Subject: Rear drive pressure
Author: Greg Bender
Date: Apr 20, 2005, 8:45 AM
Post ID: 1718733320
Okay, I'm going to weigh in on this one...although I'm no expert. So,
feel free to banter my opinions around and dismiss them as mere
gibberish if you don't agree.
It is my understanding that pressure builds up inside the rear drive
(due to heat expansion, etc) and that a certain amount pressure is
desireable.
Too much pressure will push too much of the gear oil up the pinion
carrier and into the swing-arm. Yes, it could migrate to the
transmission, but I don't see that as the major concern. I think the
main problem is that the rear drive will be starved of gear oil and
lubricating and cooling qualities it needs. (My understanding is that
the cooling properties are much more valuable than the lubricating
properties).
Too little pressure and not enough gear oil will get pushed up the
pinion carrier to lube and cool the pinion bearings, especially the
fore-most bearing. The result will be that the pinion bearings will
become starved of oil...as they will rely solely on splash lubrication.
Guzzi has not vented most rear drives (with few exception) to this day.
Also, Guzzi provides no means to prevent gear oil from going into the
swingarm. By design, it's free to go there. Therefore, I see no good
reason to vent *most* Guzzi rear drives, and the loops are in that
category. The swing-arm itself provides an expansion chamber for the
rear drive oil.
I do know people who - as a matter of routine - vent all of their rear
drives. These people also don't report any problems (at least to me,
anyway). So, it is perfectly possible to vent the rear drive and have
the pinion bearing sufficiently lubed and cooled to last a really long
time. Nevertheless, I won't be venting my rear drive (unless I can be
convinced otherwise :>).
All this being said, I do think it is important to 'burp' the rear drive
after the gear oil is changed. Take it out for a ride long enough to
heat up the gear oil (just feel the case to see if it is warm) and then
remove and replace the filler plug. You'll probably hear the hissing
sound and you may need to do it once or twice. My reason for
recommending 'burping' is because I think it cuts down on excess
pressure.
As for the large magnetic plugs, I use them on the engine drain,
transmission fill, and rear drive fill plugs. All three of them collect
some particles - which I remove when I change oil.
Regards,
Greg Bender
1971 Ambassador
2000 Quota
http://www.thisoldtractor.com/gtbender
Florida MGNOC website
http://www.thisoldtractor.com/fl_mgnoc
Minnesota MGNOC website
http://www.thisoldtractor.com/mn_mgnoc