Chevrolet Repair: tahoe broken flex plate, chevy tahoe, fly wheel

Question
i purchased a 99 chevy tahoe in feb 2004. in june 2004, the fly wheel was replaced. noting that the damaged part was not original. now in nov it broke again. what is causing this problem and can it be fixed? our mechanic says to get rid of it. i owe to much to trade it in. please help.

Answer
Hi Kim,
Lets take a little look.
First, you are not going to just dump it...you are going to replace the flex plate, so lets think some things out.

The only things that touch the flex plate are the torque converter, the crankshaft that the plate is bolted to, and the starter.
If the starter is causing the problem, you, or someone should have been hearing bad starter noises. Also, the ring gear should have some bad spots.  I don't think the starter is your problem...just keep it in mind.

Next, the torque converter. If it is the orriginal, I think I would replace it in a heartbeat. It could have one of the connector lugs crooked. It could be out of balance, although you should have heard or fealt that. It could be manufactured CROOKED, and be bending the flex plate every revolution. And the little center stub could be off center, or not fitting the hole in the crankshaft correctly. As a minimum, I would toss that converter and replace it.

Then there is the flange on the crankshaft that the flex plate bolts to. If it isn't perfectly perpendicular to the shaft, then the plate will be flexing every revolution.

Agreed...it is a FLEX plate. But they didn't intend for it to be bent constantly.

So if I were working on it, I would get a machinist straight edge, or a magnetic dial indicator base, or some other means, (and I would try several),and measure the runout of the crankshaft flange while rotating the crank.
I would then mount the flex plate and starter, and start the engine with the torque converter disconnected, so I could watch it go round, see if it wobbles, etc.

The last thing to check, and it would be hard to tell, but worth looking for, is if the transmission bell housing is machined crooked, which would cause the torque converter to operate on a slightly different axis than the crankshaft, or in other words, connect at an angle, which also would cause the flex plate to flex.

Most of that stuff a mechanic just doesn't look twice at when replacing a plate. But if he is aware of the history, those are the things to look closer at.

Good luck,
Van