differentual oil change question

[sebgep]

i have a 91 gmc suburan and i want to do an oil change for it. i just don't know how. i found a drain plug but its not all the way at the buttom. i don't know if i should just take the back cover off. also, i don't know how to refill it. there is a hose that comes off about 3/4 of the way up and its capped off at the end.

 

also, i was wondering if the truck has a 3 speed auto with overdrive or a 4 speed with overdrive?

 

thanks in advance

[GM-Tech]

That's not a drain plug, that's the fill plug. The only way to drain it is to pull the cover or suck it out through the fill hole, which doesn't do that great a job.

 

There's no such thing as a 4 speed WITH overdrive. Well, back then anyway. Overdrive is the forth speed.

[sebgep]

ok thanks for your help.