Instructions for thumb installation _with quick change_ by fdh56iuoui



            CAT pin grabber quick change modifications.
Remove bucket from quick-change coupler
Remove quick-change coupler and grind area shown here.
Use gray plastic gage furnished with QC thumbs to determine how much to

                                        Use heavy grinder to remove material
                                        from this area.

Gage should set flat on inside of QC when finished. After grinding this area,
use a disc sander and/or a die grinder to radius and blend corners.

Leave no sharp edges that may give cracks a place to start.

Before installing bucket, slowly cycle bucket cylinder all the way out.
The cylinder travel should be stopped when the bucket toggle link hits the top of the
quick attach casting.
If the quick attach starts to bind up against the South Fork cylinder brackets before
the bucket cylinder reaches its’ limit, the quick change bracket will require more
grinding in this area.

                                             Alternate method to
                                             limit bucket cylinder
                                             3/8 x ¾ flat bar
                                              2 ½” long
                                             welded to toggle link.
Thumb installation
Non quick change type shown.

                                   Extend E-stick about 2 ft.
                        Bring stick into a vertical position as shown.
                        Place cylinder and brackets behind boom.
                        Loosen the (4) ½” bolts so there are only a
                        few threads left holding.

                       Place arms over pin boss and snug bolts.
Note: half round cutouts face cab.

                  Swing arms and cylinder up and
                   secure with 5/8” bolts and top
                  clamp as shown.
                  Use a 1 ¾” wrench to turn lower
                  clamp if necessary.
                  Tighten the (2) 5/8” bolts evenly to
                  keep the cylinder arms an equal
                  distance from the bottom of E-stick.

                  Note position of bucket cylinder.
                  This will give room for an impact
                  wrench when installing top clamp.
Install bucket (or coupler) using
 dummy pin.
Position bucket just off the floor
so there is no weight on pin.
(leave bucket off for now if you
have a quick coupler)
Get thumb into position and drive dummy
pin thru using alignment stub to protect
threads on pin.
Use the washers that came with
bucket to shim thumb if necessary.
Remove alignment stub and install
washer and self -locking nut.

             Use factory washers on non QC
             On Quick change installations,
                use the 5/16 tabbed spacers      Alignment stub
                       furnished with thumb.

                          Grease zerk
                          faces away
Extend cylinder rod.      from cab.

Swing rod end into
thumb and install
cylinder pin.

Do not use spacers on
either side of the
cylinder rod.
 It must be allowed to
float as the arms flex.


            Parts Needed: (1) CAT #1770856 Tubeline (420D) #1772041(430D)
                          (1) CAT #1772171 Tubeline (420D) #1775156(430D)
                          (2) CAT #9R1004 Clips
                          (2) CAT #9R1005 Clips
              Also Needed: 5/8” Hole saw and small right angle drill.

                 Move existing tubelines in as shown below.

                                                             Original tube

                                                              Added tube

                                                          VERY IMPORTANT RH factory hose must be
loosened and rotated out as shown or it will hit fitting boss on main cyl when cyl is fully extended.

Use a 5/8 hole saw and a small right angle drill to make new holes thru rubber clamp blocks on main boom.
By chucking pilot drill and using it to drive hole saw, it is easier to clear the rubber slugs by loosening
setscrew and pulling the saw off the pilot drill. This also allows use of a smaller right angle drill or die

After installing new tubelines, they may have to be “tweaked” to keep them from rubbing against the original

                 Alternate tube mounting with hammer circuit return hose

When the tractor is equipped with factory hammer circuit tank return, it is not possible to run the tube
lines thru the clamps. They must be routed as shown here.
Drill and tap the plate on the clamp closest to hinge point and bring the tubes to the center as shown.
(It may be possible to use existing bolts and leave the tubes spread out at the bottom clamp on a 430D, but
on a 420D the hoses will strike the swing frame when the main boom is fully retracted.)

Remove bar and
shorten this end ¼”.

                                       Force this line down and
                                       clamp as shown.
                                       Run new tubeline as

                                               Hose Routing

Connect the 45° ends on the shorter of the two long hoses to the new tubeline on the LH side. Follow existing
hoses to bring this hose down the LH side of the bucket cyl. Use light zip-ties to temporarily secure hose.

                                                               45° hose end
                                                              LH hose should go to
                                                              lower bulkhead fitting

 Connect the 45° ends on the longer hose to new tubeline on RH side. Route new hose as shown.

                                                             New Hose

                                                             Place washer under clamp
                                                             so new hose will not be

Follow existing hose and route over the top of the bucket cyl to run parallel with the new LH hose. Do not
permanently secure these hoses until the end of installation. While the E-Stick is cycled in-and-out and the
stick boom is cycled thru its full range of rotation, check for any hose binding or pinching.

---Optional--- After hoses are routed to your satisfaction, they can be secured using CAT clamps
part # s 5P7462 clips, 5P7463 clips, 6V-0683 grommets.

Install bulkhead fitting clamp on bucket cyl. (17” from front of cylinder)

                                                       Move this grommet
                                                       back and down.

                                                       Bulkhead fitting clamp

twist in hose as the fitting is tightened at the bulkhead clamp.

                                                                             Pinch point

                                                                   20” python strap

                              Add hose wrap.

                                Make sure RH hose doesn’t hang up on this
                                bracket as E-stick is cycled in & out.

  Before installing anti-cavitation port reliefs in control valve or connecting hoses to valve, check main
  relief pressure by operating pedal with ports plugged. Note this pressure. When adjusting thumb
  pressures later, the clamp pressure should be set at least 100 psi lower than the main relief. This assures
  the port relief is unloading and protecting the thumb and its components.

         1 1/16

17mm                                                       Lower hose to
                                                           LH tubeline.

                                                         Add port relief
  9/16                                                   cartridges

  Remove blank plugs from control valve and replace with the port relief valves. (supplied with thumb) Before
  installing cartridges, back adjustments out until you feel the spring “let go”. Then turn in ½ turn. This will get
  you close. Set port pressures before removing the #12 plugs and running the 58” hoses. It is a little easier to set
  the top port relief without the hoses in the way.

  Set pressures
  Clamp pressure (bottom relief) to be set 2950 – 3000 psi but at least 100 psi below main relief setting. This will
  result in a condition where the bucket will over-ride the thumb until the thumb is 90° to the stick. The thumb has
  its best leverage at this point, and the bucket and thumb will be stalled. One cannot over-ride the other.
  Retract pressure to be 1800 – 2000 psi. (top port relief)

                      Drill hole opposite this
                      hose & move this hose
                      over to new hole.
                                                                          8” python strap

Use 58” hoses to connect control valve with new tube lines.

After plumbing is complete, fully retract E-Stick and cycle thumb to a position 90° to stick boom. Check
clearance between bottom of stick boom and back of cylinder. Keep in mind that this clearance will change as
wear strips in boom wear. If clearance is less than ¾”, move cyl
down by placing flat bar between stick boom and lower clamp block.



NOTE: Tooth adaptors are shipped loose. When using more than one bucket, it may be necessary to move thumb
teeth around to get a good nest with all buckets.
It is not uncommon to have to gouge teeth off some buckets and re-arrange them to make them nest well with the
Teeth must not hit tip-to-tip but should interlace.

When satisfied everything will work O.K., remove the (5) ½” bolts and loctite them. Lube all 5 zerks. Fill
hydraulic tank to proper level.

If you have any questions or problems,
please call Russ Salvage at South Fork Industrial, Inc. (541) 258-7696.

To top