Speedometer issues
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Speedometer issues
I have a 1991 F150 with a 4.9 motor, automatic transmission. Had to replace transmission and speedometer has never worked. I'm being told this model is all electronic and does not have a speedometer cable from the cluster to the transmission and I'm being told to replace the cluster panel. Can anyone tell me for sure whether a cable is required from cluster to transmission. I'm getting a lot of different answers, any help would be appreciated. Thanks, Rodger49
i ain't rite
Joined: Mar 2005
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From: Marlboro Mental Hospital.
welcome to FTE.
as
Daniel said, your truck uses a speedometer cable out of the tail shaft of the transmission.
it is possible they put in a 92 and newer trans that does not have the tail shaft speedometer provision.
as
Daniel said, your truck uses a speedometer cable out of the tail shaft of the transmission.
it is possible they put in a 92 and newer trans that does not have the tail shaft speedometer provision.
Posting Guru
Joined: Sep 2008
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On my 92 I have a sensor (VSS) on the top of the rear diff. That feeds not only the PCM but the speedo as well. I wonder if you could check for that and if you don't have it, would that mean you don't have an electronic speedo? Of course, if you did have the sensor that could feed the PCM and not the speedo...just a thought.
Posting Guru
Joined: Sep 2008
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Curious, with a cable driven speedo, how does the PCM know how fast the vehicle is going? Does it get information from the speedo?
i ain't rite
Joined: Mar 2005
Posts: 65,447
Likes: 5,517
From: Marlboro Mental Hospital.
no idea. i only had diesels with manual transmissions, so i did not have to deal with computers.
however ABS equipt trucks had a tone ring in the rear for the ABS. so maybe the computer gets its info from there.
however ABS equipt trucks had a tone ring in the rear for the ABS. so maybe the computer gets its info from there.
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Fleet Owner
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From: Kentucky
On 2wd vehicles it attaches on the transmission tailshaft. (Sorry, no pic)
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Fleet Owner
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From: Kentucky
On 1991 and earlier trucks the PCM gets it's signal from a dedicated VSS sensor inline withe speedometer drive cable assembly.
Fleet Owner
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From: Kentucky
Perhaps I should have been a little more explicit. The VSS signal to the PCM is for controlling an electronic transmission, i.e. E4OD. If you have a mechanical automatic (AOD/C6) or a manual the signal is not required.
Cargo Master
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From: South Central,MO
Does it serve any purpose on my 89?
Fleet Owner
Joined: Oct 2005
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From: Kentucky
The sensor on top of the rear differential is for the RABS system. When Ford started using the electronic speedometer in 1992 they used the RABS sensor for dual purposes. It's original function, rear anti-lock brakes, then used the PSOM to divide down the pulse count for use with the speedometer and PCM.