Destroyed another flexplate....

[quagmire]

A year ago I had to replace the torque converter and flexplate due to the bolts coming loose and tearing the parts up.  I was driving to work in my car earlier this week when I heard that rattle noise start up again.  It only does it when it gets good and hot.  Upon getting home and inspecting it I found all 4 mounting ears cracked where the bolt holes were.  The bolts were not loose. I really hope the cheapo Advance Auto Parts flexplate I installed was just weak, but it was identical to my SFI one I originally used.  Crank end play is ok, dowels are in the block, and the PTC converter seated perfectly.  Anyone else have this problem before? 

So the trans is coming out again, I think I will tear it down and make sure everything else is ok.  My 2-3 shift is brutal while the 1-2 is nonexistent, I want to install a stock VB and modify it with the transgo kit instead of the CRT one it has now.  If anyone has a complete stock valve body let me know, I need to get one fast since I'll be on vacation in a week.  So much for cruising and relaxing. 

[426HEMI]

Just make sure that there is not anything in between the trans and engine like dirt or grease on the mating surface could be an alignment problem.  is the bushing in the front pump worn?  could be the converter moving also.  Just trying to help. 

[tactransman]

There has been some posts on Moparts about the flex plates cracking and the converter bolts coming loose and such. I never seen a reason for them.

I can come up with a VB if you need one. What year is your 904?

[quagmire]

I think this time around I'll try the B&M one, I heard it is pretty beefy.  I'll definitely buy a valve body from you, I don't have time with work to scrounge around any junkyards to find one.  Once I get home I'll check that case number and PM you, thanks!

[tactransman]

This one is a good one,it is thicker,does not hve the holes by the converter bolt holes and is SFI approved. (does your converter use 7/16 thread bolts?)

http://summitracing.com/parts/DCC-4529751AB/

[Chryco Psycho]

if it was a 4 spd I would make sure the belhousing is centered properly , not sure how to accomplish this on an automatic though

[quagmire]

Yeah, I'm not aware of any way to do that since the bellhousing is part of the case.  I don't even think they make an eleventy billion dollar Kent Moore special tool for it either for the autos, kinda stinks not knowing.

To tactransman:  My 904 converter does use the bigger 7/16 bolts, I'll give that one a try then.  I got my case number and will be PM'ing you here in a few once I decode it.

[Ck[FIN]]

I have used the B&M flexplate in my low and high horsepower engines. No problems so far. And it has holes for smaller or larger bolts.

[CUDA JAS]

Do you have the support braces between the block and the trans?

I lunched a couple of flex plates several years ago.  I reinstalled the braces and have not had a problem since. 

Just a thought.

[vinb]

Sounds like you may have a balance problem. I would send the convertor out and get the transmission checked and install a new flexplate.

I always used a 904 factory plate with the holes in it on my Stockers & my SuperStocker  making anywhere from 430 hp to 585 hp never had any problems...

Vin....

[quagmire]

I have the trans apart, it all checks out okay so far.  The converter has been changed since the last time around, and it is has no weights since my engine is balanced internally.  I do not have braces, someone tossed them before I owned the car.  I dont know, the Advance Auto Parts flexplate was only $17.........  Maybe it is cheaply made.  The first TCI brand SFI flexplate got trashed because the bolts on the old converter came loose and damaged the holes.  So in all fairness, I can't really blame that flexplate for failing.  I just want to be sure this won't happen again in the off chance their is another problem. 

[quagmire]

After measuring and checking the entire trans out, I did find that all of the front clutch steels have a small spot of heat scoring in one area.  The clutches all look fine, but every steel has this scoring in the same spot on the clutch stack almost like something is bent or high.  Everything checks out flat so far, and the clearance measured to .045".  That is tighter than spec, but I am running 5 clutches in the 4 clutch drum.  I'm not sure what the cause of that is, but I doubt it is coincidence since my car slams into reverse and 3rd gear and the front clutch is engaged in both of those gears.  I don't think it is related to the flexplate problem, but the harsh shift was another concern I had. 

Also, is there supposed to be a metal washer or race on top of the #3 thrust washer that goes between the input and output shafts?  My end play was in spec, but for some reason I remember there being two washers on the end of the input shaft of the LU 904 I tore down.  I only have one fiber washer.  I don't think anything fell out when I tore it down.

[quagmire]

 

Does anybody have any insight about these issues?  I'm thinking I may need to get the top pressure plate machined down .030" to bring my clearance to .075".  Maybe the front clutch is engaging too fast and/or dragging slightly after thermal expansion. 

[tactransman]

You need to have it at about .075. What is the thickness of the top snap ring?

[quagmire]

I believe it was a flat .077" when I measured it yesterday.  All of the clutches measured .061" and the steels were the normal .068" too.