What went wrong? flex plate, converter, or tranny?
#1483560
08/12/13 10:16 PM
08/12/13 10:16 PM
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Joined: Jul 2013
Posts: 116 Pa
71nonRT340shaker
OP
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OP
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Joined: Jul 2013
Posts: 116
Pa
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I have had a nasty vibration in my car since I got it running. I put about 200 miles on it 2 years ago, the tranny mount was shot so I put a new one in hoping the issue would go away, and it got 20 times worse. I haven't really driven it more than in and out of the garage when I want to work on a DD since. The car came from a guy who built it in 83, and parked it a few years later. I have no idea why it was parked he said his kids were born and that was that, maybe it had other issues so wasn't driven any longer? Beats me, it came with a Mallory dual point set up, but the dist. was gutted. I never heard it run before buying it 7 years ago.
The motor is smooth as can be at idle, it doesn't shake at all with your hand on the valve covers. Around 1500 - 1800RPM it starts to shake on the inside and its not comfortable to even sit in, it rattles your teeth. Here's the front of the flex-plate, and it appears the left ears on the stock plate (looking at from the front of the car) are bent. What does a flex plate failure look like? I have heard they crack, would that cause this issue? Obviously the plate is damaged but could it be the tranny/converter?
The motor is a 9-9-68 casting 340 with the early (thinner) dampener which I already swapped with another one I had, the converter doesn't have any weights welded onto the flat spots. I thought this was all correct maybe I'm wrong? It's a 727, and it vibrates in park, neutral, and all forward/reverse gears. Timing is set at 28 or 30 flat with no vacuum advance, electronic conversion Evan's harness and MP dist, orange box.
Thanks in advance, TC...
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Re: What went wrong? flex plate, converter, or tranny?
[Re: stumpy]
#1483564
08/13/13 12:46 AM
08/13/13 12:46 AM
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Joined: Aug 2003
Posts: 43,303 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,303
Bend,OR USA
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Last edited by Cab_Burge; 08/13/13 01:44 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: What went wrong? flex plate, converter, or tranny?
[Re: 71nonRT340shaker]
#1483566
08/13/13 01:49 PM
08/13/13 01:49 PM
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Joined: Aug 2003
Posts: 43,303 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,303
Bend,OR USA
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Quote:
Thanks for the quick replies. The plate is almost certainly on backwards, it all makes sense because the mounting holes only allow it to line up one way. I'm sure having the holes offset because the plate is on backwards causes the whole deal to be out of round and therefore vibrate. It's amazing the guy I got it from never changed it around?
I'm not doing anything crazy with the car just want a jump in and go cruiser, I'm most likely going to order the B&M 10230 and some new bolts. With any luck the flex plate was the weak link and it didn't rough up the crank or back of the block. Maybe I can even get to drive this thing before the weather breaks.
I wouldn't , and don't, use the B&M flexplates now do to some guys having issues with them vibrating(the externally balanced ones) and the converter bolt holes not lining up correctly I would either buy a new one, if you need and want a SFI spec. one for racing, or go to a tranny shop or junk yard and buy a good used one I have a dozen or more of all three sizes( 11 and 12 inch bolt patterns, small and big converter bolt sizes) and types(6 and 8 bolt crank flanges) hanging on the wall, to bad your not closer
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: What went wrong? flex plate, converter, or tranny?
[Re: 71nonRT340shaker]
#1483568
08/13/13 04:51 PM
08/13/13 04:51 PM
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Joined: Jan 2003
Posts: 25,988 Rio Linda, CA
John_Kunkel
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 25,988
Rio Linda, CA
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You can't put a flexplate on backwards for several reasons.
The INTERNET, the MISinformation superhighway
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Re: What went wrong? flex plate, converter, or tranny?
[Re: John_Kunkel]
#1483569
08/13/13 04:59 PM
08/13/13 04:59 PM
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Joined: Jan 2003
Posts: 25,200 Upper Midwest
MoparforLife
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 25,200
Upper Midwest
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Quote:
You can't put a flexplate on backwards for several reasons.
I agree with you John. Virtually impossible to do to put on a flexplate wrong. The bolts would not line up on either the crankshaft or the converter.
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Re: What went wrong? flex plate, converter, or tranny?
[Re: 71nonRT340shaker]
#1483570
08/13/13 05:03 PM
08/13/13 05:03 PM
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Joined: Jan 2003
Posts: 21,085 Niles , Ohio
therocks
oh wait.but hey.lets see.oh yeah.
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oh wait.but hey.lets see.oh yeah.
Joined: Jan 2003
Posts: 21,085
Niles , Ohio
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Man that had to make a ton of noise from the looks of it.Oh and to the people that say you cant put a flex on backwards.Guess again.Had a guy at the shop that did on the Mittsy 2.6.He didnt think anything was wrong with all the bolts not lining up.But he put it in and had the motor all bolted together.It was a lot of work but he did it.After all these years I still wonder how.Rocky
Chrysler Firepower
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Re: What went wrong? flex plate, converter, or tranny?
[Re: therocks]
#1483572
08/13/13 06:03 PM
08/13/13 06:03 PM
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Joined: Jan 2003
Posts: 25,200 Upper Midwest
MoparforLife
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 25,200
Upper Midwest
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Quote:
Man that had to make a ton of noise from the looks of it.Oh and to the people that say you cant put a flex on backwards.Guess again.Had a guy at the shop that did on the Mittsy 2.6.He didnt think anything was wrong with all the bolts not lining up.But he put it in and had the motor all bolted together.It was a lot of work but he did it.After all these years I still wonder how.Rocky
You cannot do it on a big or small block. Bolt hols are offset on both the crank and the converter.
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Re: What went wrong? flex plate, converter, or tranny?
[Re: MoparforLife]
#1483573
08/13/13 06:42 PM
08/13/13 06:42 PM
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Joined: Jan 2003
Posts: 25,988 Rio Linda, CA
John_Kunkel
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 25,988
Rio Linda, CA
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Not only are the bolt holes offset but the flexplate is dished toward the motor, if you could get it on backwards the converter would be shoved back into the pump and the starter likely wouldn't fit.
The INTERNET, the MISinformation superhighway
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Re: What went wrong? flex plate, converter, or tranny?
[Re: John_Kunkel]
#1483575
08/13/13 07:05 PM
08/13/13 07:05 PM
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Joined: Jan 2003
Posts: 25,200 Upper Midwest
MoparforLife
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 25,200
Upper Midwest
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Quote:
Not only are the bolt holes offset but the flexplate is dished toward the motor, if you could get it on backwards the converter would be shoved back into the pump and the starter likely wouldn't fit.
Yep - many things that say you can't do it!!!
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