I have a Derailleur rear shifter that clicks from 1-7 but can be shifted 3 notches past 7, the gears shift incorrectly when I'm on 1 the gears on 2 and when I shift to 3 it goes to 1 then it won't shift to 4,5,6 or 7.
Does anyone know what could be the problem?
several possibilities including:
* shifter broken.
* cable not routed correctly
We need a LOT more information about the shifter, and pictures to offer suggestions. It might be cheapest and easiest to replace the shifter entirely, depending on what you have.
Shimano has made at least four entirely different types of 7 speed shifters for rear derailleurs over the years that I am aware of, and several different models of each type - resulting in a hundred or so possibilities. Until you share with us, exactly what you have, we are not going to offer much more than wild guesses.
The types are: levers, trigger, grip shift, STI - and there may be more. I have never had any of the trigger type, but have had or have examples of the others.
Replace it with a new SRAM MRX (which includes a new cable) and get new housing - and carefully follow the SRAM's instructions, and will work great. This will cost you less than $20- plus a bit of your labor. A bike shop will charge more than that to look at the bike.
Please note microSHIFT is a competitor to Shimano.