fishboat

I recently had a bike shipped to me that has a set of Shimano M739 (3x8) shifters on it. Prior to shipping the right, 8-speed, shifter worked fine. When I received the bike the right shifter is stuck in one position. I don't want to force it, but I've tried a number of times and the shifter just won't budge more than a tiny amount. I pulled off the cover to change the cable and it looks like cable-head is in the right position(I thought with the handlebars removed for shipping and a loose cable, the head of the cable might have gotten out of place and jammed..it doesn't look that way). There is a metal piece that seems to be rotated into the shifter a bit, that rotates behind the cable head, that prevents me from pulling the cable out. That piece won't move and I suspect has something to do with the shifter being jammed. It doesn't appear the shifter itself suffered any damage in transit, but it must have gotten hit..or something..during shipping. The bike was packed reasonably well, bars/stem were out of the headtube, wrapped and taped tot he seat tube. The shipping box appeared undamaged in that area.

I've taken mtb shifters apart with mixed results in the past. One cleaned up and reassemble intact easily while another was one of those.."I really wish I hadn't taken this apart" as it took a long while to get it back together and working well. Neither were an M739 XT, so no idea what to expect.

Note: This isn't a "dirty-stiff shifter that can be loosened up with WD40" issue. The shifter movement is jammed.

Any ideas?


Top of shifter

Under side of shifter, taking cable cover off

Cable cover removed


Current, full range of motion.

70sSanO

My guess is that the shifter was not in the "1” shift position and the cable head worked its way inside the mechanism and is wedged in there.

Here is an exploded view...
https://si.shimano.com/en/pdfs/ev/SL...-M739-1638.pdf

These videos show how to disassemble, but if you can get to the cable head, and dislodge it, that might solve it.



John

Edit: Changed shifter position reference for correct top normal RD.

Crankycrank

Try firmly pulling on the cable while trying to shift in either direction and you are right not to force anything but give the cable pull a try.

fishboat

Combine both of your responses and I think you (you's?) have it. It took a fair bit of pulling on the cable while futzing with the shifter up/down, but the assembly holding the cable head finally lowered into the 1 position. I then tensioned the cable properly in the rear derailleur (the bike shop that packed it loosened the pinch bolt on the rear derailleur to get slack to remove the stem/bars) and I think it's working. I'm booked this eve so I can't finish the shifter/rear derailleur setup, but I think...hope..it's working again. I'll know in the morning.

THANK YOU!

It's such a nice shifter..I'd be bummed if it wasn't working. Other than this issue, the bike seems to have come through the shipping process unscathed (whew).

Crankycrank

I'll add that anytime you are shifting an indexed shifter around, road or MTB, keep tension on the cable if it's loose or detached from the derailleur so it doesn't jam things up.

dedhed

You're a Sconnie, so you know "Youse guys" is the proper response

fishboat

You betcha! Ya..that's it. I knew there was a 'proper' way to spell it, but I was having a brain-fade moment. I haven't spent enough time in Cudahy-down-by-the-sea lately.

fishboat

Yep..good advice. This was partly the bike shop packer's fault(not shifting it down before breaking things loose) and partly mine. Anytime I remove/install shifters I always make sure to shift them all the way down. After dealing with this issue I can see a shifter with a cable installed really needs a fair amount tension on the cable to work properly. Lesson learned..thx..

fishboat

Update:

I setup the shifters/derailleurs as they should be and both shifters are working perfectly. Just a light touch-click in either direction and the chain drops/steps up into the next gear. No muss, no fuss. Sigh.

Thanks folks!

KCT1986

I run those shifters on 2 bikes. The cable tension setup is the same as normal shifters, no additional tension needed.

The only difference is when the cable is totally de-tensioned, like unhooking the derailleur. If not in the small cog/chainring position, the cable hook can swing outwards and jam against the outer body.

Shifting to the neutral position before doing any work will prevent any issues. If it does get jammed so bad that jiggling doesn't work, it's easy to remove the shifter unit from the bracket.