Dual Flex Plate or Single Flex Plate?

[scottr126]

Im lookin to get some opinions from fellow members with high hp automatic dsm's. Have any of you had any troubles with torque converter to flex plate bolts coming loose? There seems to be mixed opinions on how many flex plates to run and how to keep bolts in them.. Has anyone every actually broken a single flex plate to make them want to run 2 stacked?

I personally ran 2 stacked on my 2g with a 6 bolt in it. I used stock bolts and tack welded each bolt and never had a problem.

I now have a 1g transmission car and am trying to go with the same setup but am having troubles keeping the bolts from coming loose.



-Scott

 

[Jason's TSI]

I am running two stacked now, not welded, with some torque converter bolts from advance with alot of red locktite. No problems in the last 4 track visits. I was only having problems with the single plate with the car was missing or running rough under boost, then the bolts always wanted to come loose and crack the plate.

 

[scottr126]

Bolts from advance auto parts? Do you have a part number or size? I was going to start lookin for some arp bolts but if you have some that already work I would give those a try.

Scott

I am running two stacked now, not welded, with some torque converter bolts from advance with alot of red locktite. No problems in the last 4 track visits. I was only having problems with the single plate with the car was missing or running rough under boost, then the bolts always wanted to come loose and crack the plate.

 

[Jason's TSI]

The converter I'm running uses GM torque converter bolts, not stock mitsu bolts. So it depends on what lugs are welded to your converter as too what bolts you can use. Any high grade steel bolt in the correct thread pitch should work well.

 

[scottr126]

Oh I see.. yah the mitsu uses M10x1.25.. ive got some from ARP im probably going to get here and try out. Thanks.

Scott

The converter I'm running uses GM torque converter bolts, not stock mitsu bolts. So it depends on what lugs are welded to your converter as too what bolts you can use. Any high grade steel bolt in the correct thread pitch should work well.

 

[Jason's TSI]

Any reason you switched to a 1g trans?

 

[scottr126]

I built a new car. 94 AWD Mirage.. a 1g trans fits in there better. From what I have heard the 1g and 2g transmissions are the same internally.

Scott

Any reason you switched to a 1g trans?

 

[Jason's TSI]

yeah I thought they were the same, just curious.

 

[kiggly]

I'm using grade 12.9 allen bolts, M10x1.25 with red high temp loctite and 55ft-lbs.

Kevin

 

[scottr126]

Double flex plate im guessing? And what length allen bolts?

Scott

I'm using grade 12.9 allen bolts, M10x1.25 with red high temp loctite and 55ft-lbs.

Kevin

 

[kiggly]

Double flexplate, I cut longer allen bolts to length. I think they started at 20mm long, fully threaded.

 

[Rick539]

So the way I understand is you are using 2 stock flex plates stacked. How about on a 2G to 6 bolt. Since you are using the adapter, do you need to get another flexplate with it?

 

[4SFED4]

I run a single flex plate and tack weld the bolts.
I replace the flex plate and bolts every time I pull the trans or motor.
I never had a problem with the flex plate itself breaking, but I have ripped the threads out of the torque converter a few times.

My question is when someone is going to come out with a SFI rated flex plate and shielding system for a DSM?
I am in the process of doing all the necessary updates to my chassis and getting a NHRA license so I can run Pro 4 cyl next year. I don't want to get booted after spending the time and money to be legal.

 

[scottr126]

From what I have heard if there is no SFI whatever it be then they cannot require you to have it.

Scott

I run a single flex plate and tack weld the bolts.
I replace the flex plate and bolts every time I pull the trans or motor.
I never had a problem with the flex plate itself breaking, but I have ripped the threads out of the torque converter a few times.

My question is when someone is going to come out with a SFI rated flex plate and shielding system for a DSM?
I am in the process of doing all the necessary updates to my chassis and getting a NHRA license so I can run Pro 4 cyl next year. I don't want to get booted after spending the time and money to be legal.

 

[HighPSI TSi Guy]

I run a single flex plate and tack weld the bolts.
I replace the flex plate and bolts every time I pull the trans or motor.
I never had a problem with the flex plate itself breaking, but I have ripped the threads out of the torque converter a few times.

My question is when someone is going to come out with a SFI rated flex plate and shielding system for a DSM?
I am in the process of doing all the necessary updates to my chassis and getting a NHRA license so I can run Pro 4 cyl next year. I don't want to get booted after spending the time and money to be legal.

I agree this is really something that needs to be done. I think there's enough people needing one if we could even just do some sort of small group buy on it, it would work. I just finished converting my car to auto and this is the only thing that worries me. I set mine up with the double flexplate setup. We'll see how she does like that.

 

[dsmmack]

Question on the dual flexplate setup, I'm in the process of converting my car from 5spd to Auto. Its been ages since I've worked on an auto DSM. (used to own one at one point but never had the flexplate off, just the trans out to fix a broken band in the trans and put in a shift kit years ago)

I bought the whole complete auto trans setup from a guy, On the stocker there is a flat spacer that goes between the flexplate and the crank flange correct? I'm assuming this gets ditched and just stack the 2nd flexplate in there and the flexplate to converter location relationship is not altered and still maintains the correct location?
From the looks of the flexplate I have it looks that way from the resulting bolt marks left on it. (that is the spacer goes between the crank and the flexplate) I lent out my service manual to a buddy and don't have it back yet to reference.

Thanks.

 

[scottr126]

When I use 2 flexplates I just use them and no spacers, it works out well and it keeps the clearances for the most part correct, the only thing you may have problems with is the flexplate closest to the engine may be real close to the main seal housing/oil pan but it shouldnt rub.

 

[dsmmack]

When I use 2 flexplates I just use them and no spacers, it works out well and it keeps the clearances for the most part correct, the only thing you may have problems with is the flexplate closest to the engine may be real close to the main seal housing/oil pan but it shouldnt rub.

Perfect, I figured this is all that was needed, But just wanted to make sure. Thanks.

 

[420a-t]

Stupid question, but why are you guys using 2 flexplates? What's the advantage? Reason I'm asking is because I purchased a tranny built by IPT and this is going to be my first auto tranny replacement. Thanks

 

[Bender]

When using a high stall torque converter with an engine that is putting out a lot of ft lbs of torque, the stock flexplate holes become elongated by the instant jerking motion. Dual flexplates distribute the force to 8 points, instead of 4.

 

[420a-t]

Makes sense. Thanks for the info. So, around what whp or e.t. should one start to look at using two flexplates instead of one?

 

[Car Cannibal]

Kiggly, are you running two of your flexplates??

I am surprised no one has sent a shop the dual flexplates and made one large one that will take the abuse these cars are now putting out?? I know two shops that would do this if it would make sense to go this route.

I guess it's probably cheaper to just run two stockers and it seems the tracks are cool with it as we have two 9 second DSM's in this thread doing it.

 

[Bender]

I'm not sure whp is going to be much of a factor here. Being turbocharged cars, dsm's make their horsepower upper end. If they were supercharged, it might be a different story. The point is, on turbo cars the power is laid down at higher rpms, where this jerking on the flexplate and torque converter isn't happening. What determines it is ft lbs of torque and at what rpms you are launching at. A car launching at 4500 rpms at 20lbs of boost and making approximately 215 ft lbs of torque is going to have less stress on his flexplate off the line than someone launching at 6000 rpms at 30 lbs of boost with 400ft lbs of torque. So really to be safe, I would say anything faster than high 10's and over 400 ft lbs of torque. Maybe less to be slower to be real careful, but I think going faster with a single flexplate is doable also.