im not sure where the drain plug is or if my blazer even has one on the rear diff. i had it on a lift and couldnt for the life of me find it. my question is, how would i go about changing the rear diff oil on my 2003 LS ???

 

https://blazerforum.com/forum/showthread.php?t=3366


<----------Rear of truck on passenger's side//Front of truck on passenger's side------------->


VERY good info in there.

 

thanks!!!!

 

ok i got the oil out, now how do i fill it back up? and how much?

 

Im guessing that you got the oil out by popping the rear cover off, or using a vacuum device to suck the fluid out the fill hole. I do my 01 every 30k and this is the procedure that i use. First i loosen all rear cover bolts and use a screw driver to gently seperate the cover from the seal. This will let the fluid drain out the bottom. Second, after all fluid is drained, i pop the cover off and clean the cover up with some brake cleaner to get the the metal around the magnet and stuff off. After all is cleaned up, i usually make my seal with gm black RTV stuff. You can buy seals from parts store for about 5 bucks usually. If you have a store nearby, it makes things a little easier. If you are going to make the seal yourself, i usually put a very light coat of sealant around the pumpkin itself , then a bead around the cover. After about 5 mins, i put the cover back on and evenly torque the diff bolts. I usually leave it sit overnight to insure sealant is good and dry. Last step is to fill your diff with fluid. I have a limited slip so if i use conventional gear oil, i need the LS additive or it will start hopping around turns. I usually use M1 75w90 LS gear oil and have not had a need to put the additive in yet. It takes right at two qts to fill it up. I believe the book calls to go to 1/2 inch below the fill hole but it is pretty much standard practice to fill to the fill hole then close her up. Hope this helps

 

Sorry, i didnt actually even answer your question. The fill hole is in the pic above, this is not a drain hole, unless you use a vacuum device or something to suck the fluid out. I usually just pull the back wheel off so i can reach up in there better. You can definately just lay under the truck and fill it. To fill it just take your 3/8ths extension and push it in the fill plug and take it off. Then just squirt the fluid in, however it is convient to do so. Usually you dont need anything special, just squirt the fluid in untill it is up the the bottom of that fill hole and plug it back up.

 

Did you read the link I provided in my first response? As I said, it has VERY good info.

 

Mine has a fitting with a rubber hose mounted where the fill hole should be. The hose runs up to a plastic anchor device in the chassis, behind the rear passenger wheel, which makes it totally inaccessible. Does this sound right, or am I looking at something else? It's a 2001 4x4 Blazer

 

If the firring and tube you are talking about are on the axle tube that is the rear diff. breather. The fill plug to refill the diff. is on the side of the diff. and if I remember correctly on the passengers side. It is a 3/8 square fitting.

 

Thanks DKSDAD, you're right, I was not looking in the right area. I found the fill plug and changed my leaky cover. Now it still leaks, a little worse than before. Are those cardboard gaskets that come with the cover any good, or should I buy a separate one? I tried tightening to the 28 ft-lb spec I read here and I started at the lower center screw and worked my way up, from side to side, ending with the top center screw. Still leaks. Tightened to 45 ft-lbs and it leaks less but still about a tablespoon over a 16 hour period of standing still.
I'm thinking I need a better gasket, and yes, I did my best to remove the old one and sand the surface down to good metal. There was a little rust on the outer edge, but the inner edge of the diff was clean and so I thought I could get a good seal.