This is quote from MOSS:
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[TD="class: MoreInfoItem, align: justify"]The 4 cylinder TRs were fitted with 3 different types of flywheels throughout production. The 3 basic types are as follows: 1.- Flywheel with shrink-on ring gear, originally fitted to TS50000, which goes with the early shrouded starter motor and spring-type clutch cover. 2.- Flywheel with bolt-on ring gear for later starter motor and spring-type clutch cover originally fitted to TR3A from TS500001, TR3B and all TR4s. 3.- Flywheel with bolt-on ring gear and 8 1/2" diaphragm clutch, originally fitted to all TR4A. None are available, but due to the propensity of car owners to mix and match, you could have any combination fitted to your TR.
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