ST-A410 Shimano Shifter/Brake Combo Repair

(Right hand, rear derailleur) Published in the hope that someone else can use the info I've gained. The drawings are crappy but I think they'll get the point across OK.

Initial Issues

Part came off the Superstrada. When cold, small (shift up) lever moves freely without doing anything.

Replacement part: Allegedly the large (brake) lever didn't return back to neutral very well.

Troubleshooting

There is a little part like this that's supposed to be pushed down by a spring, and engage with another part when the small shift lever is moved. In my assy, the spring (hooks on that notch) was all mangled, providing little to no torsion, and the lube was gummy. Therefore when the lever is pressed it didn't engage and slid right past.

Couldn't get the spring bent back into a usable shape. Couldn't find a good replacement spring online. So I bought a new-used assy on ebay for parts.

Disassembly

To get to the inner assy, see this RJ video. From there, the inner assembly (Part 6AE 9803, "R.H. Release Lever Unit & Small Parts") can be disassembled starting with the castle nut on the outside. I used a dremel with abrasive wheel to cut a little socket into the right shape, but I'm sure there's a tool for it.

Clean and lube

Use degreaser and get all the gunk and old lube out. I soaked all small metal parts in a tray for a while, and used a toothbrush and tweezers to scrape/brush them clean.

For new lubricant, I used a generous helping of Tri-Flow.

Reassembly

Having an assembled one to reference was critical. I felt pretty confident I wouldn't need it when disassembling, but would have been in big trouble without. Even though I wrote down what order parts went off, I didn't record orientation of springs and other pieces. If you do this yourself I recommend filming the disassembly.

Parts List
Order Type Description ID OD h Details
1 Fastener Screw   2.88 8.08 Countersunk
2 Nut Retainer 2.43 6   Square metal
3 Fastener Screw   4.91 15.7 Hex external
4 Spring Torsion spring 8.18 10.63 1.21 2.75 turns 270 deg
5 Spacer Plastic spacer 5.03 7.01 3.04  
6 Spacer Plastic spacer 5.02 7 8.17  
7 Nut Castle Nut 7.24 10.85 4.33  
8 Washer Lock washer 8.33 11.92 0.86 11.92 narrow slice, 14.95 circular part
9 Structure Bent metal end        
10 Spacer Plastic sheet 8.06 32 0.25  
11 Spacer Metal disc 8.06 25.52 0.89  
12 Spring   17 19.11 0.74 2.25 turns
13 Structure Plastic trim        
14 Spacer Step up 8.03 13.85 4.6 Smaller OD 9.99, height 2.48
15 Shift lever   10.03 16.75 2.06 Pin OD 2.99, height 7.21
16 Washer Brass or copper 8 14.04 0.48  
17 Structure Stamped washer-like 8.06   1.03 Smaller ID 3.01
18 Spring Torsion spring 5 7.13 1.01 4.25 turns
19 Structure Stamped washer-like with pin 10.06   2.02 Smaller IDs 3.01
20 Spacer Simple 8.03 10 2.19  
21 Structure Stamped washer-like 8.08 14.55 0.85 Two notches
22 Ring   13.41 15.94 1.48 7/8 turns
23 Spacer Double layer 7.98 11.07 3.33 Smaller OD 10, height 1.75
24 Structure Stamped washer-like 10.03 16.3 1.7 Notches and bend
25 Spacer Tube 3 4.55 5.75  
26 Snap ring Smaller one   4.58 0.46  
27 Structure Stamped washer-like 8.04 14.94 1.28 single wing
28 Mech Hook rachet 3.48   3.46 Smooth curved inside surface, 3.37 smaller thickness
29 Snap ring Larger one   5.51 0.43  
30 Mech Hook rachet 3.5   2.48 2.29 smaller thickness
31 Mech gear 10.88 18.03 2.95 13.11 larger ID. 3.45 ridge thickness
32 Mech gear 10.88 18 2.4 13.11 larger ID
33 Spring Torsion spring 13.56 14.97 0.71 4 turns
34 Structure Cast chunk 9.25 13.05 12.51 Smaller thickness 6.46
35 Structure Stamped washer-like 8.04 17.7 1.36 Post 4.6, 3.48, 2.97 OD
36 Spacer   7.97 10 3.52  

Table generated using table-magic