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Changing The Rear Differential Fluid


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#1 Dylan

Dylan

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Posted 12 November 2008 - 02:36 PM

Thanks to kastle for posting this up at Scoobymods.

Just a quick page detailing how to change out the gear oil in your rear differential. You are best off replacing the oil with something like Redline 75w90 gear oil, as it is full synthetic and resists the high temperatures that can build in the differential better than an organic lubricant can. It also has friction modifiers which rear Limited-Slip Differential's appreciate.



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There is the object of our search, the rear differential. It is easily identified by the two fill plugs facing the rear of the car and because it has two driveshafts coming out the left and right sides. As you can see, there are large square impressions in both drain plugs. A 1/2" drive ratchet just happens to fit in them perfectly. Put the stud of the ratchet in the hole and loosen the plugs (you might need to whack the ratchet with a hammer to get them loosened). These are removed using the standard "righty tighty, lefty loosy" method. Loosen both plugs, and then get a drain pan handy. Remove the top one to help air get in the differential, and then pull the bottom one out. It should drain out fairly easily. Make sure the car is either A) level or B) the rear end is pointing a bit downhill so that all the fluid drains.




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With both plugs out, you will notice the bottom one is slightly different from the top one- it actually has a magnet screwed to it. This is designed to keep metal particles away from the gears, but is also very useful in letting you know if your driving style is ruining the differential. A few particles of metal are fairly normal, but if it looks like 12 pounds of shrapnel, you are going to have major problems down the road.




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After a fashion, the old oil should be drained out- it will take awhile to drip off of the gears and run out. When it is done draining, put the bottom plug (the one with the magnet on it) back in, and tighten it down. What comes next can be messy- basically, you start filling the differential with the new fluid until it starts dribbling out the higher "fill" hole. I used a long piece of tubing and a funnel to make things a little less messy, though you can actually buy what amounts to a large syringe that is used specifically for things such as this. You fill the syringe up and press it out into the hole. At any rate, when the fluid backs up out of the fill hole, it's time to replace the fill plug and tighten it down.




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With both plugs back in, thoroughly clean off the differential and take the car out for a spin. You want it clean so that you can see if the plugs are leaking at all. Things should be fine, but it is best to find out on a short drive that you have a leak instead of halfway to work on Monday.




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