I have a 34L that I picked up as a restorer that was very well used with 75k km. Pulled engine apart and 5th gear was badly pitted. No oil pump damage at all. Put in a new 3AJ pump regardless for good measure. I have 2 x 3TB's that had pitted 5th gears both after about 65k kms after very hard lives also . I rebuilt those engines to replace 5th gears and found no oil pump damage. I now run magnetic sump plugs now and they usually have a film of very fine metallic grey paste as expected on oil changes so they seem to do the job.
Gear pitting on big singles that do big kms is not just an XT600 issue. The same issue applies to DR650's and others. Because they have such low RPM torque it is very easy to ride them at low RPM which pounds the gears. I was guilty of this! After the rebuilds I changed riding style & change down a gear when required rather than chugging along in a high gear as I used to do. Replacing the cush drive rubbers I also consider important to replace regularly as these really take the edge of the shock loading into the transmission. I always notice how much smoother it feels after replacing old rubbers with new. They generally only last 10-15k kms before they are compressed and hard I find. Finally I now tend to run oil on the heavier end of the scale to theoretically give more protection to the transmission. Winter here in oz I run 20w50 and summer 10w60 ful syn. All good so far, have done 20k kms on one of the 3tb's. I will report back here in a few years to let you know how far they go before the next rebuild!!!
Last edited by dzl; 7 May 2019 at 14:32.
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