Overdrive button blinking "off"

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Oct 30, 2008 | 08:42 PM

Helene

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Overdrive button blinking "off"

Hello all

I have very limited knowledge when it comes to anything mechanical--eh..so I am seeking help. I have a 99 Ford 350 Dually. Just today, going up a hill, the overdrive light started blinking "off" and my speedometer is not working. Everything else was fine. Gauges ok, shifting ok.
Any ideas? Is there a way of testing to get the troubleshooting codes yourself? Any help is appreciated.

Oct 30, 2008 | 10:06 PM

rbaker6336

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From: Blairsville,Ga

Could be VSS or vehicle speed sensor on transmission or on rear axle
mine done that on occaisions and was the one on rear axle
it is located right of center on top of axle tube

Oct 30, 2008 | 10:08 PM

WhëëlMå1

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Joined: Oct 2002

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From: MA

Welcome to FTE. I know places like Autozone should be able to read your codes for free.

Oct 30, 2008 | 10:10 PM

BPofMD

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From: Millersville, MD

I agree with the VSS diagnosis

Oct 30, 2008 | 10:21 PM

Helene

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Blinking overdrive "off"

Thanks all. So, would it be safe to drive it to a shop or is there a chance something will "blow" on the way? I am about 35 miles from town. Does the "overdrive blinking" relate to a lot of codes not even related to the tranny? I sure hope the VSS is whats going on. Thanks much again.

Oct 30, 2008 | 10:38 PM

micchicken

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From: Eliot Me

Mine has done that once pulling a boat out of the water up the ramp while turning in 4wh. I heard a little thud, the od light started blinking. I took it out of 4 wheel and turned the truck off. Started back up and all was good. Is yours still blinking?

Oct 30, 2008 | 11:17 PM

Helene

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I just started the truck up and the light is no longer there. It is too dark out to check the fluid levels etc but I guess the light being out it good. Do the codes/lights just go out like that?

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Oct 31, 2008 | 12:16 PM

Mark Kovalsky

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Joined: Aug 1999

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From: SE Florida

The light will flash whenever the PCM sees something wrong. As long as it sees the error it will continue to flash. If there error is no longer there it will stop flashing. There is a code stored in memory when the light flashes. It will stay in memory for about a month after the last time the light flashed.

Autozone can't read Ford transmission codes, so don't waste your time there. You'll need a good trans shop or a Ford dealer to read the codes.

Most likely you have a failing vehicle speed sensor. It's developing an intermittent open circuit. You can drive it like that with little risk of damaging anything else. The sensor is cheap, usually less than $20, and it only takes one bolt to change it. It might be worth the risk of just installing a new one instead of paying someone at least 1/2 hour labor to read the codes.