OK. Finally changed the oil in my differential. I changed the ORIGINAL FACTORY OIL
Milieage is 111,837
The manual calls for
SAE 75W-90 Synthetic Axle lube GM part # 78261 or meeting GM spec 9986115.
I created a thread on the appropriate fluid to use- and the confusion that GM SPEC causes. In the end- after viewing documents online- AMSOIL 75W-90 Severe Gear oil is a perfect replacement. People have said Mobil 1 is ok to use- but I emailed Mobil 1 and they said they did not meet the spec- and to procure the oil from dealer. So its up to you if you want Mobil 1. Dealer oil, or AMSOIL. (or other stuff of your choosing- hopefully its meets requirements).
So the parts needed are shown in the picture + You will ALSO need a 3/4 extension, a 3/4 ratchet and a breaker bar (if youre weak like me).
![Image]()
I went ahead and removed the rear tire- for several purposes. To check its condition, to refille with air, to operate the lowering mechanism, and to clean the tire. It also gives you space to work on the rear end.
![Image]()
on my 03, I have a drain hole. shown here.
![Image]()
Here is the location of the refill hole
NOTE!!!!!, before you drain the oil, use your 1/2 inch extension and ratchet to try to remove the refill hole. It does no good to drain, if you cant remove the refill hole. Be careful using the extension- try to hold it in place as tight as possible. the little ball bearing on the extension may keep the extension from fitting in the little square- if youre not careful youll round the edges of the square. I used the breaker bar to help me get leverage.
![Image]()
I was a little surprissed when I removed the refill hole- as it started to spill oil thru here. the level was high enough.....
I placed the drain pan and let it drain a bit.
I then proceeded to remove the drain plug and let it drain out.
![Image]()
Once its drained out- you can refill.
Since my rear end had 111,837 miles on it, I wanted to see what condition the gears were in. so using a 13mm socket I started to remove the bolts.
You will need the 3/4 socket extension to clear the metal bar that partially blocks 1 bolt- OR use a wrench.
heres my cover- and views of the insides....
![Image]()
![Image]()
![Image]()
![Image]()
![Image]()
I did not buy a gasket- as Id seen on here that the gasket was rubber and most likey reusable. (and hard to get at auto parts stores- and if they have it- its wrong- as per members on here).
I cleaned the mounting surface
![Image]()
I then cleaned the cover.
![Image]()
then I cleaned the gasket. still in very good shape
![Image]()
I then put everything back toghether again. I didtn use a torque wrench. I tighethened the bolts to about what they felt like when I removed them. they werent that tight (never had a leak). I put all bolts in and tightened them like on the tires. across from each other...
once it was all back toghether again. it was time to refill.
The contraption I Have in the picture I had to cut the hose to get the bottle upside down and get it to drain. it was a bit messy- and tedious.
Learn from me- and use a hand pump.
(I had one- but dad had cleaned it out with gas- and I didnt want to introduce gas into the amsoil). so do yourself a favor and buy a little pump.
it will make it easier....
2 quarts is all youll need. it brought the level to a bit below the fill hole.
(not sure why it had more when I removed the fill hole 1st time).
here is what settled on the bottom when I removed the oil. the black spots were not metal....... they were sort of like plastic. cause I could crumple it in my finger. Im not sure if they fell in when I was undoing the drain holes.
you can see the super fine metal particles.
![Image]()
here it is all put back toghether again..... I went ahead and cleaned the cross bar- since some oil falls on it.
![Image]()
I was surprissed what I didnt find......
I DID NOT find any large metal flakes. chunks etc....
I found less fine metal particles than I thought Id find.
Could be they were suspended in the oil. (magnet would have helped).
But in close inspection the rear end gears looks exceptionally good to me.
Milieage is 111,837
The manual calls for
SAE 75W-90 Synthetic Axle lube GM part # 78261 or meeting GM spec 9986115.
I created a thread on the appropriate fluid to use- and the confusion that GM SPEC causes. In the end- after viewing documents online- AMSOIL 75W-90 Severe Gear oil is a perfect replacement. People have said Mobil 1 is ok to use- but I emailed Mobil 1 and they said they did not meet the spec- and to procure the oil from dealer. So its up to you if you want Mobil 1. Dealer oil, or AMSOIL. (or other stuff of your choosing- hopefully its meets requirements).
So the parts needed are shown in the picture + You will ALSO need a 3/4 extension, a 3/4 ratchet and a breaker bar (if youre weak like me).
I went ahead and removed the rear tire- for several purposes. To check its condition, to refille with air, to operate the lowering mechanism, and to clean the tire. It also gives you space to work on the rear end.
on my 03, I have a drain hole. shown here.
Here is the location of the refill hole
NOTE!!!!!, before you drain the oil, use your 1/2 inch extension and ratchet to try to remove the refill hole. It does no good to drain, if you cant remove the refill hole. Be careful using the extension- try to hold it in place as tight as possible. the little ball bearing on the extension may keep the extension from fitting in the little square- if youre not careful youll round the edges of the square. I used the breaker bar to help me get leverage.
I was a little surprissed when I removed the refill hole- as it started to spill oil thru here. the level was high enough.....
I placed the drain pan and let it drain a bit.
I then proceeded to remove the drain plug and let it drain out.
Once its drained out- you can refill.
Since my rear end had 111,837 miles on it, I wanted to see what condition the gears were in. so using a 13mm socket I started to remove the bolts.
You will need the 3/4 socket extension to clear the metal bar that partially blocks 1 bolt- OR use a wrench.
heres my cover- and views of the insides....
I did not buy a gasket- as Id seen on here that the gasket was rubber and most likey reusable. (and hard to get at auto parts stores- and if they have it- its wrong- as per members on here).
I cleaned the mounting surface
I then cleaned the cover.
then I cleaned the gasket. still in very good shape
I then put everything back toghether again. I didtn use a torque wrench. I tighethened the bolts to about what they felt like when I removed them. they werent that tight (never had a leak). I put all bolts in and tightened them like on the tires. across from each other...
once it was all back toghether again. it was time to refill.
The contraption I Have in the picture I had to cut the hose to get the bottle upside down and get it to drain. it was a bit messy- and tedious.
Learn from me- and use a hand pump.
(I had one- but dad had cleaned it out with gas- and I didnt want to introduce gas into the amsoil). so do yourself a favor and buy a little pump.
it will make it easier....
2 quarts is all youll need. it brought the level to a bit below the fill hole.
(not sure why it had more when I removed the fill hole 1st time).
here is what settled on the bottom when I removed the oil. the black spots were not metal....... they were sort of like plastic. cause I could crumple it in my finger. Im not sure if they fell in when I was undoing the drain holes.
you can see the super fine metal particles.
here it is all put back toghether again..... I went ahead and cleaned the cross bar- since some oil falls on it.
I was surprissed what I didnt find......
I DID NOT find any large metal flakes. chunks etc....
I found less fine metal particles than I thought Id find.
Could be they were suspended in the oil. (magnet would have helped).
But in close inspection the rear end gears looks exceptionally good to me.
