Need Another Flexplate

[cucvcan]

My flexplate is going again. I can hear it. This is the second one this year. Has anyone ever put any sort of stiffner or reinforcing bracket on their flexplates? I read here where a guy suggested it but there was no followup on wether it solved the problem. Could a bad harmonic balancer affect the flexplate? What about towing, I did pull a hay wagon the weekend before but I am always careful to keep my RPM's low. I am running 33" tires with stock gears in my m1009. I don't see how gearing could be part of the problem as the flexplate is used for starting.
Thanks

 

[T_F_E]

You dont really want low rpms because you could be lugging it and raising egts to much which is harder on the motor and economy

 

[dmc-4359]

Run your engine with your dust cover off. Could be that the transmission is not keeping the torque converter straight and that is letting everything go to ****. Also, before when I thought I'd burned up my second flexplate in a year the smart characters here (who diagnosed my first bum fp) said I should check the drive train mounts. Apparently I was just being paranoid at the time because it has been several months without any further developments.

 

[cucvcan]

Will do dmc-4359. I'll take a better look at the engine and tranny mounts. I'm also going to add a block heater. I think that the way I start it in the winter (visor instructions) is rough on the starter and the flexplate.

 

[Tanner]

Are you running the rear brace on the starter? You might be 'ballooning' the torque converter if trans temps are getting too hot - this could lead to bending/bowing of the flexplate... and use a GM factory flexpate (in case you were using cheap Chinese replacement from parts house)

'Tanner'

 

[ODdave]

Are you running the rear brace on the starter? You might be 'ballooning' the torque converter if trans temps are getting too hot - this could lead to bending/bowing of the flexplate... and use a GM factory flexpate (in case you were using cheap Chinese replacement from parts house)

'Tanner'

there is an alignment issue somewhere between the trans and engine, CLEAN the mating surface and make shure your alignment pins are instaled properly, not to far into the engine block. ballooning may be and issue also. one more thing to look at, when you unbolt the converter, can you push it back about a quarter inch easily? dose it have a gap w/o pushing it away? if so there may be an interferance in the converter to crank centering hub. just some thoughts

 

[DMaddox]

you said you could hear it ,, i know its hard to describe a sound but is it a kind of high pitch rattling sound? i looked a m1009 the other day and it ran good but at idle it had that rattle sounded sorta like the exhaust but everthing was tight.

 

[cucvcan]

Thanks all. I will take a look this weekend. The brace is on the starter. I'll have to investigate the alignment issue further.

The sound is like a scraping/rattling sound. When it first happened I thought a exhaust manifold had broke/cracked. That was not the issue and it just gets worse. Almost sounds like the tranny inspection cover on the bottom is dragging under the truck. It sounds scary like its the end of line for your 6.2.

 

[dstang97]

I had a bad torque converter that would wobble and crack the flex plate arond the 6 bolts near the crank.

 

[dstang97]

I had a bad torque converter that would wobble and crack the flex plate arond the 6 bolts near the crank.

 

[1stDeuce]

I had a metallic sounding noise coming from the flexplate/inspection cover on the truck I put a 700R4 in. Turns out one of the torque converter bolts had backed out of and was starting to cut a groove in the inspection cover. Might want to drop that baby quick and see if that's all it is!
C

 

[DMaddox]

Thanks all. I will take a look this weekend. The brace is on the starter. I'll have to investigate the alignment issue further.

The sound is like a scraping/rattling sound. When it first happened I thought a exhaust manifold had broke/cracked. That was not the issue and it just gets worse. Almost sounds like the tranny inspection cover on the bottom is dragging under the truck. It sounds scary like its the end of line for your 6.2.

Could you here this sound all the time? or just when the truck was at idle.. the reason I'm asking is because I test drove a m1009 the other day and at idle it made a sound similar to the one you are describing, however as soon as I increased the rpm's slightly the noise went away, I though it may have been loose exhaust but I pushed against the pipes,, both side with my foot to dampen the sound but all was tight.. this truck is super nice the body is straight with no rust inside or out , it has 87,000 miles for $2400 on a buy here pay here lot..

 

[cucvcan]

You can always hear the sound. You can even hear it when the starter is turning it over. When the flex plate first starts to break you will not hear it when you gun the engine. When it was under load you don't hear it but coasting down hills, what a racket. There not that expensive $90. I just can't figure out why I'm replacing another after only a month and I wondered if anyone thought towing/gearing could be related. I'm getting the torque converter looked at by someone who I hope will be able to determine if that is my problem.
I also wonder if the 24V starter is harder on these flexplates, as they were designed for 12v.

 

[dmc-4359]

You can always hear the sound. You can even hear it when the starter is turning it over. When the flex plate first starts to break you will not hear it when you gun the engine. When it was under load you don't hear it but coasting down hills, what a racket. There not that expensive $90. I just can't figure out why I'm replacing another after only a month and I wondered if anyone thought towing/gearing could be related. I'm getting the torque converter looked at by someone who I hope will be able to determine if that is my problem.
I also wonder if the 24V starter is harder on these flexplates, as they were designed for 12v.

They aren't designed for a voltage, just a specific torque. If it were the starter causing the issue failures would present in the ring gear where the two interact. In our case, the flexplate itself is designed to handle well over 250 ft/lbs so the 50 ft/lbs or so that the bendix gear is putting against it would hardly be noticed from a metal fatigue perspective.



edit - I should apologize for a bit of misinformation. I figured the torque output at the rated output of one of our starters and the 500rpm we use to get our engines started.

Torque * RPM/5252 = HP

DC motors make their maximum torque just after 0 rpm so likely the initial torque hitting the flywheel is closer to 150-200 ft/lbs though the calculations for what they would actually be doing is stuff I have long forgotten from my classes.

 

[cucvcan]

All bolts were tight (used loctite last time). Flexplate is breaking all the way around the bolts (like a big donut), almost like the starter is putting too much load on and causing shear. But there is no problem with the teeth on the starter or the flexplate. Torque converter seems good. Alignment looks good and engine/tranny mounts are all tight. I guess I'll install the new flexplate and cross my fingers that I don't have to do this again in a months time.
I'm still toying with the idea of reinforcing the flexplate, but I don't want to break something more expensive. My flexplate might be acting as a shear bolt right now, so I will just reinstall and monitor.

 

[dstang97]

replace both torque converter and flex plate and be done with it.

 

[cucvcan]

Problem appears to be with the end of my crankshaft. It is warn and rounded over and does not give a good seat for the flexplate to sit against. I need to replace the crankshaft, or I am going to have to get another engine (350 gasser?) or another 6.2.
Has anyone ever replaced a crank on these from under the truck or should I pull the engine?

 

[jimm1009]

If the flange was actually bent out of round that is one thing but if it simply has a ding on it and is still true to the crank then remove the ding with a dremel or die grinder and you should be good to go.

 

[cucvcan]

The outer edge is rounded. I am thinking of building it up with some weld and then grinding it down. Don't really want to replace the engine because it runs and starts so good. Maybe dstang is right. The torque converter may be wobbling (it is a rebuild) and causing this stress on the flexplate which is affecting the end of my crank.

 

[beanman1]

ok i think i am having the same problem i thought my engine was knocking so i got out my stethiscope probe and listned noise comong from dust cover . i took off the dust cover and checked the torque converter bolts 1 was loose so i tightened it but i still have the sound ( sounds like engine is knocking but a little quiter i guess)