I just finished replacing my rear axle seals and I searched tirelessly for a thread specific to Colorado's and Canyons but came up with nothing. I realize it's an identical operation to that of an S-Series but I figured I would write up a quick how-to regardless.
I've borrowed the 355nation template for this how-to,
Replacing Rear Axle Seals
13mm socket - diff cover bolts
19mm socket - wheel nuts
Pry bar (slotted screwdriver will do) & small hammer
1/2 drive ratchet - Diff fill plug
Small magnetic pen, - removing c-clips
Block of wood - To install seals
Container to catch oil
- this really depends on if you are laying on the ground or using a hoist
Axle seals were $8 each
Oil was $13 a container
I started by first reading this how-to change your diff fluid by burns - How To: Change your rear dif fluid - Chevrolet Colorado & GMC Canyon Forum
^ It covers 50% of what you are about to do.
I then went out and purchased 2 containers of 75/90 gear oil and 2 rear axle seals. Only one of my seals needed replacing but this is one of those things if you are there do them both.
Start off by jacking up your truck and if you are like me and doing it in a driveway make sure you chalk your front wheels. Slide your stands underneath and remove the wheels. Loosen your lugs when the tires are still just touching the ground.
Remove drums, make sure to keep them on the side of the truck they came off of,
Inspect seals, mine was leaking the smallest amount but enough to fail a safety test,
Use your 13mm socket and get the cover off, make sure you catch pan is in place
Once the majority of the oil has drained out spin the axles until you can see the pinion shaft and pinion shaft lock screw, It's just on the top of the carrier in this picture. You have to put the truck in neutral to spin the axles,
Grab your 8mm wrench and another small one so that you can get some leverage,
You can't fully remove the pinion shaft lock screw but you can slide it out enough that you can remove the pinion shaft,
Once the pinion shaft is out just simply push in on the axles and they will slide in exposing the c-clips, you can just make it out in this picture, the bronze bit,
You may have to slide them around in order to pull them out.
This is where a pen magnet comes in real handy,
Once the c-clips are removed just simply pull the axle out. Again make sure to keep them on the respective side of the vehicle. I like to do one side at a time so that the same parts always go back on the same side.
Grab your pry-bar and hammer and knock the old seal out,
Make sure you have a rag handy as a bit of gear oil will come out,
Once it is removed then clean the area and remove any access grease. Grab your seal, hammer and piece of wood and tap it into place. Just be careful that it's going in evenly,
I like to pre-lube the seal with some gear oil,
Once you've done both sides everything gets cleaned and put back together. The axles slide right in and you reinstall the c-clips,
Inspect your pinion shaft, if it looks like this you may want to consider replacing it,
It's a good idea to inspect your pinion shaft lock screw. On s10s 7.5 diffs it just simply slides out but it's a bit more involved to remove it on these larger diffs. If this screw breaks when you are trying to remove it you are in for a **** of a lot more work then you anticipated. If it looks like this replace it
So pinion shaft and lock screw reinstalled,
Clean your gasket surfaces,
Very little metal shavings on my pick up,
Clean your gasket, photo courtesy of burns. If your gasket is ruined you can just use rtv instead.
Cover bolted back on,
Fill it back up with gear oil, for those that don't know just keep pouring it in until it starts to come out. Once this is done check for leaks.
Reinstall drums. I like to put anti-seize on the mating surface and lugs. Chances are I will have them off again so why not make it easier for yourself.
Wheels backs on and down the road you go,
Just remember take your time and do it right.
Hope this helps a few people out there.