Rear Differential Fluid Change

[SJR]

After my first 500 miles of towing I will be somewhere in north central Kansas. I will do my own fluid change on the rear end. Any specifics on tools and or technique would be appreciated.
Thanks for any help.
SJR smile.gif

[Reno DMAX]

SJR,

For your rear differential fluid change you'll need:

• Oil Drain Pan
• 3/8" Socket Wrench
• Metric Sockets
• 4 quarts of Synthetic 75W 90 GL5 rated gear oil (Redline, Amsoil, Mobil 1)

Note: If you plan on doing extensive heavy towing, the recommended weight gear oil is 75W 140

Procedure
-----------

Place the drain pan under the differential, remove the top plug then the bottom plug and watch it drain (you might want to hold your nose at this point).

While the gear oil is draining, thoroughly clean the drain and fill plugs. Install the bottom plug first (very important). Fill with 4 quarts of Synthetic GL5 rated gear oil. (75w 90 or 75W 140). Torque fill and drain plugs to 24 lb. ft.

For filling, some people have recommended a cheap gear oil pump. I tried one but it took forever. Others have recommended using a suction pump. I bought a funnel (Wal-mart) that had a clear plastic hose connected to the bottom. I bought a longer hose and was able to add the thick gear oil to the funnel while standing up beside my truck.

Drive it making several left and then right turns to disperse the gear oil.

[ 06-25-2002: Message edited by: Reno DMAX ]</p>

[SJR]

Thanks Reno
What metric sockets will I need? Does the 3/8 socket wrench fit the plugs?
Thanks
SJR smile.gif

[SoCalDMAX]

Here ya go,

Bring the following:
1. A container capable of holding 4qts that fits under the diff.
2. A 3/8" ratchet and a socket to fit the oil fill plug.
3. 4 qts of your favorite approved synthetic gear lube and a little funnel or tube to help get it in.

Remove the spare tire to make it super easy. The drain plug on the bottom has a square hole in it, the ratchet will fit right into the hole. After draining, clean and replace drain plug, remove fill plug and pour in 4qts of fluid.

Reinstall spare and find a parking lot to do figure 8s in to distribute the lube and you're done.

Don't be alarmed if you see a small amount of metal shavings or even a small chunk of metal, it's normal. At least you removed it so that it won't wear the gears further.

Have fun on your trip!

Regards, Steve

[86gmc]

15mm socket or box end wrenck size on top drain plug. changed mine yesterday at 960 miles some metal filings on bottom plug magnet. 4 qts of Amsoil 75w-90 brought mine up to about 1/4 inch below threads on top plug. The Walmart clear tube that screws on to quart containers of oil was all I used to get oil in to differential. It's easy to do and front diffenntial also has a drain plug.

[CSDMAX]

Reno DMAX and SoCalDMAX,
It sure makes it a lot easier when you can find the info here on TDP rather than fumble through the manual and then figure out which lube, tools, etc. I changed the oil this evening and it's a good thing I checked, the diff only had 3+ quarts in it. :mad: Followed your guidelines and took 4 quarts no problem. Thanks for the posted info.
Don

[SJR]

Thanks for all the help. I have all the tools lined up and in a couple of days we will head out.

Do I understand that any synthetic GL-5 rated 75-140W will work (e.g. Mobil, Penzoil etc.) and keep me from buying the expensive GM stuff?
Thanks again,
SJR

[TXMAX]

Since you're going to be on the road and probably don't want to carry an oil drain pan, try this instead.
Get cardboard box and a heavy guage plastic bags that will hold at least the expected 4 Qts. You can fold the box for easy storage then when you need to use it open it up and line the box with the bag (double up if you are concerned about tears). Drain rear diff fluid, tie off bag (leave it in the box) take to auto parts store and dispose of properly. This can work for almost any fluid changes and takes up no room.

Abe

[Turbo Al]

SJR: I changed my diff oil half way through my holidays as well. I just found a drainage ditch & backed the rear end of the truck over it, I did let it cool down for an hour after towing. Had lots of room to work on it. I drained the oil into a plastic milk jug (paper funnel) then just poured it back into the empty oil containers -- the one's left over from filling the diff.
Turbo Al

[Idle_Chatter]

It's really pretty easy to do, once you know that the drain plug is 3/8" square (just stick a 3/8" ratchet handle or extension in there) and that the fill plug is 15mm ( I fooled around for a while trying to test fit that!) One thing that got me was the "top" plug is not on the TOP! I was crawling all around and poking and looking at the top of the punkin! The "top" or fill plug is the plug on the back (nearly 3/4 of the way down) of the diff cover (Duh!) Mine was "weeping" even after cleaning and retorquing it there's still a "streak" down the cover. The GM factory fill "grape juice" does have an *awful* smell to it.