I just put a 357 in my 89 GTA. Bought a new flex plate with the counter weight cause I have the 1pc rear main. Turned it over and fired right up but had a horrible vibration. If you were sitting in the car your teeth would probably chatter. Got under the car unbolted the torque converter and noticed my flex plate was wobbling. Not anything extreme but it was surely noticeable.

Would this cause the vibration?

 

loose flexplate bolts will cause it to to make all kinds of noise.There might be a glob of old thread locker in the holes. not letting the bolts seat. pull them, chase the threads, and retorque.

 

I took a impact to all of them and went over them a second time. Just pulled the flex plate off and it does seem a bit warped. The counter-weight goes towards the engine or towards the transmission? My flex plate isn't marked for whatever reason.

 

impact huh? thats a problem right there. the bolts need to be properly torqued, not hammered on with an impact gun. That can warp it.

take it back a try to get a new one for this "defective" one

 

65 pounds torque for flexplate bolts. Using an impact is bad. Same goes for wheel nuts. You can use an impact to quickly zip them up but don't use it to tighten.

Wobbling flexplate. Warped from using an impact or not aligned on the dowel (if there is one for a one piece rear main crank). If there's a counterweight then the flexplate should only go one one way. The only way that's possible is with a dowel pin or the holes are drilled so that it can only line up one way.

If you look at the flexplate, the mounting holes for the torque converter should have a raised area around the holes. These point at the torque converter.

 

Took it back, they changed it out with no problem. I kinda figured the impact wrench was probably the issue. Hope I didn't mess the engine up!!

Should loctite be used? Or is it okay to not be used?

Also, is there a sequence to the bolts? Or just go around?

 

I use red loctite on mine. Blue is probably fine.

 

Alright. Used thread locker and TORQUED the bolts down with a torque wrench.

Lesson learned for sure. Have yet to fire it up due to my intake being off. Should know something by tomorrow.

Thanks!

 

When you bolted on the flexplate, how much did the torque converter get pulled out of the tranny, if any?

 

The torque Converter getting pulled out can cause vibrations because it is not properly seated inside the front pump.

 

The TQ was pulled up but just a hair. I unbolted the TQ and pulled it back away from the flex plate and after getting under the car and looking, it was evident that it was infact the flex plate. It was wobbling.

 

Look at your torque converter. How much can you bend its bolt pattern?

Look at your flex plate. How much do you suppose it would bend if it was bolted up to something as solid as a torque conv of any particular shape?

Look at the name "flex plate". Why do you suppose it was named that?

Look at your crankshaft. You'll notice that it has a sort of rib sticking out around it, with the hole in the middle about 1¾" or so in diameter, just the right size for the pilot (wonder why it's called that? ) on the TC to fit into it.

The way it's SUPPOSED to work, is that the flex plate is SUPPOSED to be sort of like a spring washer, set up a bit too far toward the engine at rest; and it's SUPPOSED to pull the TC out of the trans and up to the crank. TC <-> crank is the alignment feature, NOT anything to do with the "flex" plate.

A "bent flex plate" is non-existent, once it's been bolted to a TC. Whatever your problem was, that wasn't it. Glad you got it fixed though, but it sure sux to be the people that now have to re-package a perfectly good FLEX plate and put it back into stock.

 

Did you read above where I stated I put it on with a impact wrench originally?

Aren't these supposed to be torqued to a specific torque?

So let me get this straight. If a flex plate is wobbling due to improper installation, that wouldn't cause a imbalance?

 

It's FIXED!!!

Sure enough I torqued the FP down with the proper settings and no vibrations

NEVER will I go crazy with a impact gun again!!