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Allison mystery hole

July 14, 2011, 03:18:23 am

I was gazing down upon my Cummins M11 and Allison trans from the open bed area when I spotted a hole on top of the Allison.

It is a couple inches back from the engine and is centered on the bell housing, the torque converter (I would guess) is just below the hole.

The hole is about 1/2" and is threaded.

What is this hole for and more importantly what screws in to it?

Thanks, Lon

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Re: Allison mystery hole

Reply #1 – July 14, 2011, 05:25:32 am

I don't know for sure, but I would imagine it is for another place for a speed sensor and is not used in your application. Just my guess though.

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Re: Allison mystery hole

Reply #2 – July 14, 2011, 10:22:57 am

I don't know for sure, but it could be one of the spots where they screw a eye bolt in to lift the tranny out when separated from the engine.

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Re: Allison mystery hole

Reply #3 – July 14, 2011, 12:02:59 pm

If you look at the bottom of the transmission you will find a threaded hole there too.  The one on the bottom is an inspection hole, not sure what the one on top is for.  If oil  leaks from the engine drive shaft seal it would drip out that hole.  It could be plugged or open. There is a vent on top of the transmission and one should be careful not to spray water from a hose at it.  From memory, I believe it is located on the flat part of the case.  Maybe you are just missing a plug.  Check with Allison.

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Re: Allison mystery hole

Reply #4 – July 14, 2011, 03:04:39 pm

Like the others, it is unknown by most as there are many many otions available. If it is not leaking oil, forget it and worry about something else.
Remember the old saying  "If it aint broke, dont fix it"

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Re: Allison mystery hole

Reply #5 – July 14, 2011, 08:59:23 pm

Here Here Dave M, I agree if it aint broke try to resist messing with it until it is.

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