I will update this post as I had a broken sram x4 8 speed shifter for over a year and I decided I would find the problem and fix it. This may be the same issue with similar shimano shifters. My shifter would only shift the 4 highest gears and then would do nothing. I disassembled it and compared piece by piece with a new shifter.

This was the damaged part:

You can see the top of the edge is worn out. As I have left and right shifters, and the insides are simetrical, I just swapped these pieces and voila, both shifters work as new.

I disassembled a few more broken shifters and they all had this problem. As for how to disassemble the shifters, there are some good videos on YouTube that will explain you how to do it.

Hope this will help anyone out there!

I will update this post as I had a broken SRAM x4 8 speed shifter for over a year and I decided I would find the problem and fix it. This may be the same issue with similar Shimano shifters. My shifter would only shift the 4 highest gears and then would do nothing. I disassembled it and compared piece by piece with a new shifter.

This was the damaged part:

You can see the top of the edge is worn out. As I have left and right shifters, and the insides are symmetrical, I just swapped these pieces and voila, both shifters work as new.

I disassembled a few more broken shifters and they all had this problem. As for how to disassemble the shifters, there are some good videos on YouTube that will explain you how to do it.

Hope this will help anyone out there!