02-Z66,,,
I in no way neglect embracing preventative maintenance... To each their own... Personally, I will be chenging my rear diff lube at 50,000 miles when the transfer case is due... I was just letting you guys know the manufacturers recommendation... Take it with a grain of salt; that's fine... But when I see folks changing fluid at 10,000 or less, it's, I believe useless... I am not saying folks performing their own maintenance don't perform it properly, but I will say that pulling the cover, and cleaning the mating surfaces of the gasket can be an involved task... You risk getting contaminants into the housing, and also risk a leak if the gasket does not seal... The gaskets rely on themselves to be dry, and once they exhibit a leak, they are junk, and need to be replaced with a new one...
So in short, draining expensive fluid, pulling the cover, cleaning surfaces, re-applying diff cover, and filling to proper level is not difficult, but it opens the door to possible issues if not done perfectly...
The diffs we have are considered light duty in comparison to all consumer and commercial trucks... The fluids I list above, are used in some of the largest diffs available under much greater loads than our AV's can produce... These commercial, high load conditions in those types of vehicles are exponentially beyond what we will ever put the fluid through in the diffs of our trucks... But, again, the lubes in the commercial conditions are rated at the 500,000 factory fill spec...
I don't fault anyone for dumping their diffs, and doing frequent maintenance. but let's be honest, 10,000 to 15,000 miles is too early, and a waste of money... Not to mention opening a perfectly sealed differential, and possibly allowing foreign material into the housing while cleaning your mating surface... why? why?
Believe me, if Eaton is gonna stamp a 500,000 mile factory fill, and a 750,000 mile extended warranty seal of approval on a lube, then I'm sure our little AV diffs can tolerate 50,000 or better...
If you must change the fluid often, just drain it through the plug, and keep the cover intact ... Cleaning the magnet is an over rated objective... Gear sets wear, and spawl throughout their life, and the magnet safely contains the larger more damaging particles... If you pulled the cover every 20,000 you will see a normal build-up of fine wear metals that is normal... Even if you pull heavy loads regularly, the lubes have the EP additives to live a long service life... The days of cruddy mineral gear lube that needs frequent changing are over... And by the way, don't knock the oil life monitor... I have seen many oil sample wear metal tests ?that prove oil can last well beyond 3,000 miles... Oil analysis is a direct reflection of projected oil life... The truth is, GM sets limits on certain things, and incorporates the wear metal limits among others... The 10,000 mile interval is BEST CASE and I have never seen or heard of a light going that long... But, running a good GF-3 oil for 5,000 to 6,000 miles under normal service is fine... The LM7 is an extremely clean burning motor, and oils now are superb... Raw fuel, oxidation, and moisture is what kills an oil... The motors we have are so effecient, that the oils don't have to absorb what oils in 1980 were required to... In comparison, the rear diff lube has only 2 avenues of contamination... Moisture, and wear metals... That's it... No fuel, combustion contaminants, acids, yada, yada ... Diffs lubes don't get stressed like motor oil does...
If you want to be concerned about a lube change frequency component, be concerned about our AutoTrac transfer cases... They will be the first to fail as a result of contaminated fluid... The viscous clutch drops material continuously... I haven't heard anyone mention they changed their TC fluid as often as the rear diff for sure!
Here is a couple links to explain what these new lubes we use are, and what they accomplish:
http://www.pzlqs.com/Tech/Pdsheet/D...sion/Pdf/LongLifeExtendedWarrantyGearOils.pdf
http://library.cbest.chevron.com/lu...5f870014c4ab?OpenDocument&Highlight=0,75W-90*
I'm not trying to pick a fight here, but I just feel some of us have some pretty strong opinions about preventative maintenance, and cherish our investment... All I'm trying to poin out, is that 20 year old or even 10 year old wisdom is not always accurate, especially in this case... The fact that someone will pull a cover, and risk contamination at a mileage so low is beyond me... All it takes is a single 1/8" piece of gasket or rag to render the G80's locking function inoperable...
But, if you can be meticulate about your procedure, and want to pay $90 for lube, and go through the effort to do it right, by all means, have at it!
It's your $$$, and I can't tell you how to spend it...
11H