FMF/C6 Flexplate HELP !!!

FMF/C6 Flexplate HELP !!!

Joined: July 23rd, 2009, 8:23 pm

July 23rd, 2009, 8:32 pm #1

Hello All,
This is my first post here and I am in desperate need of info. Im building a 69 Vert Mustang (Restomod) with a 351 Clevor (Windsor Block with Cleveland heads. The engine was built by a local machine shop with a very good rep. The trans is an FMX that I had a local Trans shop rebuild, good rep also. When the machine shop built the engine they put on a new flexplate. The motor and trans went together no problem and it fired up right away. However, during the 20 min run in for the engine the trans started puking fluid. Apparently the machine shop put on a flexplate that was 1/4" deeper than the original one (Maybe a C6 plate ????) and the tranny guys are saying that it pushed the pump back which blew up the pump gears and made a huge mess. Now the trans has to be rebuilt AGAIN at a cost !!
Does this sound correct ??? Are there different flexplate 'depths' for the FMX, C4 and C6 ???

Thanks !!
Last edited by sixninevert on July 23rd, 2009, 8:43 pm, edited 1 time in total.
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Joined: January 1st, 2004, 2:15 am

July 23rd, 2009, 10:34 pm #2

No...I interchange transmissions on my 70 (FMX->AOD->C6) all with the same flexplate so far. But, to be sure, remove the flexplate and measure how deep it is so we can double-check.
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Chevy-Lover
Chevy-Lover

July 24th, 2009, 1:14 am #3

If they didn't get the input shaft engaged properly in the pump and torque convertor this would be real bad stuff....After the transmission is bolted up to the engine block there should be a small amount of play between the flexplate and torque converter before they are bolted together. It is not much maybe 1/8 inch but if there is none you got big problems. Many a transmission has been ruined by this lack of attention to detail.....
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Chevy-Lover
Chevy-Lover

July 24th, 2009, 1:23 am #4

Also if the torque convertor does not seat properly in the crankshaft recess that could also cause problems.
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Joined: July 23rd, 2009, 8:23 pm

July 28th, 2009, 2:46 pm #5

Well according to the tranas shop there is a difference in the 'depth' of some SB Ford flexplates. Mostly for the C6 trans. The difference is about a 1/4". If this particular plate is used on an FMX trany it can/will push the pump against the housing. Causing catastophic issues !!...and a lighter wallet !
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Joined: January 1st, 2004, 2:15 am

July 28th, 2009, 3:57 pm #6

Hmmm...but when you look at the flexplates you won't see the 1/4". Have done all the transmissions and can't find a difference (yet). I smell bad info coming from the shop...
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Chevy-Lover
Chevy-Lover

July 28th, 2009, 6:36 pm #7

Well according to the tranas shop there is a difference in the 'depth' of some SB Ford flexplates. Mostly for the C6 trans. The difference is about a 1/4". If this particular plate is used on an FMX trany it can/will push the pump against the housing. Causing catastophic issues !!...and a lighter wallet !
I believe your shop speaks with forked tongue....prob trying to blame something for their screw-up...JMHO...
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Chevy-Lover
Chevy-Lover

July 28th, 2009, 6:38 pm #8

I have seen where some knuckle heads put the flexplate on backwards...lol...
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Chevy-Lover
Chevy-Lover

July 28th, 2009, 7:49 pm #9

One more thing...I'm not sure on the your 351 but some blocks have a "spacer" plate that goes between the block and the bell...if it is left off then it will make the trans bind and prevent proper depth engagement....
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Dave Shoe
Dave Shoe

July 28th, 2009, 10:29 pm #10

There are some documented 400M offset issues regarding flexplates. I don't know whether it applies in this case or not. Note that the six "spokes" of the flexplate of a 428FE engine are not universal identifiers (there are plenty of exceptions nowadays), so it is possible they are no longer necessarily universal identifiers in this 400M application, though they would have been universal at the time of the TSB release.



Note that the concept of the six spokes "seems" to have originated in the fancy 2-piece flexplate of the 1966 428FE which "seems" to have been designed to help give the luxury Galaxie a Rolls Royce ride quality (to match the advertising of the day), and "seems" to have been carried over to the more cost-effective one piece flexplate of the 1967-later 428FE engine. It "seems" the spokes eventually translated to other Fords, and seem intended to isolate some crankshaft vibration from the drivetrain. Obviously, this is just baseless opinion of mine, founded on my rudimentary observation of the spoke evolution, but I like the notion.

Hope this helps.

Shoe.
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