and send it off because it still randomly pukes out of the vent but that's a whole other issue.

 

[williamattop]

We need to get priest to perform an exorcism on your car to get ALL those demons out so you can start enjoying that machine.
The way I see it, if you put some lock tite on or not, this still should not have happened.
I cant help but to think if they came loose that something rotating is out of balance. *ss-uming everything was toqued to spec when newly installed.
Hmmmmmm,,,, how many miles on this install so far? Is there any kind of coating on the flexplate?

 

[-83MONTESS-]

There is a coating on it. Not sure if it's paint or powder coating. Whatever Scat uses. Maybe 50 miles total and lots of garage run time like break in and tuning. I just did the first oil change on friday. Had it running friday night and everything was fine. No sounds or vibrations. Car sat all day saturday and wasn't fired up until sunday which is when this became evident.

In an old thread I brought up a slight vibration above 4k rpm in every gear. I thought it was my trans crossmember not being mounted rigid enough so I braced it up. I also heard from a few people that with solid engine mounts and body mounts odd vibrations were to be expected. The only thing I can remember about the flex plate install is that when I installed the transmission for the first time as I was tightening up the converter bolts I heard a loud pop. I thought it was the flex plate bowing out like the converter wasn't flush on the flex plate and the tightening of the bolts popped them together. That was with the junk B&M converter I ended up swapping out later on.

I won't be able to tear into it for a few days but im going to pull the flex plate off and check it for flatness. Im hoping I can get it on and off without pulling the transmission again. If the flex plate is flat and the bolt holes aren't dicked up I will be sure to scrape the paint/coating off of the area surrounding the holes and use red lock tite on the bolts.

 

[-83MONTESS-]

Well after climbing under the car and removing the converter bolts I have come to the conclusion that there's no way I can tighten the flex plate bolts with the trans in the car. I'm not too bummed because that gives me an excuse to get the trans gone through while it's out and put my mind at ease. I just hope if the trans needs rebuilt it didn't mess up my brand new Hughes converter.