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08-07-2012, 06:00 PM #1
Gear head said not to use synthetic in diffs and this is why!!
I was talking to a guy that rebuilds front and rear differentials for the past 30 years and he told me that synthetic oils are great. But not for the differentials. He said the reason why you shouldnt use it is because conventional gear oils push the contaminates to the side walls of the diff cases and it sticks there not allowing it to be continually ran through the gears and bearings. He said that he has seen bearings shot after about 50-60k miles because of this. He said that synthetic oils are the best for any system that is filtered but diffs are not. And the properties of the synthetic blends do not allow any wear contaminates to stick to the sides like the conventional oils. I guess if you continually change the oils maybe this statement may not apply. But then at what interval would be acceptable to not allow any of the contaminates to wear on the bearings ect. Just thought I would share an opinion.
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08-07-2012, 07:43 PM #2
Maybe, I'm not buying into it though, synthetics are so much better than conventional grease, there is just no comparison.
Some reading: http://www.sinwal.com/data/The%20Stu...ar%20Lubes.pdf
The Amsoil Severe Service lub toped the tests, followed closely by GM's brand.
'09 Avalanche LTZ - Black
'05 Envoy XL (sold)
08-07-2012, 08:51 PM #3
That is a lot of testing that is for sure. I guess my only thought on the tests are that it really doesnt put any of the oils through its real life scenario such as the time factor involved. If these tests could be conducted over a period of 4 and 5 years including the temperature changes in that amount of time I may lean more to agreeing that the synthetics do what they say. I think I would lean more to using synthetics in my diffs when I change my gears soon and just change the oil out often. Afterall I did buy a rear diff cover that has a drain plug in it.
08-08-2012, 11:48 AM #4
GM diffs (especially the front one), have a habit of picking up water, changing the fluid more often than the recommended interval is not a bad idea (unless you get it done at a GM shop).
08-08-2012, 07:55 PM #5
They push contaminates to the side walls of the diff case!!?? WTF and OMG. You know my dad had a car that only took a key to run. I know this for a FACT because I never saw him change oil or put gas in it so it had to be the key. I wonder what ever happened to that car. I think I was about four or five when it went away and then he got this truck that he was always putting gas in. How is it that old saying goes--- Believe half of what you see and none of what you hear.2000 GMC YUKON SLT, 5.3L tow pkg, G80 rear/w 3.73 gear
08-08-2012, 07:58 PM #6
Last edited by Pikey; 11-30-2012 at 07:10 PM.
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08-08-2012, 08:02 PM #7
08-08-2012, 08:15 PM #8
So if you drain the oil out, then pull the diff cover, obviously all of the contaminates will not be suspended in air. So how do you find out how true this is. Remove the entire rearend out of the vehicle, put it on a bench and pull the cover off facing up and look inside with the oil still in it??? suck the oil out and see if the contaminates are against the walls of the housing? what prevents the contaminates from sticking to any of the other parts inside that dont move. I dont know. It sounds like a possibility that it may be true. But we could also argue that synthetics are so good that there are no wear contaminates to worry about.
08-08-2012, 08:34 PM #9
"But we could also argue that synthetics are so good that there are no wear contaminates to worry about."
I'm going with this one
08-08-2012, 11:50 PM #10
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If this mechanics theory were true you wouldnt need a filter on your engine, all the contaminants would be stuck to the sides of the oil galleries, I've broken open quite a few engines, gear box's, and axles running Synthetics and none of them had anymore contaminants sticking to the sides than there was on parts using conventional dino oil.
When I used to work on Jets we had huge oil pots for the main induction gearbox's that unbolted from the bottom of the gearbox that you dropped straight down then tilted to drain the oil into a bowser, we used synthetic oil for all the engine lube and after dropping over at least a 100 oil pots in a 20 year career I've never seen what that mechanic describes happen, the contaminants were always mixed in the lube.
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