Jclemons2123

Rear derailleur won't shift at all..

I can pedal and manually move the mech to small or largest cog with no problem..

But without manually moving it, when just shifting gears it won't move..

I see the cable moving when shifting also inching forwards or backwards..

I did however fray the end of the cable really bad, I then cut it off making it shorter ( could that cause it not to shift at all ) ??

The tension barrel at the shifter is missing ( if there was one there to begin with) but there is a tension barrel at derailleur so I don't think that would be a problem either..

Would a bent hanger or derailleur cause it not to shift at all?

Just trying to figure out the problem here to avoid going to shop as I'm on an extreme budget and have $60 to my name.

Derailleur is a Shimano Acerra
3x8 drivetrain

Huge thanks in advance!!

rosefarts

Cable tension moves it up, slack moves it down.

Somehow, you are losing the tension the shifter creates.

Easy
-Loose bolt
-broken cable
- housing slipped off the braze on

Medium
- cable frayed or rusted inside housing
- housing ends are blown out
- snapped deraileur hanger

Hard
- mechanicals inside shifter are stripped


There's lots of other stuff that can cause bad shifts but not too much else that can cause no shifting at all. I

I were to guess, based on extremely low info and no pics, I'd say the housing is slipped through the braze on where you thought a barrel adjuster ought to be.

Jclemons2123

By housing do you mean outer cable? Or referring to only where I thought the tension barrel ought to be? The outer cable or housing is not lining up with the places on the frame as I had cut the cable... Therefore the angle of the cable is a bit different as it's pulled tighter do to cutting it shorter given it had frayed

DOS

Since the cable seems to move when you shift, best guess is you simply don’t have enough tension. Its also possible that you did not have the shifter set in the correct setting when you attached the cable to the derailleur.

Suggest you start over. Disconnect the cable from the derailleur and turn the barrel adjuster back into the derailleur.Check to make sure the housing (outer covering, usually black, that the inner shifter cable runs through) is correctly seated in the shifter and all the cable stops along the frame. Check to make sure derailleur cage is aligned directly under the small cog of the cassette. If it is too far outboard turn the high limit screw in, if too far in, turn it counterclockwise. Reattach cable to the derailleur, pulling it as taught as you can as you tighten the bolt. Check shifting and adjust tension with barrel adjuster as needed to dial in shifting.

rosefarts

I have a little more information now.

You have cable housing, plastic coated and filled with wires. Inside that is the cable. You have to use those terms or people will be confused.

The housing must be butted against hard stops. The frame, shifter, and derailleur are those hard stops. It's usually segments to keep the friction down. If the housing is not firmly into each of those places, the housing itself will move during a shift and never move a derailleur.

From the shifter, make sure the housing is long enough to run to the first stop on the frame and allow for steering. The caps that come with housing will boost longevity from weeks to years. Use them. The housing at the derailleur needs to be long enough that it won't cause kinks or sharp bends. It sounds like you ruined what was on the bike and will need more.

Badly frayed housing is from using side cutters. Do you have a shop that will let you use actual cable cutters?

Set the cable up like the post above me described. It should work.

Only other thing is you must buy shifter housing. Usually called SIS. Has a bunch of straight wires running through it. If it looks like a tightly coiled spring, it's only for the brakes.

Eggman84

Lots of videos on teh Interenet how to change shifter cables. One that I think is fairly good is .

Question, if you manually pull on the cable does the rear derailleur move?

DOS

One other thing, which I alluded to in my earlier post but then left out in the step by step stuff, before attaching cable to the derailleur, make sure you have the shiftier clicked all the way out to its highest gear setting. This will set the cable at its maximum length for attaching to the derailleur with chain on the smallest rear cog.