Details(or some of them)
I have had rear end problems - it was replaced once and a new ring, pinion and pinion bearing the second time. The failures both began with factory fluid, but the first problem, where they had to replace everything, had Amsoil in it when I took it in and it was produce lots of metal flakes. After that it had factory fluid for the next 10K and then they had to replace the ring and pinion. They took extra care to set slack in the gears that time and took the blame for the second problem.
I ran that factory fluid for many miles without a problem. (I could tell you how many but it would take more time). Then I installed a Mag-hytec cover and put Amsoil in - within the week I started feeling the grinding on corners that I had felt before the failures. I made 3 of 5 identical loads with that fluid that week. Changed the fluid to an off-the shelf 75-90 and the grinding almost completely dissappeared on the last 2 loads and since then. Also, there were long metal "flakes" the magnets when I changed the fluid. Since then I have notices that the metal produce by the rear end in more of a sludge without Amsoil, but flakes with sludge with the Amsoil. I also notice that Amsoil now has a "Severe Gear" fluid - ummm, I thought their fluid I was running was made for severe use - IMO - that shows that something in the normal 75-90 was not good enough!
Also, I was running extended oil change intervals and having my oil analyzed, based on others' experince with Amsoil engine oil a bypass filters. During that time I installed an Amsoil air filter, the next oil analysis came back with dirt ingestion and high wear metals. I immediately put the factory type paper filter back in and have not had a significant increase in dirt in my oil since. To recap about the air filter - paper filter for three samples - minimal increases in silicon and wear metals - Amsoil air filter high levels of silicons and wears metals - back to paper, back to normal. There are studies cited on some threads here on TDR that show some air filter test results. I would recommend to anyone "playing" with the air filters on these trucks to have your oil analyzed - and establish a base line. I am sure these engines can go a long time with some fine dirt, but I need my truck to last about 400k and I don't think it would if I left that Amsoil filter on.
I now use a company called Lubrication Engineers in Fort Worth. The salesmans name is Dick Darmon 800-537-7683. I agree with them - just because it is sythetic does not mean it is best for the application - they make both syn and non syn. After I saw their logo, I realized I had used their products before in an industrial application. The place that I was working for at that time said it was the best gear oil they had seen.
I have since replaced all fluids in my truck, except for the front end, to get rid of the Amsoil.
Lots of money down the drain!!!!!
I can provide more exact mileages and dates on changes etc. if anyone need them.
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