: Rear Diff, how to change fluid



Patrick7997
06-12-08, 11:18 AM
Okay, this is a continuation of the "Front Diff and Transfer case" Thread.... Review that one to see some of my methodology, my pump, and some details...

http://i102.photobucket.com/albums/m118/Patrick7997/DSC00498.jpg

This is the Fill Plug on your Rear Diff. Looks rusty. This is going to be fun. This picture is looking from the passenger side rear tire, across the truck, towards the driver's side rear tire.

This is another square plug, so again, use your 3/8ths drive to remove that...

http://i102.photobucket.com/albums/m118/Patrick7997/DSC00500.jpg

Thru the magic of photography, the plug is out. What you missed were about 5 soakings with PB Blaster (all the wet stuff on the side of the diff), then some torching with a MAPP Gas torch, and then the bolt came out. Piece of cake, right?? Right...

Now, there is no drain plug on this case.

Now, this might not be "According to Hoyle", okay, so my apologies to real technicians out there... but I was shown this years ago by a friend, and if you're patient, and careful, it will work.

http://i102.photobucket.com/albums/m118/Patrick7997/DSC00501.jpg

This is the backside of that rear diff. That bowling-ball shaped rear cover plate is held on with bolts all the way around. The bottom 5 are visible in this photo.

If you loosen (do not remove) the bottom 7 bolts, and then very carefully and gently pry at the bottom, the case will open a little.. and fluid will drain.

You do not want to jamb the screwdriver way in there. You're just cracking it open a little... there's a gasket in there that you are trying not to damage.

http://i102.photobucket.com/albums/m118/Patrick7997/DSC00502.jpg

Like so. It was hard to get the picture, and do it at the same time, but a lot will come out when the case starts to open. Obviously, you will have your drain pan under there... and eventually, the case will be empty.

Then, retighten the 7 bolts you loosened, and wipe the excess off the diff, from the area where it was slobbering out of the case...

http://i102.photobucket.com/albums/m118/Patrick7997/DSC00504.jpg

Having done that, you now will set up your pump again, fill this case with 75w90 Mobil 1, and when full, replace the fill plug.

This is a big case. Took me almost 6 quarts to fill it.

And you're done!

DLE
06-12-08, 11:41 AM
Once again, awesome write up! This def helps us members out! Let this be a sticky! :thumbsup: :thumbsup:

hcvone
06-12-08, 01:24 PM
As said very nice, thanks. I pull the cover off completely to make sure the gasket area is clean, the new rear gaskets hold up very well.

chadande
03-24-09, 05:11 PM
hcvone, does the cover come off without having to move or loosen the crossmember and sway bar? It looks like a pretty tight fit.
Is there a magnet inside the cover or diff case? I was wondering if it accumlulates shavings anything like the front diff.

oldworld
03-24-09, 06:05 PM
Great write up.....VERY helpful to me.
THANKS

gscrazy1
07-12-12, 07:23 PM
could loosening the drum and prying it apart degrade the integrity of the gasket even if you did not hit it with the screw driver? I'm just wondering how well the gasket will seal afterwards, especially after oil has gotten onto it...

the cadillac man
07-12-12, 07:36 PM
could loosening the drum and prying it apart degrade the integrity of the gasket even if you did not hit it with the screw driver? I'm just wondering how well the gasket will seal afterwards, especially after oil has gotten onto it...

It is best if you do that to replace the seal to be on the safe side.

osure
07-12-12, 07:49 PM
as long as you dont tear it you are good I would but gasket seal on it. Or if in doubt replace