1955 Super: Redline speedo only working in reverse gear!

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Posted (edited)

Hi guys,

I'm currently in progress of restoring a 1955 Super. During the winter months the engine and transmission were completely rebuilt.


One of the things I hoped to fix was the speedometer: the speedo never worked before because one of the previous owners (for some reason unknown) removed all of the teeth from the driven gear! So after the transmission was rebuilt a replacement driven gear was inserted and I expected everything just to work fine...


BUT: The speedometer now only works in reverse gear! Everyone keeps telling me that this is just impossible...


To double check I used another redline speedo AND another speedo cable (just in case the other one was twisted inside) - but the effect remains the same: the redline only shows in reverse gear...


I am quite sure that neither the transmission nor the speedometer were ever modified or "enhanced" by some third party parts. When the engine was opened it turned out that it was never ever serviced before...


Anyone experienced something like this before?


Kind regards





Edited by Ralph55
forgot some background info (see edit history)

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Posted (edited)

It isn't impossible, but probably BOTH gears, the one on the cable end and the on the transmission shaft are wrong.


On some cars this is possible, and I suspect it happened with yours. Lets say, for the sake of argument, that the speedometer exits on the driver's side (left, USA) of the car. If the gear engages below the centerline of the output shaft, the teeth have to lean one way, and if it engages above the shaft, the teeth have to lean the other way.


If the speedometer exits the transmission on the passenger side, then the gears for below the shaft become the ones for above the shaft, and vice versa.


Get this backwards, and the speedometer goes backwards. Try to mix half and half, and it just shears all the teeth off.


On a normal speedometer with a needle, and zero at the left, and a hundred and something at the right, the needle goes clockwise. The cable has to turn the same direction as the needle will. It is the only way a speedometer works. Viewed from the back of the speedometer, you have to turn the speedometer shaft counterclockwise. Viewing the cable from the speedometer end, thats clockwise. Viewing the cable at the opposite end, the end that hooks to the transmission, thats counterclockwise. Turning around and looking at the speedometer output on the transmission, thats clockwise.


Try spinning your redline speedometer from the back. If counterclockwise from the back makes it rise, It is like a speedometer with a needle. If it is opposite, just reverse everything in the paragraph above.


Look at the cable with it disconnected at the speedometer end. I'll bet it is going the wrong way.


I think it is time for some part number research and a couple of new gears.



Edited by Bloo (see edit history)

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Be sure they didn't install the tailshaft extension upside down if it has a symmetrical bolt pattern. Does the cable loop over and attach to the passenger side?


Stranger things have happened.



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After some research they discovered that there are indeed ball joints with integrated worm gear which have the teeth in reverse direction (available with a matching driven gear). What happened was that such a set of driven gear and worm gear was ordered during the makeover of the transmission.


The solution was to order a new set with the worm gear pointing in the other direction - which will reverse the driven gears turn direction which then will make the speedometer operate when driving forward.


Strange things happen for sure - but why always with my cars... 😉

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