Flexplate wobble - The 1947 - Present Chevrolet & GMC Truck Message Board Network

dave2953 · 01-02-2007, 11:08 PM

I had a broken flexplate in my truck that was making noise and replaced it with one I got from a friend. I installed it and ran the engine before I re-installed the trans. and noticed that the flexplate "wobbled" quite a bit as it was rotating. When you have it laying on a flat surface you can see that the flexplate doesn't lay flush all the way around. I went to the parts house and looked at a new one and it did the same thing. Is this normal? I guess it should have some movement, hence the name, but I don't know how to determine what's excessive. I just don't want to get it all back together and have complications. Sorry for the long post and thanks in advance for your help.

1968SWBBigBlock · 01-02-2007, 11:14 PM

I have a new one SFI approved heavy duty and it lays flat as can be. I would spend the $ and get a heavy duty unit. Lots easier than pulling that tranny again I promise!!!

**LockDoc** · 01-02-2007, 11:32 PM

-
I would think it should lay flat... I wouldn't use it on a bet.....

LockDoc

**kwmech** · 01-02-2007, 11:37 PM

Should not wobble at all. Get the SFI one

dave2953 · 01-02-2007, 11:44 PM

Can you get SFI at a parts house? I wonder if a board vendor sells them?

FarmTruk · 01-03-2007, 12:01 AM

Kind of a tangent here, Dave,

it is still on-topic...

What exactly does the "flex" in "flexplate" refer to? I've always wondered why it is called that, but never had a timely opportunity to ask. I know very little 'bout auto trannys.

dave2953 · 01-03-2007, 08:44 PM

It is called that because it "flexes" inward toward the engine. When you decelerate, the nose of the torque converter slides forward in the bore at the back of the crank. This movement causes the the plate to "flex".

Vince M · 01-03-2007, 10:02 PM

Once you bolt the flexplate to the torque converter it should straighten it out. You said you ran it without the tranny right.

*rage'nrat638* · 01-03-2007, 11:09 PM

call summit you can have a sfi one tommarrow for a extra 20.00.

FarmTruk · 01-04-2007, 02:22 PM

Quote:

Originally Posted by dave2953

It is called that because it "flexes" inward toward the engine. When you decelerate, the nose of the torque converter slides forward in the bore at the back of the crank. This movement causes the the plate to "flex".

Dave, Thanks for the description. That's one of those things that I have always wondered 'bout. I knew it was called a "flexplate" but just didn't know why.

68CHEBY · 01-04-2007, 04:51 PM

Most of the heavy duty units are a lot thicker in the center, on the outer ring is welded on a whole lot better

TraderJon · 01-04-2007, 05:36 PM

Not to steal a thread,but you got me wondering now ?
I just installed the rat motor & turbo 350 last night in the 67, I didnt pull the pilot bushing out of the back of the crank,motor had a 4 speed attached to it when i bought it,,,DID I mess up by not pulling the pilot bushing?
Thanks JFd

68CHEBY · 01-07-2007, 08:23 PM

The pilot bushing shouldn't effect anything, the convertor should still be able to fit in the crank with no interference.

Blue'72 · 04-02-2008, 05:48 AM

I'm going to resurrect an old thread.. Before asking my question, I decided to do a search.

Ok, to save time, skip this paragraph and go to the next.

I'm doing a frame off on my truck and do NOT want to have to come back and revisit anything after it's put back together. With all the problems I've had in the past and problems I've heard about with starters, I'm taking extra time making sure this new starter and flexplate are correct. I'm going from a 4 speed to auto, so I had to buy a new flexplate and starter. I adjusted the starter and then hooked it up to battery power so I could make sure it sounded ok. I noticed the flexplate is really wobbly.

So, what's the verdict? Will a wobbly flexplate cause any problems, or will it straighten out once the torque converter is hooked up and there will be no problems? I will spend the money on a good one if you think I should, but I really don't want to spend any more money than I need to.

01-02-2007, 11:08 PM	#1
dave2953 Dave's not here, man Join Date: Jun 2004 Location: Winder, Georgia Posts: 2,000	Flexplate wobble I had a broken flexplate in my truck that was making noise and replaced it with one I got from a friend. I installed it and ran the engine before I re-installed the trans. and noticed that the flexplate "wobbled" quite a bit as it was rotating. When you have it laying on a flat surface you can see that the flexplate doesn't lay flush all the way around. I went to the parts house and looked at a new one and it did the same thing. Is this normal? I guess it should have some movement, hence the name, but I don't know how to determine what's excessive. I just don't want to get it all back together and have complications. Sorry for the long post and thanks in advance for your help. __________________ - 2014 VW Jetta - 2015 VW Jetta - 1966 Ford F-250

01-02-2007, 11:14 PM	#2
1968SWBBigBlock Active Member Join Date: Oct 2006 Location: Ohio Posts: 1,643	Re: Flexplate wobble I have a new one SFI approved heavy duty and it lays flat as can be. I would spend the $ and get a heavy duty unit. Lots easier than pulling that tranny again I promise!!! __________________ 1968 SWB 454 + .040, 490HP x 540 FT pounds of Torque 10-1 Kb Forged pistons, recon rods w/ ARP wave loc bolts 781 heads Ported with 2.19/1.88 SSTvalves Lunati 60204 cam, Micro Trol lifters, Ported Edelbrock Performer Rpm manifold armor coated, Pertronix Triple Strike Ignition Holley 770 Street Avenger carb,Headers armor coated Built by Watson Ruppel Performance in Sarahsville Ohio. Hardshift Tranny Built Turbo 350,TSI 10" 3000 stall 12 Bolt Eaton Posi 4.10 Richmond Gears moser axles 18.5" x 31" Hoosier Pro Street Radials ET Classic 5 Wheels - polished Power Steering, Power Brakes,Disc Brakes,Tach & Gauge Dash, Tilt,Factory Air (gone) Custom Paint & Body Work Special thanks to my wife, my son and my money tree

01-02-2007, 11:32 PM	#3
LockDoc The Older Generation Join Date: Aug 2006 Location: Montezuma, Iowa Posts: 25,872	Re: Flexplate wobble - I would think it should lay flat... I wouldn't use it on a bet..... LockDoc __________________ Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 -

01-02-2007, 11:37 PM	#4
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,667	Re: Flexplate wobble Should not wobble at all. Get the SFI one

01-02-2007, 11:44 PM	#5
dave2953 Dave's not here, man Join Date: Jun 2004 Location: Winder, Georgia Posts: 2,000	Re: Flexplate wobble Can you get SFI at a parts house? I wonder if a board vendor sells them? __________________ - 2014 VW Jetta - 2015 VW Jetta - 1966 Ford F-250

01-03-2007, 12:01 AM	#6
FarmTruk In Memoriam... Join Date: Nov 2006 Location: Wallburg, NC Posts: 1,216	Re: Flexplate wobble Kind of a tangent here, Dave, it is still on-topic... What exactly does the "flex" in "flexplate" refer to? I've always wondered why it is called that, but never had a timely opportunity to ask. I know very little 'bout auto trannys. __________________ '68 C10 SWB 307ci 2BBL *FarmTruk Pics Here* *"You know, doing what is right is easy. The problem is knowing what is right."*

01-03-2007, 08:44 PM	#7
dave2953 Dave's not here, man Join Date: Jun 2004 Location: Winder, Georgia Posts: 2,000	Re: Flexplate wobble It is called that because it "flexes" inward toward the engine. When you decelerate, the nose of the torque converter slides forward in the bore at the back of the crank. This movement causes the the plate to "flex". __________________ - 2014 VW Jetta - 2015 VW Jetta - 1966 Ford F-250

01-03-2007, 10:02 PM	#8
Vince M Senior Member Join Date: Apr 2000 Location: Orlando, FL Posts: 1,076	Re: Flexplate wobble Once you bolt the flexplate to the torque converter it should straighten it out. You said you ran it without the tranny right. __________________ ............................................................ 68 Chevy CST SWB w/LS1, carb & 700r4. Golden Anniversary clone with a few improvements.

01-03-2007, 11:09 PM	#9
rage'nrat638 Account Suspended Join Date: Mar 2003 Location: THE FALL GUY CHICAGO IL Posts: 5,883	Re: Flexplate wobble call summit you can have a sfi one tommarrow for a extra 20.00.

01-04-2007, 04:51 PM	#11
68CHEBY Registered User Join Date: Dec 2006 Location: Louisville, KY Posts: 39	Re: Flexplate wobble Most of the heavy duty units are a lot thicker in the center, on the outer ring is welded on a whole lot better

01-04-2007, 05:36 PM	#12
TraderJon Registered User Join Date: Dec 2005 Location: League City,Texas Posts: 66	Re: Flexplate wobble Not to steal a thread,but you got me wondering now ? I just installed the rat motor & turbo 350 last night in the 67, I didnt pull the pilot bushing out of the back of the crank,motor had a 4 speed attached to it when i bought it,,,DID I mess up by not pulling the pilot bushing? Thanks JFd Last edited by TraderJon; 01-04-2007 at 05:43 PM. Reason: spelling

01-07-2007, 08:23 PM	#13
68CHEBY Registered User Join Date: Dec 2006 Location: Louisville, KY Posts: 39	Re: Flexplate wobble The pilot bushing shouldn't effect anything, the convertor should still be able to fit in the crank with no interference.

04-02-2008, 05:48 AM	#14
Blue'72 Skinned knuckles Join Date: Oct 2006 Location: Longview, Washington Posts: 1,126	Re: Flexplate wobble I'm going to resurrect an old thread.. Before asking my question, I decided to do a search. Ok, to save time, skip this paragraph and go to the next. I'm doing a frame off on my truck and do NOT want to have to come back and revisit anything after it's put back together. With all the problems I've had in the past and problems I've heard about with starters, I'm taking extra time making sure this new starter and flexplate are correct. I'm going from a 4 speed to auto, so I had to buy a new flexplate and starter. I adjusted the starter and then hooked it up to battery power so I could make sure it sounded ok. I noticed the flexplate is really wobbly. So, what's the verdict? Will a wobbly flexplate cause any problems, or will it straighten out once the torque converter is hooked up and there will be no problems? I will spend the money on a good one if you think I should, but I really don't want to spend any more money than I need to. __________________ '72 C-10 longbox soon to be short step! '72 Chevelle (sold in January) '07 Sebring '01 Ranger (I've gotta long commute..) If you try to fail, and succeed, which have you done? My build thread - http://67-72chevytrucks.com/vboard/s...d.php?t=276904



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