[Legal Bill]

that is actually a portion of a rear diff service.
you need to inspect the ring gear wear pattern, and look for metal in the bottom of the case.
I mean its good to pu fresh lube in there, but, youre only doing half the job.
Also 4 qts of quality lube is about $100. So not sure how youre going to do the job for less.

I'm talking about the cost of the pump.

 

[Legal Bill]

You can get a cheap fluid transfer pump at harbor freight or another parts store and do that. I did this with a lawnmower gas tank. If yours is really low mileage its likely ok to do. if its 100k or more and never been done you would be wise to do the cover and inspection. Its a $1500+ bill for a shop to completely rebuild the rear depending on the cause.

This is the one I got. Worked ok for what I have used it for thus far. I think it would be nice to have an electric or air one like posted above though.
View attachment 968043

I've used those in the past. They are best for water an other less viscous fluids. They don't move gear lube very quickly and the hoses can blow out making a worse mess than opening the diff cover.

 

[Legal Bill]

Hey, I get it, at least you are trying to do something, although most of us would say you should just take the cover off. But, with that said, here's a pump that should work for that:

Amazon.com: Mityvac 7201 Manual Fluid Evacuator Plus with 2.3 Gallon Reservoir; Evacuates or Dispenses Fluids with Push Button; Evacuate Through The Dipstick Tube : Mityvac: Automotive

Buy Mityvac 7201 Manual Fluid Evacuator Plus with 2.3 Gallon Reservoir; Evacuates or Dispenses Fluids with Push Button; Evacuate Through The Dipstick Tube: Fluid Evacuators - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

They make a few kinds like this.

Thanks. That is a leading candidate. I was hoping for some first hand experience from those with GM trucks. I guess people mostly pull off the cover.

 

[Legal Bill]

You're kidding, right?

A dozen bolts and a gasket. (I'm old school.)
30 minute job, tops....and you don't even have to jack it up.

No, I'm not.

Old school was opening up the drain plug at the bottom of the diff.

 

[Legal Bill]

Rear diff, w where the hole is and what' inside. using a hose to suck stuff out is unlikely to do a good job.

I would suggest, if you want to spend money, get a rear cover for the diff, and perhaps a transmission pan, both with drain plugs, so you only have to remove the cover once...

Not a bad idea. I didn't know they existed, but it makes sense that someone saw an opportunity. I'll look into that.

 

[Legal Bill]

To each their own, but why not just do it right by removing the cover, cleaning everything and so on?

I'm not sure what's right about one way or another. The owners manual doesn't even list rear differential (or rear axle) fluid on the maintenance schedule, and the schedule goes out to 150,000 miles. In fact, I just double checked the manual and the index to make sure. No mention of changing the rear axle fluid, just a section on how to check the level and what to add if you need to top it off. I just figured that as long as I was doing a fluid change I'd change the rear diff fluid. I bought the truck with 100,000 miles from the original owner. He had all the service done at the dealership, but doesn't have any receipts and can't recall when any fluids were last changed, except the oil.

 

[Legal Bill]

Take loose and remove the fill plug first, especially if you haven't serviced the housing in a while (or ever)...If that fill plug is stuck, seized or the square-drive head is stripped, at least you know before taking the cover off then having to wait around for a structural cover w/drain and fill plugs to arrive.

Otherwise, take the cover off, clean everything and do a visual inspection. Then check backlash...If backlash is excessive, rebuild the diff and replace your axle bearings and seals at that time.

Thanks for the advice. The rear axle seems fine. I was just going to change the fluid since I was going through all the lubricants. In your experience, do you find differentials that need to be rebuilt before they exhibit any signs of wear while driving the truck? That could push me to open it up and at least look.

 

[Legal Bill]

True. I guess I should've wrote "the old-school way" or something to that extent. But with removing the cover you can make sure you get everything out as well as clean and inspect everything. To me, that is the "right way". But like I also said, to each their own.

In my old school the differentials had drain plugs. I've been swinging wrenches since the 60s, but I was not a Chevy guy. Maybe they have had this design for a long time and I just never saw it.

 

[Legal Bill]

I would 100% take the cover off. It's the ONLY way you can thoroughly check and clean the innards. I did mine not long ago.
View attachment 968057
[/QUOT

I think some HD trucks still have drain plugs, just not the 1500. Pretty sure there are aftermarket covers also for the 1500 trucks if you want one.

I Just looked at a few of the aluminum covers with drain plugs on line. Mighty pricey!

 

[Legal Bill]

My '04 has a drain plug in the base of the rear diff, I think my '12 also does, they are both 3500's... I don't think the 1500's got them after the early GMT800 models.

That is correct. The 1500s don't have the drain plug AND the owners manual does not list rear axle fluid change as a maintenance item on their 150,000 mile maintenance schedule.

 

[Legal Bill]

You can get a cheap fluid transfer pump at harbor freight or another parts store and do that. I did this with a lawnmower gas tank. If yours is really low mileage its likely ok to do. if its 100k or more and never been done you would be wise to do the cover and inspection. Its a $1500+ bill for a shop to completely rebuild the rear depending on the cause.

This is the one I got. Worked ok for what I have used it for thus far. I think it would be nice to have an electric or air one like posted above though.
View attachment 968043

So in the interest of full disclosure and bringing any followers up to date, after a lot of research and considering my needs I ended up buying exactly this pump and it did a great job emptying out the diff without leaking a drop. The amount removed seemed to be exactly the capacity discussed in other threads on this site. After I was finished I cleaned the unit up and put it n a plastic bag for the next time. I guess I saved about $70 buying this cheapie. Thanks for posting!