Aftermarket flexplates?

JasonMiller94SC

Registered User
I've been running a Mark VIII converter and flexplate in my car for about 3 years now and the car runs great. That was untill I started hearing a knocking noise comming from the bell housing of my car. The trany had been rebuild but I've since put about 65,000 hard miles on it so I figured maybe something in there broke.

After talking it over with my friend Jay we decided to make sure the toque converter bolts had not backed off. We put it on the ramps and snugged each one down and Ta Da! No more noise. I drove the car home with a big simle thinking I had fixed the problem.

The next day and about 40 miles later the noise was back.

The only other think I could think of to check was that maybe one of the bolts holding the flexplate to the crank had backed out.
I bought a new flexplate and took my car back to Jay's garage so we could pull the tranny out.

As soon as we had the tranny back I was able to see the problem.

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A slight tap with a rubber mallet and:
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My question is, what would cause this? All of the bolts in the center were very tight.
I got this part from someone who had used it for about a year and he got it new. I'm wondering if he got it from somewhere else besides ford. You can see the new one in the picture looks like it is made different and the new one I got directly from the ford dealership and it has the ford oval and part number stamped on it. The old one has no such markings.
The new one also feels like it weighs more but I didn't actualy weigh them.

Has anyone seen this before?

On a side note when I took the car to Rockingham dragway this past Febuary on a 800 mile roadtrip for my girlfrinds birthday I heard it making a sight knocking sound that I passed off as being a loose heat shield on my cat. I now know it was the flex plate. Well with no bottle and on street tires with the flexplate rattling away the car still ran 13.3's all day. I'm hoping it might run a little better now. :)
 
after market parts are made cheep,and in cases like yours your lucky it did not spin and cause more damage.looks like it was not tourked to spects,just bolts put on with air gun,to tight.
 
I don't think an air gun was used the last time I had the motor out.
It sure as heck wasn't this time. No way to get an air gun up under there with the tranny only rolled back 8 inches.
 
I have done this 3 times on a Tempo. The engine had been rebuilt and the original had 160,xxx on it so I took it as it was just worn out. It had lasted about 3 months. The second 1 came from a 90,xxx mile junk yard car and lasted 1 month. The third 1 came from Ford and lasted all of 2 weeks. At that point I decided to look further into it. I contacted the rebuilder and they were no longer in business. I put a dial indicator on the flange of the crank and it had a very slight "wobble" to it. I think it was like .005 of something. I called around and was told that it was to much and that was causing the centers to wear like that. The bolts hold the center tight and the input shaft of the transmission keeps the torque converter from moving and it eventually fatigues the metal and eats itself just like that picture. You may want to put a dial on the crank flange and see what kind of runout you get. Maybe call some shops and see what is allowed.
 
Had the same part break 4 times within 3000 miles on a buick century...ended up being a problem with the transmission being out of allignment with the crank shaft. Factory defect in the bell housing was preventing the transmission for bolting up square with the block.

Do you still have the allignment dowels in place ?

David
 
Wouldn't an out-of-balance tc cause something like this? Was the trans mated firmly against the block...any of those bolts loose? You said you snugged down the tc bolts - did any seem loose at that time?

Flexplates flex...that's their job :) Cracked/busted out centers happen on many types of vehicles and often enough that they are A-listed suspects when someone thinks they have a rod knock... Having one fail over time is not exactly cause for alarm, but if you need to go back in for the same thing again soon, perhaps something else is knocking it out.

*Check out this TSB on 1999 F-Series trucks:
Date: 07/01/1999
Component Name: 061000 ENGINE AND ENGINE COOLING:ENGINE
NHTSA #: 6585
SUMMARY: SOME VEHICLES EQUIPPED WITH 7.3L DIT DIESEL ENGINES MAY DEVELOP A CRACKED FLEXPLATE. *TT


Have you checked for TSB's on your donor car?

Ken
 
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i did not mean you did it maby a previous owner,sorry if i offended you.

No offence taken. I like to hear any ideas.

I got the car from the previous owner when it only had 33,000 miles on it. My friends and I have done most of the work to it. Transmission was build about 6 years ago and 2 years ago Coy Millers shop built the motor.

When the torque converter bolts were tightned they were not exreemly loose but I think my friend was able to put a 1/4 or 1/2 turn on each one.
The tranny was mated up to the block firmly and none of thoes bolts were loose. The allignment dowels are still in place.

Like I said I've been driving on it for abou 3 years and I suppose maybe it was a cheap part not realy designied for a car that makes 450 ft lbs of torque. I'm hoping the Ford part will hold up better.
 
JasonMiller94SC>...been driving on it for about 3 years and I suppose maybe it was a cheap part not realy designied for a car that makes 450 ft lbs of torque. I'm hoping the Ford part will hold up better.

In that case, I'd consider it a $50.00 safety valve and count 3 years as a decent return on my investment. If the fp simply handed off abuse from high-torque race floggings, something more expensive might be next in line :)

Ken
 
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Maybe I'm in the same boat

I noticed I developed a simialr knock at idel to 1100rpms in neutral or on very light loada/speed while coasting. Been like that since september almost 4,500 miles ago. Seems to be near the rear oil pan/bell housing and resonates through the harmonic ballancer. Also gives vibration though slight from 2600-3500 rpms give or take some in neutral, as a cracked flexplate would be out of ballance? Its a 94 auto.
 
Most often a cracked flexplate is caused by a ballooned converter. The real solution is to get a converter that is rated for the RPM and power level you are at.
 
maybe that where mine is makeing noise was fine just put the good used tranny in it. i steped on it off the line and it's got this ticking/hamering right then. it was time it's been a 100 miles:rolleyes: runs fine no loss or power just hamers like h*** now. beter place to start looking than lifters/rods
 
Most often a cracked flexplate is caused by a ballooned converter. The real solution is to get a converter that is rated for the RPM and power level you are at.

Dave,
I put the Mark converter in because I was gonna spin the motor to 6,000 rpms and I figured the Mark one would handle that. Would the car drive different if the converter was ballooned? Right now with the new flexplate in the car drives great.
 
Did the flywheel bolts leave marks on the converter? If they did then that's your answer. Most if the time if the ballooning is not bad then there will be no symptoms. Better ask Alan Brown about it though as he's the converter expert. For 6000+rpm I'd recommend a better converter.

A hillbilly fix might be to put spacers behind the converter studs to give you a little more room but if the converter is ballooning then that's just a bandaide to a bigger problem. The reason the flexplate is cracking is because it's being forced to flex too much. A billet flexplate would stop the cracking but then you might wipe out your thrust bearing in the motor (you might anyway) so that's not the right way to fix the problem.
 
I didn't inspect the converter for any marks so I don't know if the bolts left any marks.

I've looked at getting a converter for the car but right now I'm trying to save money to buy a house so buying a $600 converter is out right now.
I figure the car is about a converter change from running 11's anyhow so when I get settled in a new place I'll save up for one.
 
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