how to fill differentials precisely?

apollo18 · October 14, 2017

hey guys! i think my front diff calls for 1.8 quart and my rear is 2.75. does that mean I just do 2 quarts front and 3 at back? or should i be super precise? i believe its an eaton g80 awd truck

thanks

Arth · October 15, 2017

Just did this in my Avalanche. Filled both until fluid started to slowly leak out. Also did this for the transfer case.

I'm sure there some more precise way to do it but I did this about 6000 miles ago and no issues thus far.

apollo18 · October 15, 2017

makes sense! cuz some people say dont overfill but like how am i supposed to measure out 1.8 quarts or 2.75 lol

txab · October 15, 2017

Sometimes specs are given the full point is a certain measurement below the threads. Easy to check with a bent pipe cleaner, piece of wire etc....

reardiff · October 15, 2017

I've used an Allen wrench which works great for this purpose.

txab · October 15, 2017

21 hours ago, reardiff said:

I've used an Allen wrench which works great for this purpose.

Yes another good tool

reardiff · October 16, 2017

And it's something every one has with no need to bend, buy or break anything. Just wipe it off and toss back in the tool box.

sdeeter19555 · October 16, 2017

Sometimes specs are given the full point is a certain measurement below the threads. Easy to check with a bent pipe cleaner, piece of wire etc....

I've always wondered how this works when the center chunk is asymmetrical...if you do nothing but turn a wheel 90 degrees, the center chunk may or may not have an opening positioned in the fluid that could change the volume volume...think of the window through which you access the spider gears. Close enough I guess?

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newdude · October 16, 2017

Per GM, fluid level is at the threads of the fill plug or up to 0.4 inches below them. So spec is 0.0-0.4 inches from the fill threads. Correct level is read on the level ground or a drive on 4 post lift, as the axle is at the proper fluid checking angle. Also, I'd drive it, get the fluid warmed, then let it sit for some time before draining so as much of the lube from the axle shaft housings drain back into the diff. Once you fill it, I would repeat that again to just double check the level.

Cowpie · November 1, 2017

My manuals on my 2013 1500 and my 2015 2500 says fill to bottom of fill plug on front diff, rear diff, and xfer. Doesn't get any simpler than that. The same procedure I have used for better part of 50 years. I just drain and fill. No extra steps. Have never lost a xfer or diff in 50 years on everything from personal cars on up thru commercial trucks.

Not sure one can overfill. They may pump in too much, but let the excess drain out before reinstalling the fill plug.