GrandSportC3

That may be a stupid question but I would like to know exactly what the difference between a flywheel and a flexplate is.
It is my understanding that a flexplate is used in combination with automatic transmission and a flywheel is used for a manual transmission. Is this correct?
Why are flywheels much more expensive than flexpates?

thanks

Olivier

bbeck

My understanding was always that a flexplate is for an Automatic tranny, and a flywheel is for a Manual. But, when looking to buy people don't always use the same terminology, so be sure to check.

fauxrs

Flywheels are for manual transmissions they're weight can vary greatly depending on the material - billet steel, cast iron, aluminum.

Flexplates are used exclusively for automatics and are generally a piece of stamped steel with a ring gear welded on.

Like all car parts quality varies widely.

Price is obvious, which is cheaper , a 35 pound slab of billet steel or a stampied piece of 10 gauge galvanneal with a ring gear weldedonto its curcumference.

GrandSportC3

>>Flywheels are for manual transmissions they're weight can vary greatly
>>depending on the material - billet steel, cast iron, aluminum.
>>Flexplates are used exclusively for automatics and are generally a piece of
>>stamped steel with a ring gear welded on.
>>
>>Like all car parts quality varies widely.
>>
>>Price is obvious, which is cheaper , a 35 pound slab of billet steel or a
>>stampied piece of 10 gauge galvanneal with a ring gear weldedonto its
>>curcumference.

Thanks for the information! However - I have one more question:

When I purchased a "external balanced" engine for my 69 (sold) I had to use another flexplate because the engine was a 383 instead of a 350.
Is this the same way for flywheels or can I use my current flywheel when purchasing a engine with a different size crank (externally balanced)?

Thanks

Olivier

vettfixr

350 engines are internally balanced ( 0 balance) while 383 engines are externally balanced (offset or out of balance). I'm not sure if I'm using the right terminology here but a 350 engine requires a flywheel or flexplate that is in perfect balance (0) while a 383 engine, due to the use of a 400 crankshaft must have a flywheel or flexplate that is offset balanced by a certain number of ounces. I believe the reason for this is because the larger pistons in a 400 engine would require crankshaft counterweights that are too big to be accomodated by the engine case. The flywheel or flexplate for a 383 or 400 engine typically has a weight welded to it to throw it out of balance the correct number of ounces. Like everything else there are exceptions to the rule. You can get a 383 or 400 assembly that is internally balanced through the use of heavy metal (Mallory metal) and then use a zero balance flywheel or flexplate. Flywheels and flexplates also come in different sizes and different tooth counts (153 vs 168) that require different starter nosepieces. This just keeps life interesting. :)


[Modified by vettfixr, 9:38 AM 5/1/2002]

fauxrs

[QUOTE
When I purchased a "external balanced" engine for my 69 (sold) I had to use another flexplate because the engine was a 383 instead of a 350.
Is this the same way for flywheels or can I use my current flywheel when purchasing a engine with a different size crank (externally balanced)?

Thanks

Olivier
[/QUOTE]

On any externally balanced engine you will need the correct balancing device at either end of the crank - since your 383 is based on a 400 crank - externally balanced - you will need a harmonic balancer from a 400 and a flywheel or flexplate from a 400.

Internally balance motors use neutral balanced componants so a 350 flywheel/flexplate should NEVER be used on a 400 crank. Also know that the newer 350s, I dont remember where but starting perhaps with the LT1 in the c4 vette are also externally balanced.