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Slow But Clean Differential Fluid Change

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    Slow But Clean Differential Fluid Change

    Ended up changing the diff fluid in my 2000 MGM not too long ago. I had parking brake work done some years ago and was told at the time that the high price was due to the axles having to come out. When going through my car file some time ago, I noticed that the invoice didn't include a charge for new fluid, which seemed peculiar. I'm guessing they knew the method that doesn't require taking the axles out but charged me for the extra work anyway.

    I was going to do just a suck and fill if I could get enough out, but I discovered recently that the axle vent tube had probably never been on my car since I got it around 2008, and I figured it would be a good idea to take the cover off and have a look. I still did the sucking stage anyway since I didn't want to deal with a stinky mess. Here's a photo of the setup I used:

    Click image for larger version

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    Instead of contaminating the container that came with the pump kit, I used juice bottles with a close enough opening. They were very thin-walled, so I couldn't get much suction, but it was fine in the circumstances. My sleep got messed up that week, so I just laid out relaxing and ended up contemplating vacuum science.

    The time required was somewhat comparable to doing a gravity bleed for brakes. It probably took about two hours to reach bottom, but three bonuses were: 1. the old fluid was already in disposable containers, 2. the fluid seemed to have been drawn off the inside of the diff instead of leaving everything coated, and 3. not a single drop of diff fluid came out when I took the cover off. There was a small area below the level of the sealing surface that still had some fluid, and I just used my fingers to squeegee it out. I couldn't actually see the suction hose inside the diff, so I didn't take a pic.

    I didn't want to mess around with RTV (especially after cleaning the old crap off -- good thing I left my fingernails long), so I used a gasket for the cover. For filling it up, I got a 5L jug of fluid and used a condiment bottle that was probably not quite one quart. Once I figured out how to get it in there, it was the perfect size. Curiously, I couldn't feel the level with my finger even after overfilling it. The damn thing dripped for a half hour with no apparent end in site, so I resorted to sucking some out until it was clearly below the hole. I'd guess that people who overfill it think it's low enough when they see that it just drips and then put the plug back in.

    I put a 2ft piece of PVC tube on the axle vent with a hose clamp (after wrapping the first six inches or so of the tube with electrical tape) and then zip tied it to the parking brake cable and stabilizer bar. Not sure yet if that's going to be just temporary.
    Last edited by IPreferDIY; 11-21-2015, 08:37 PM.

    2000 Grand Marquis LS HPP, a hand-me-down in 2008 with 128,000 km; 175,000 km as of July 2014
    mods: air filter box 'tuba', headlight relay harness, J-mod (around 186,350 km), 70mm throttle body, KYB Gas-A-Just shocks, aluminum driveshaft, ARA3 PCM
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