Speedo question
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Joined: May 2002
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From: Richardson
Speedo question
[updated:LAST EDITED ON 27-Jun-02 AT 03:10 PM (EST)]1989 F-150 4x4 351w c6
My speedo reads way faster than I'm going at highway speeds and slower at low speeds. I have oversized 33" tires. Left side has been wrecked so I don't know the axle code or transmission code. I do know that the shift indicator has a "D" inside a circle for the drive position which smells like an overdrive transmission but I know it has a c6 in it cause i just had it rebuilt.
If the truck originaly came with an e4od and it has been switched out to the c6, could it cause these symptoms? The speedo starts out slow then really accelerates fast from about 45 to 75 mph when i am actually accelerating from about 50 to 60. The speedo cable comes out of the transfer case, so i wouldn't think it would care about the final drive ratio of the tranny.
What if the rear end has been switched out to something lower? With 4x4 wouldn't that be a problem if the front doesn't match?
My speedo reads way faster than I'm going at highway speeds and slower at low speeds. I have oversized 33" tires. Left side has been wrecked so I don't know the axle code or transmission code. I do know that the shift indicator has a "D" inside a circle for the drive position which smells like an overdrive transmission but I know it has a c6 in it cause i just had it rebuilt.
If the truck originaly came with an e4od and it has been switched out to the c6, could it cause these symptoms? The speedo starts out slow then really accelerates fast from about 45 to 75 mph when i am actually accelerating from about 50 to 60. The speedo cable comes out of the transfer case, so i wouldn't think it would care about the final drive ratio of the tranny.
What if the rear end has been switched out to something lower? With 4x4 wouldn't that be a problem if the front doesn't match?
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Joined: Jan 2001
Posts: 1,124
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From: Rural Florida Panhandle
Speedo question
All the ratio changes can affect your speedometer, but they would all be in the same direction. That is, if changing a gear makes it read faster at 40, then it would also read faster at 60. If the speedometer is inconsistent in it's inaccuracy, it is defective.
I have one on my 91 Explorer which is inaccurate in the opposite direction from yours. It is a salvage-yard replacement for the original which had the same symptom. Mine is only accurate at 70. Below 70 it reads fast, and above 70 it reads slow. That means the spring is not calibrated properly, and is not repairable. I just live with it.
However, if yours is erratic, then you may have a dust problem or the movement may be bent so that it gets friction connectivity as well as magnetic connectivity between the needle mechanism and the rotating drum.
Winford
I have one on my 91 Explorer which is inaccurate in the opposite direction from yours. It is a salvage-yard replacement for the original which had the same symptom. Mine is only accurate at 70. Below 70 it reads fast, and above 70 it reads slow. That means the spring is not calibrated properly, and is not repairable. I just live with it.
However, if yours is erratic, then you may have a dust problem or the movement may be bent so that it gets friction connectivity as well as magnetic connectivity between the needle mechanism and the rotating drum.
Winford
