Auto Flexi plate / fly wheel

Clutch, Gearbox, Overdrive, Propshaft, Differential, Drive Shafts, Hubs.
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Auto Flexi plate / fly wheel

#1 Post by dolomitejohn » Wed Jul 04, 2018 9:06 am

Hi All,

Does any one know if the Auto Flex plate (Fly wheel) on a 2500 Auto has a tendency to break / shatter at high mileages ? I ask as I looking at an Auto and am remembering back to my Dolomite 1500 HL Auto which broke its Flexi plate on the M6 at 80 MPH. Had lasted 128000 miles though.... Bizarrely it still drove as the section of plate still attached to the crank was jamming in the section of plate still attached to the torque convertor. Nice noises mind.........

Also, any one know the engine speed of a 2500 S Auto at 70 MPH ?

Thanks All.


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Re: Auto Flexi plate / fly wheel

#2 Post by johnnydog » Wed Jul 04, 2018 10:49 am

The flexi plate on the auto version of the 2000/2500 has had a tendency to crack around the four mounting holes purely because the auto flexi plate is a lot thinner construction than the manual flywheel, and the torque required to turn the engine over over time fractures the weakest point. I wouldn't say it is mileage related, although the more use a car has had, then components, as with any car, will wear out with age and the type of use (regular stop starting or long distance use). Given that our Triumphs tend to have more of a limited use, and are now over 40 years old, then high mileage isn't really relevant in my opinion.
I have two autos, one a 2000 and one a 2.5 and there is no signs of flexi plate issues.
I do believe Chris Witor supplies a reinforced flexi plate to prevent cracking at the weak mounting point.
An auto sounds a lot tinnier when they are turning over on the starter than a manual because of the thinner metal of the flexi plate. When there is an issue of cracking, you will hear the horrible noise it will make when the plate is flexing on the starter.
Without looking up the data, from memory, at 70mph, auto 2500's are doing about 3500rpm, whereas the manual 2500's with the 28% reduction overdrive engaged are doing about 2700 rpm. That is assuming of course the correct diff of 3.45:1 is fitted and the tyres are the correct size. Later 2500 TC's had 185x13 fitted like PI's but as they are now difficult to source other sizes are often used. 'S' models originally had 175x14 tyres fitted which (as the sales brochure quoted!) provided slightly higher overall gear ratios.
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1967 Mk1 2000 in Gunmetal Grey
1969 Mk1 2000 in Royal Blue
1970 Mk2 2000 in Valencia Blue
1972 Mk2 2.5 PI in Triumph White
1973 Mk2 2.5 PI in Sienna Brown
1976 Mk2 2500S in Carmine Red

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