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I have a 1949 F68 (F2) that I am having speedo issues. I have a 8 cylinder flathead engine and I put a heavy duty three speed tranny from a 1952 truck. The rear end is out of a 72 F250 with 3.54 gearing. The problem is the speedo cable whines and the needle jumps all over the place. The original tranny was a 4 speed crash box. What would be causing this? Is the gear in the tranny that runs the speedo cable different between the two transmissions? I assumed the gear in the transmission would be matched to the transmission and should not affect the speedo cable or gauge. Any help would be appreciated. I know everyone likes pictures ,so here you go. , Doug.
Doug, sounds like the inner cable is in need of some lube and is getting caught up on the casing. Either graphite or they make a light oil for just this thing.
If you disconnect the housing at the transmission you should be able to pul the inner out and see what shape it's in and of there is anything it's snagging on.
check the cable where it attaches to the speedometer for wear and that it's in deep enough, also you might want to lube the cable assembly. Not sure about the trans gear but check that for wear too.
Good luck Doug........ nice project ya got going.
, Doug. 
