Broken flex plate

[sdan27]

We had a Case 821 front end loader with a ZF 4WG-200 transmission. It had real low power and overheating the trans filter. We pulled the trans and found the flex plate was in pieces. The loader has nearly 10,000 hours on it so I figured it probably just came apart from fatigue over the years. I was wondering if there was anything else that could have caused the flex plate apart like it did that I should look at while its apart.

 

[pidster]

Check the starter. If it seized up suddenly or came loose putting it at an angle where its teeth and the flexplate's teeth dont line up straight that would certainly ruin the flexplate. I'm assuming this occured while running? A motor certainly wouldnt be able to start with a broken flexplate unless the starter is connected elsewhere.

 

[robshelton]

Typically, flex plates don't just break. Be sure to check the balancer as unwanted harmonics can crack/break the flex plate. I don't know if this applies to your loader, but an improperly shimmed starter can cause un-necessary flex and eventually cause flex plate problems too. If I'm wrong I know somebody will correct me soon. Good luck!

 

[JimPghPA]

Along with all the above, be sure to use a torque wrench to tighten the bolts to the proper torque.

 

[onion]

90% of the time, a broken flex plate is caused by loose flywheel housing or converter housing bolts. If you've already pulled the trans, then you would have noticed whether or not the converter housing bolts were loose. Also while you're at it, check and make sure that the bolts holding the flywheel housing to the engine are tight. Look closely at the motor mounts too.

And check the vibration damper- these are a simple design, and it will be obvious if the thing is bad. Check and see if the rubber is swelled (from oil) or cracked... make sure it isn't wobbling. With 10,000 hours- it might be a good idea to replace the thing anyway.

But what has me puzzled is that you say the loader "had real low power and overheating the trans filter". I would think that a broken flex plate would yield NO power rather than just low power... and I don't know what to make of "overheating the trans filter". I have to wonder if there's some poor communication here, or if there are more underlying problems.

 

[Steve S]

Low power as is low end pulling or starting or pushing?

 

[SteveSRT8]

usually tend to crack first, if someone was listening they may have noticed before complete breakage.

X2 on the converter bolts. That and the bolts into the end of the crank are mega critical.

I wouldn't be surprised to find that the engine/trans are mis-aligned.

 

[sdan27]

I mistyped a little in my OP. I meant to say that the transmission fluid was overheating, not that the filter was overheating. There is the flywheel bolted to the crank on the engine and then the flexplate is attached to the torque converter in the trans and the bolts go through holes in the flywheel and fasten it to the flexplate. We have had issues with the starter not being lined up properly as bolts holding it in had come loose and fallen out. The ringgear is attached to the flywheel so I don't know if that could have negatively affected the flexplate like it did. I'll probably take the flywheel off and see what it looks like all around and then make sure the bell housing bolts are in there like they should be and torque the flywheel bolts like they should be. I'll check the vib. dampner as it should have two dowel marks that are supposed to be lined up and see what that looks like. Thanks to all for the advice.

 

[morris]

are any dowel pins missing?

 

[sdan27]

No dowel pins that I noticed. I don't think there are any between the engine/trans like I've seen on other appications. I did check the alignment marks on the vibration dampner and they were lined up like they should be. It was kinda crazy that when I took it apart, the flex plate was cracked in several places but was still holding together until I grabbed it then it came apart in pieces.

 

[sdan27]

I got back around to it and took the flywheel off and found a chunk of the bell housing was cracked/missing. It was kinda right behind the oil pan so you couldn't tell from the outside without taking the flywheel off. Found another used one for $300.

 

[morris]

back in the dark ages i bought a 1963 chrysler 300J with a 500 ic stage 3 heads, intake ect. the flex plate came apart on the way home, did drive it home. it was missing the dowel pins. put new pins in, never any trouble after that.