Speedometer needle jumping - help!

[chemeng]

Hi everyone,

Got a '65 fastback I am slowly restoring and have this problem. It usually starts jumping above 30 mph and gets worse as the car goes faster. It also reads about 10 mph faster than it should, found out the rear end has been replaced and has 2.79 gears in it (next year's project is to put in 3.25's and a posi). I traced down the speedo cable and it is secure, but there is a little transmission fluid leaking from it. Is this the cause and should I just replace the cable?

Thanks in advance, Mike

 

[66stangmeister]

i have that same prob on my 66 that i got in december...me and my dad replaced the speedo cable but it's still off once u go over 30 or 35 like u say. I'm starting to thinks its the speedometer gear thats in the transmission....i haven't replaced that so i don't know if thats the problem. but it probablly is

 

[1965-Mustang]

Maybe this might help?

http://www.mustangmonthly.com/techarticles/173_0401_top/index3.html

Article "Instruments Acting Weird"

Mine does this too. Need to fix this weekend maybe.

 

[66stangmeister]

thanks for the link dude.