Flexplate cracking!

SVXRide · #1 06-23-2006, 01:47 PM

Having just starting hearing the very familiar sounds of a cracked flexplate after less than 1k miles after replacing the "donut" flexplate that was in BillStock v3.5, I was wondering what other's experiences have been with the 4HEAT/EG33 flexplate. Is there a certain number of miles after which they will tend to crack? Are there any known contributors to the plate cracking (too much longitudinal play in the engine crank? slop in the trans? ) I'm seriously considering having a "beefed up" version welded together

-Bill (kicking himself for not installing a brand new flexplate....)

Chiketkd · #2 06-23-2006, 02:27 PM

Bill, sounds like dumb luck (or ill-luck) in this case especially since you installed a used flexplate as a replacement. Even though the SVX flexplate isn't the beefiest thing in the world, it has still held up to the power of LAN's and svxfiles' s/c SVXi!

From what I've seen, they tend to go out between 130-150K miles on several SVXs.

SVXRide · #3 06-23-2006, 02:41 PM

Quote:

Originally Posted by Chiketkd

Bill, sounds like dumb luck (or ill-luck) in this case especially since you installed a used flexplate as a replacement. Even though the SVX flexplate isn't the beefiest thing in the world, it has still held up to the power of LAN's and svxfiles' s/c SVXi!

From what I've seen, they tend to go out between 130-150K miles on several SVXs.

Chike,
compared to the plates I'm used to behind sb chevy engines, our flexplate is a piece of aluminum foil

. Adding the through holes only makes matters worse. I'm guessing the Subaru engineers were really looking to smooth out the driveline shock when the trans shifts, at the expense of life span under "non-stock" conditions. This is why I started this thread. I'm guessing any modification that makes the trans shift "harder" (small car kit, Tom K's resistor mod, etc.) will inherently put more load on the flexplate. I don't think LAN's car has had anything done to the way it shifts (but then I could be wrong).
-Bill

Earthworm · #4 06-23-2006, 02:42 PM

Think it's possible to stack 2 of them together or would there be clearance issues?

cdigerlando · #5 06-23-2006, 02:49 PM

Out of curiosity, where is it cracking?

SVXRide · #6 06-23-2006, 08:20 PM

Quote:

Originally Posted by cdigerlando

Out of curiosity, where is it cracking?

Chuck,
almost immediately below the "washer" plate that goes over the flexplate and the bolt go through to attach the entire assembly to the end of the crank. While not a perfect circular crack, it's very close to one.
-Bill

SVXRide · #7 06-23-2006, 02:50 PM

Quote:

Originally Posted by Earthworm

Think it's possible to stack 2 of them together or would there be clearance issues?

Tom K and I were discussing welding/riveting on a "washer" that has a diameter of at least 2x the current one (since the "knife edge" is where the flexplate flexes against the current "washer")

-Bill

Beav · #8 06-23-2006, 04:12 PM

Absolute #1 cause of flexplate cracking is the lack of alignment dowels between the block and transmission. The bolts don't align the two together, the dowels do. When the dowels are missing the crankshaft and torque convertor are not spinning on the same axis.

#2 'Hanging' the trans from the flexplate during install/remoaval. This bends the flexplate and causes wobble.

#3 Distorted convertor face from excessive lock-up clutch pressure or poorly rebuilt convertor (off-center stub.)

SVXRide · #9 06-23-2006, 08:25 PM

Quote:

Originally Posted by Beav

Absolute #1 cause of flexplate cracking is the lack of alignment dowels between the block and transmission. The bolts don't align the two together, the dowels do. When the dowels are missing the crankshaft and torque convertor are not spinning on the same axis.

#2 'Hanging' the trans from the flexplate during install/remoaval. This bends the flexplate and causes wobble.

#3 Distorted convertor face from excessive lock-up clutch pressure or poorly rebuilt convertor (off-center stub.)

Beav,
Damn, damn, damn!

Count my car as another victim of #1. One of the alignment dowels was actually missing when we pulled the trans, so I'm guessing only having one pin contributed to the first plate cracking. Figured the 4 bolts handled the alignment, so we didn't dig up another dowel when we installed the latest plate....crap!

Thanks so much for your insight on this...won't make this mistake again!

-Bill