Volvo Penta AQUAMATIC 280 Workshop Manual page 60

20. Remove the double bearing box when the correct
backlash has been obtained.
To gain a clearer picture of the contact pattern, coat
the gear teeth with a thin coating of marking dye.
Then install the double bearing box again.
NOTE! The cover is still installed with an excessive
number of shims!
21. Rotate the gears in the normal direction of rotation
(clockwise) while at the same time braking the gear
forcefully by wedging a wooden brace against the
gear cups. The marking dye will be pressed away
from the point of contact on the gear tooth face,
which will show a picture of the contact pattern.
22. Dismantle the gear set and compare the contact
pattern to that of the picture "A". This picture shows
the desired pattern for the drive side of the forward
and reverse gear. The drive side is the convex side of
the gear. The dye pattern should be nearly oval in
form and be positioned half way up on the gear tooth.
It should be displaced towards the small end of the
tooth (towards the gear cup) but not running off the
end of the tooth.
23. If the dye pattern reflects a contact pattern as
shown in picture "B" the shim thickness underneath
the drive gear (double bearing box) must be reduced.
The drive gear then moves towards the driven gears.
The driven gears must then be shimmed out the
same amount to maintain the correct backlash.
Repair instructions
57