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Cummins M11 Accessory Drive Question

May 28, 2024, 04:19:43 pm

Our 1995 U320 M 11 engine has a pulley on the accessory drive the powers the belt to the alternator and another pulley that powers the belt to the A/C compressor. I assume that these two pulleys rotate at twice the crankshaft speed—but I haven't been able to verify. Does anyone know for sure?

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Re: Cummins M11 Accessory Drive Question

Reply #1 – May 28, 2024, 04:36:28 pm

If it's not immediately important I can use my tach when I get home to tell you the answer.


Stewart Warner SW PORTABLE HAND Tachometer MEASURES ROTARY SPEEDS W/ CASE -...

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Re: Cummins M11 Accessory Drive Question

Reply #2 – May 28, 2024, 05:14:39 pm

These pulleys are not directly attached to the crankshaft. They are driven from the crankshaft by the gears in the accessory drive gearbox assembly. I haven't been able to find the details of the gears in that accessory drive assembly. One source does appear to indicate that the pulley driving the belt for the alternator turns at 1.9  times the crankshaft speed.

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Re: Cummins M11 Accessory Drive Question

Reply #3 – May 28, 2024, 08:06:45 pm

The AC drive is driven off the camshaft and it would be half crankshaft speed. The alternator
drive I don't know. Do what Chuck suggested.

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