91-125 Remove/Install Gear For Backrest Adjustment

91-125 Removing And Installing Gear For Backrest Adjustment
















Installation note
The clamping pins in the backrest locks have different lengths and are therefore not interchangeable.

Backrest lock - inside of seat
Clamping pin length 30 mm
Dia. 3 mm

Backrest lock - outside of seat
Clamping pin length 37 mm
Dia. 3 mm

The gear screws (5 and 9) on the left and right gears have different screw head lengths and are therefore not interchangeable.
The screw with the screw head length of 12 mm is for the gear on the inside of the seat.
The screw with the screw head length of 18 mm is for the gear on the outside of the seat.
The threads on the gear screws (5 and 9) are micro-encapsulated and must be replaced after disassembly or coated with screw securing agent.
Tightening torque: 35 Nm.

Removal, installation
Gear on inside of seat







1 Unscrew mount on backrest frame and pull flexible drive shafts on left and right out of gear drive shafts.







2 Unscrew screws and remove toothed belt from motor.
3 Screw motor back onto driver's backrest and tighten hand-tight.
4 Unlock backrest and tilt forward.







5 Knock out clamping pin, diameter 3 mm, while holding with setting iron or hammer (arrow).







6 Unscrew screw on outside (arrow).







7 Unscrew screw on inside (arrow).







8 Screw gear spindle out of backrest lock manually.
9 Remove gear.







10 Check plastic bushings, replace if damaged (arrows).







11 Screw gear spindle into backrest lock so that the clamping pin can still just be knocked in.







12 Screw in inner and outer screws.
Observe installation note.
Tightening torque: 35 Nm.







13 Install clamping pin.
Length of clamping pin: 30 mm.







14 Turn left and right gear spindle all the way up against the stop. To do this stick flexible drive shaft onto gear drive shaft and turn manually.







15 Check backrest lock; both locks should catch simultaneously and completely.







16 The backrest lock adjustment can be corrected by turning the gear drive shaft slightly.







17 In the locked state the control cables for the backrest lock should have play of 0 - 1 mm.







18 Install toothed belt and tension. Adjust toothed belt tension to play of 3 - 7 mm at a manual force of approx. 30 N.







19 Install flexible drive shaft without changing adjustment made previously on gear drive shafts.







20 Lock backrest locks and ensure that they are completely locked by electrically checking the microswitches on the left and right (see Diagnosis Manual, Body, Volume 1, Section 4.1, Model R 129).
21 Continue to reinstall in opposite order.

Gear on outside of seat
22 Remove flexible drive shaft (arrow).







23 Knock out clamping pin, 3 mm diameter, on backrest lock while holding with setting iron or hammer (arrows).







24 Unscrew screw on outside (arrow).







25 Unscrew screw on inside (arrow).







26 Pull stop cable down and out (arrow).
27 To improve access to the gear spindle disconnect pull cable for backrest release on backrest lock.







28 Unscrew gear spindle manually on backrest lock (arrow).
29 Remove gear.







30 Before installing gear check plastic bushings, replace if damaged. Install both bushings with the collar pointing inward.

Plastic bushing on inside







Plastic bushing on outside







31 Insert gear into backrest strut and turn gear spindle into backrest lock until the clamping pin can still just be knocked in (arrow).
32 Hook in and clip on control cable for backrest release.







33 Screw in screws on outside and inside while inserting stop cable; do not pinch cable eye.
Observe installation note.
Tightening torque: 35 Nm.







34 Install clamping pin.
Length of clamping pin: 37 mm.







35 Turn left and right gear spindle all the way up against the stop. For this purpose stick flexible drive shaft onto gear drive shaft and turn manually.







36 Check backrest lock; both locks should catch simultaneously and completely.







37 The backrest lock adjustment can be corrected by turning the gear drive shaft slightly.







38 The pull cables for releasing the backrest must be adjusted to a play of 0 - 1 mm in the locked state.







39 Install flexible drive shaft and screw onto backrest frame with mount without turning the previously adjusted gear shafts.







40 Lock backrest lock and ensure that they are completely locked by electrically checking the microswitches on the left and right (see Diagnosis Manual, Body, Volume 1, Section 4.1, Model R 129).

NOTE: When the front seat backrest is completely locked a play of 15 - 20 mm is permissible at the top of the backrest.

41 Continue to reinstall in opposite order.