How much should a flex plate flex?

[FSJNut]

I took my torque converter inspection cover
off last night and found that the bolts that
hold the flex plate to the converter have
been hitting the 1/16" plate that goes between the trans and the engine. I had been hearing a noise on hard acceleration that
has been getting gradually worse over the last year. It looks like there is about 3/16"
clearance on all four bolts, but somehow the
bolts are hitting this plate under acceleration. The top of the bolt heads are worn off, and there is a spray of metal shavings on the flex plate next to the bolts.
The plate checked flat with a straight edge. Is the flex plate supposed to flex this much?

[RudyC]

cONTACT "SCOTTY" since he said there is some bushing in the crank shaft, maybe it keeps it from flexing too far forward.
but first use a light and look closely around where it bolts to the crankshaft. look for cracks, the flywheel may be broken or your torque conveter may be bad and be causing it to wobble.
Thats what happened to me. my three torque converter bolts were scuffed on the top too and i saw my flywheel was broken so I HAD it replaced. four months later it broke again. This time I dropped the tranny and replaced the flex plate myself. Well it started tapping the bolt heads again and this time there was a squeeling sound. it turned out that my torque converter was bad, the bearings went out in it. and was off balance. the stupid repair shop didn't check it first time. the second time i changed the flywheel myself and thought it was ok. well it went out on me last month and had to replace it and the tranny pump. Of course since i had to drop the tranny anyway i put a ne Q trac chain in too. Run it with the cover off and look under it see if the T-Q and flex plate wobble or looks off balance. If you do have to change the flex plate get a new T-Q also I had to drop the tranny THREE times because of it.

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AKA RUDY79.
1979 WAGONEER, 360, TH400, Q- TRAC. 3" ADD A LEAFS, 31" MUD T/A'S (PEP BOYS CLONES).
" Go farther, it only breaks on the street"

[FSJNut]

I'll take a look at the flex plate "in action" tonight. That sounds like a good idea.
Rudy, do you think the real cause of all your flex plate woes was the TQ all along?

[RudyC]

On mine yes.
The first time i heard what sounded like ball braings rattling around the cover. It got worse after a day and I checked the T-Q to plex plate bolts and they were scuffed on the top. I replaced them with shorter head bolts. I figured the bone head PO put what ever bolts he had. I was ok for two days then it was suddenly worse. This time i looked closely and saw the broken "spokes" since they look like wagon wheels where the flex plate connects to crankshaft. I was too new for FSJ's then so I had it fixed $250 labor and 112.00 for new flywheel.
Four months later same thing, it broke again. I thought maybe it was the Quadra jet carb I installed was making too much power for the week flywheel. This time I dropped the tranny myself and found a used flyweel, but stupid me, I didn't think it was the T-Q and I just blamed the mechanic thinking he just installed it wrong. so I reinstalled the flex plate and old T-Q.
Well it was still off balance and then a month ago itstarted making whirring sounds and it got louder. It now sounded like the Jetsons car. I then dropped the tranny again and the T-Q had gouged the outer shaft of the Tarnny pump. I stuck my finger in the T-Q and felt some pieces of metal. Well it turned out a bearing or two failed the insides of the T-Q were bouncing around pieces of bearing were flying around inside. The vibes were causing the flex plates to break. I just reinstalled my tranny and a rebuilt T-Q and a good used tans pump and its fine now. In fact it's stronger now, I thought my tranny was worn but it was my T-Q slipping.
Since a good rebuilt one only costs about $100.00 and it's such a pain to drop the tranny, change the T-Q if you have to change the flex plate.



------------------
AKA RUDY79.
1979 WAGONEER, 360, TH400, Q- TRAC. 3" ADD A LEAFS, 31" MUD T/A'S (PEP BOYS CLONES).
" Go farther, it only breaks on the street"

[scotty]

excellent advice from rudy. the fles plate definately should not flex enough for bolts to contact.id put my money on a bent/cracked or broken flex plate. the torque convertor is balanced when it is built.anyting that changes the balance will cause vibes that will eventually destroy the front pump,as rudy found out the hard way. this can be anything from something bad in the convertor to trying to add a drain plug to a T C that didnt come with one.

a 727 T C can be found for $40 to $120,a th400 one prolly about the same.if you wheel it at all,wait for them to build you one with a drain plug,it shouldnt cost more,and is well worth it-i waited an extra day form mine and that drain plug has saved my tranny from water destruction several times.

id replaace the TC if youve got to take the tranny out.also check the front pump,and put a new seal in it. if you take it in deep water,run the vent line up high. i think the th400 allready has a fitting that you can put a hose on.the 727 will require the vent behind the TC to be plugged,and a new one added to the top of the case.

good luck-



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scott
85 grand wagoneer
258 with motorcraft 2bbl/904/twin stick dana 300/dana 44/welded amc 20
38x15.5 gumbo mudders
snorkel/dual batteries/onboard air/"custom" convertable
3 inch body lift/mostly stock suspension/"modified" fender openings
custom front/rear bumpers and brushgaurd

T18/dana 20 swap very soon
searching for dana 18 to replace the 20...

[FSJNut]

Thanks Rudy for the suggestion to take
a look at the flex plate while running.
Last night I got a helper to run the engine
at different RPM's while I looked at the flex plate. Everything normal, no bolts hitting,
no nothing. Then I had him let it idle and
put it in drive. I couldn't believe what I saw - the entire spiining assembly, flex plate, TC, crankshaft, flywheel pulleys, etc,
moved forward 3/16"! When he put it back in neutral it stayed forward for a second or two, then moved back to the normal position.
It was obvious that if the throttle had been opened more it would have moved forward enough for the bolts to hit the engine.
I've seen quite a few engines but never one with nearly 1/4" endfloat.
Now comes a bunch of new questions like -
what would cause it to have this much endfloat? what is most likely trashed in the engine/trans (bearings, crank, block, TC,
front pump).
No matter what, it sounds like it hase to come out of there.
Any suggestions at this point would be greatly appreciated.

[RudyC]

That sounds like a lot. The crank should not move like that. sounds like crankshaft or bearings, either way engine rebuild.


------------------
AKA RUDY79.
1979 WAGONEER, 360, TH400, Q- TRAC. 3" ADD A LEAFS, 31" MUD T/A'S (PEP BOYS CLONES).
" Go farther, it only breaks on the street"

[This message has been edited by RudyC (edited October 19, 2000).]

[Blue Woody]

Your main bearing (including the one that controls crankshaft endplay) are most likely shot. My contact at Chrysler says this was a common problem. Just replaced my whole engine with a Jasper reman since I had the same issue (plus a host of others too). You can get away with replacing just the main bearings and I'm told you can do it without removing the engine from the vehicle or the crank from the engine. Have fun!