Hope some of ya can take a brake from fighting on this forum and answer a mechanical question: just as the title says - what's the difference? They are similar it seems - one is heavier than the other.... is it the automatic vs the manual trans that makes the difference?

Thx,
James

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1987 Mercedes 300SDL; SOLD
1985 Mercedes 300D; SOLD
2006 Honda Pilot - wife's ride; 122K;
1995 Toyota Land Cruiser - 3X locked; 182K

Flywheel is for a manual trans, flexplate is for an auto.

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1984 300TD 1981 240D

A flywheel bolts to the crankshaft and is typically used with a clutch with a manual transmission. It serves as the friction surface against one side of the clutch disc. It has a good bit of mass to store energy to keep the engine turning between pulses at idle.

A flexplate is very thin and also bolts to the crankshaft. It serves to mount the very heavy auto trans torque converter. The weight of the torque converter provides the mass as described above.

Both of them have a ring gear for engagement of the starter.

Hope this helps
Larry

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2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

Yes - thanks very much... Are the flex plate and flywheel specific in weight to an engine or are they fairly generic and interchangable (within reason) among different vehicles?

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1987 Mercedes 300SDL; SOLD
1985 Mercedes 300D; SOLD
2006 Honda Pilot - wife's ride; 122K;
1995 Toyota Land Cruiser - 3X locked; 182K

Different in weight. Some are balanced together with the specific crankshaft in the engine so are not simply interchangeable. Flex plates are more likely to be interchangeable I think.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Generally Kerry is correct. This, again generally, is because a flexplate has very little weight to begin with.

Engines are either internally balanced with crankshaft counterweights and such, or externally balanced where specifically positioned and specific size weights are put on the harmonic balancer and flywheel. So, obviously, an externally balanced engine will sometimes have a balancing weight on the flexplate or maybe in some engines the torque converter.

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2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

Some manual transmission cars have flex plates too, like many neons, both automatic and manual engines were assembled with a flexplate, than a clutch or torque converter bolted to it depending on what car it went in.