Some of you might remember my broken flexplate issues, and it's back to haunt me again! Here goes, I have a 1964 A-100 van with a 225 that seams to break new flaexplates every 4 months. The issue started about a year after I bought the van. I pulled the trans. out for a rebuild by a very reputable Trans. guy. When I pulled the trans, what appeared like an old, original flexplate was in great shape, so when I put it back together with a new torque converter, it went right back into the van. Everything was great, but in about 4 mos. the flexplate was cracked. I replaced it, and when everything was apart, I checked all clearances, etc. everything looked good, so a new plate went in & all was fine until that plate cracked (#2). the same thing, broken at a few of the corners accross the bolt holes for the TC. when I took it apart that time, I took the trans back to the guy that rebuilt it for me who went through it again. the trans tested out just fine, but I suspected the tc, & put a new one into it. and a new flexplate. Again, after about 4 mos. That plate was cracked (#3). this time, I double checked all clearances, end floats, etc. and it seemed the machined space for the nose of the tc in the adapter at the end of the crank was a little too close (seemed maybe a little shallow) I machined the adapter a little deeper to allow plenty of room for the nose of the tc. and put it all back together with a new flexplate (#4). Now once again, the flexplate is broken on 3 of the 4 holes that hold it to the tc. I'm getting desperate to fix whatever is busting these things! ANY ideas would be appreciated!

did you follow all suggestions offered in the last thread you posted? seems lou had a solid grasp of what was wrong...

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I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

I will trade you a slant six 727 trans and a flexplate (!) for the small-block tranny adapter setup in your van. It needs a rebuild and a torque converter, but it would bolt right up to your transmission and eliminate any potential problems of misalignment between the motor and transmission. You could use your existing 727 torque converter and swp guts from your smallblock case to the slant six case.

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Casually looking for a Clifford hyperpak intake for cheap.

Yes, by machining the adapter, there was plenty of space for the depth of the nose of the converter. thus I didn't need to use his suggestion of grinding down the nose of the tc or using washers between the adapter & the flexplate. Feeling like I resolved the issue, I did however use a standard slant six flexplate rather than going with a 8cyl one. I wanted to try to solve & fix whatever is causing this rather than just beef up the flexplate as a sort of bandaid fix. Don't know what to do now, though...

Like I say, I will trade you the slant six specific 727 tranny AND a good flexplate for the adapter and associated hardware. Shipping might be expensive though.

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Casually looking for a Clifford hyperpak intake for cheap.

To me it appears the case is not concentric with the crankshaft of the newer engine. The only way to know is to take the empty trans case and bolt it up to the engine with a dial indicator on the crank and check the runout. Chances are good you'll need offset dowel pins to correct the transmission to engine alignment. Are the factory dowel pins in place?

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Joshua

The (2) factory dowel pins are in place and are in very good shape. everything seems right. I know the motor is slightly newer than the trans which appears to be original to the van (1964) and an old receipt that came with the van when I bought it looks like the motor was an "upgrade" that looks like it was done sometime in the '70's. The thing that stumps me is that when I took the trans. out the first time, the old flexplate was in good shape. That is why I started thinking that the problem popped up during the trans. rebuild. the only new thing at that time though was the new torque conv. but that was replaced later by one from a different manufacturer as I said. VERY frustrating!!

Make very sure that the adapter plate or the spacer on the crank have not cocked. They have to be mated perfectly or the flexplate will wobble and crack.

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Official Cookie and Mater Tormentor.

If the case was not concentric with the crank, wouldn't that show up when I bolt the trans up to the motor? When the flexplate is bolted to the crank, and the trans is bolted in place, all the bolt holes (flexplate to converter) have always lined right up. Could the eccentricity be so small that the bolt holes still line up? Again, I keep thinking that this trans and motor have been together for a long time before I got the van and the flexplate that was in there when I took the trans out for the first time was in good shape. So doesn't it seem like the current dowel pin setup, etc should be fine & that the motor and trans should be compatible?

I don’t know much about transmissions but one thing is almost certain - something isn’t concentric.


But does it bend the flexplate when you tighten the bolts?

Can you check if the flexplate sits flat against the torque converter before it’s bolted together? If not, I’d check that the rear of the crank is machined true and that the pump isn’t holding the converter crooked. That seems to be the only thing you haven’t changed since the rebuild.

Danny

Wait a minute, Since my trans is actually an 8 cyl. trans. and the adapter that mounts on the crank probably duplicates an 8cyl, to accomodate the 8cyl. trans., doesn't that mean that everything behind that crank adapter thinks it's an 8 cyl? wouldn't that mean that the torque converter should be for an 8cyl?? And maybe the flexplate too?? Is it possible that the guy who did my trans. rebuild, put in a converter and flexplate for a slant six, & that I need one for an 8cyl?? When bolting the flexplate to the converter, the converter pulled up flat to the flexplate by hand, & all hole line up nicely. The bolts do not stress & bend the flexplate at install.

At this point, I think a bunch of detailed pictures of each part you are talking about would be very helpful.

As far as I know, the transmission and torque converter are straight v-8 material and design. In 64 there was no slant six 727, so Mopar just took the standard V-8 transmission and made an adapter. The flexplate should be a six cylinder flex plate though. The important parts are that the flex plate bolt securely to the crank and the flex plate matches the bolt holes on the torque converter.

It sounds like something might be hitting the flex plate, causing damage. Are there any protrusions on the torque converter? Is something protruding fomr the block or the adapter which is rubbing or hitting the flex plate as it turns? The repaeated breaking at the very ends of the flex plate makes me think it is hitting something.

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Casually looking for a Clifford hyperpak intake for cheap.

I had a misaligned Slant 6/V8 trans adapter plate in my '68 with A500 trans, and was cracking flexplates just as you describe. I switched to another plate and the problem went away.

Best way is to pull the trans and follow factory procedures for at least making sure the plate is concentric with the crank, and the best would be to pull guts out of the trans and make sure that is concentric with the crank.

I'm pretty sure you have a crank/trans input concentricity problem.

Another way I'm about to try to eliminate a small residual crank-speed vibration is to use some "quick release" Mr. Gasket 0.014" offset dowels and rotate them in 60 or 90 degree increments, observe the vibration, and find the best orientation.

Lou

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Home of Slant6-powered fun machines since 1988

Thanks to everybody for the help in chasing down this issue. I can't find any mention of the factory procedures for making sure the plate is concentric with the crank in my service manual. I actually can't find mention of the adapter plate at all even though I'm pretty sure my service manual is for my year van (1964). If anyone has the factory procedures and can let me know what they are, that would be a great help. The trans. is still in my van, so I will post again soon when I take it out. Thanks again!

Tom

The factory procedure would involve pulling the guts out of your trans, bolting trans/plate/engine together, and using dial indicator to look for concentricity. Plate alone would take a little ingenuity to figure out how to do this since there is no well machined hole in the center of it.

I don't see how if you rebuilt the trans that came with the engine/plate you could be having offset issues, UNLESS your dowels got goofed up or there is some piece of schmutz interfering with a good seat between engine/plate or plate/trans.

You might try getting a spare A727 V8 trans and gutting it to check for alignment, instead of using yours.

Or, you can try the dowel trial and error trick I described above but haven't tried yet. Here is what I bought, figuring I can rotate them with the engine/trans still connected, or maybe only slightly parted.

http://www.jegs.com/i/Lakewood/620/15954/10002/-1

1) Check for vibration over a range of RPMs (new flexplate). Remember how this feels, or check with microphone and oscilloscope?

2) Rotate dowels 90 deg, repeat vibration check, and repeat as necessary to get lowest vibration.

I figure this will take me about a whole day of futzing to get it right, and haven't done it yet since vibe isn't bad on my car.

Cheers,

Lou

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Home of Slant6-powered fun machines since 1988