Change Rear Diff Fluid

[fflynn]

I never really sized this up... but by just taking a quick look... I do not see bolts that look like a fill or drain plug... All the bolts look like regular plate bolts.

 

Where would the plugs be located for filling and draining rear diff fluid on a 99 GMC Sierra?

 

Thanks

[MattDewalt]

I just had mine apart yesterday. Drain plug is on the bottom of the rear, fill plug is on the right side of the rear just below a tag that says something like "75W90 synthetic...fill to 15-40mm below fill plug opening". They are not a bolt head type plug. they almost sit flush with the surface of the housing and have a square receseed hole in them. You simply insert a 3/8 drive ratchet into the square hole and start turning to remove.

[99silveradoz71]

a marine style pump may help get the fluid in as well.

[blue2kzr2]

I had no trouble getting fluid into the 8.5" rear in my S-10, just took a little squeezing of the bottle. I can't imagine the full-size would be HARDER than mine.