Be Patient Filling Your DIffs

[Gebo]

Most of you probably know this but my observation may help one or two DIYer's. I was refilling my rear diff that is supposed to take
2.5-3 qts of gear oil (I drained out about 2.75 qts of old fluid).

Well, I started filling it up and at 1.75 qts the gear oil was trickling out of the fill hole. What the heck???? I went inside to finish my
popcorn from Saturday night and came out about 15 minutes later and got 2.5 qts in before it started to trickle out the fill hole. Went back in and watched the first episode of Yellowstone and came back out and got 3 qts in until it started to trickle out the fill hole.

Yes, it was about 40 degrees outside but the gear oil was about 60 based on it being in my garage.

I wonder how under filled all my other diffs are?

You gotta be patient when filling diffs with gear oil. My observation...

 

[ctechbob]

If the factory level is set to be just above the axle tubes, this makes sense since the oil may have to work its way through the bearings and out the tubes if that's how they designed it. Makes sense it might take a little longer with thick/cold oil.

Never paid attention to where the level is on my Ranger, don't think it would be above the tubes since it takes under 2qts.

 

[Warstud]

Check it again after driving it around.

 

[Gebo]

Check it again after driving it around.

Valid point.

 

[Graham Piccinini]

I knew someone who claimed to overfill his diff once. He said that once he got up to highway speed while towing - the fluid expanded a bit from heat and blew his axle seals out. Whether this was the cause or not - I do not know and can't verify anymore. But I do know he had to replace that rear diff in the truck afterwards.

 

[Lubener]

You may want to check that your diff's vent is clear. That may contribute to the gear oil slowly chugging as you attempt to fill the differential. You should never have to recheck the level after a test drive to add more.. I never had to do that.

That's why I do this kind of service in the summer time when the oil is not nearing being as molasses. I get the whole process done in less than an hour.

 

[DejaVue]

I knew someone who claimed to overfill his diff once. He said that once he got up to highway speed while towing - the fluid expanded a bit from heat and blew his axle seals out. Whether this was the cause or not - I do not know and can't verify anymore. But I do know he had to replace that rear diff in the truck afterwards.

One that comes to mind is AWD Volvos the dealer manual says fill it and then remove 100mL.

 

[HemiBenny]

Most of you probably know this but my observation may help one or two DIYer's. I was refilling my rear diff that is supposed to take
2.5-3 qts of gear oil (I drained out about 2.75 qts of old fluid).

Well, I started filling it up and at 1.75 qts the gear oil was trickling out of the fill hole.

got 2.5 qts in before it started to trickle out the fill hole.

got 3 qts in before it started to trickle out the fill hole

So 7.25 quarts later, minus the little bit that trickled out, you filled your diff that has a 2.5-3 quart capacity?

Edit- ok, I’m awake now, it took a few minutes and a cup of coffee before my comprehension skills started working this morning. I was reading it as how much you put in each time, not the total amount that you had got to at each attempt.
Note to self, wake up, have coffee, and turn on my brain before commenting on BITOG.

 

[Blueshound]

Most of you probably know this but my observation may help one or two DIYer's. I was refilling my rear diff that is supposed to take
2.5-3 qts of gear oil (I drained out about 2.75 qts of old fluid).

Well, I started filling it up and at 1.75 qts the gear oil was trickling out of the fill hole. What the heck???? I went inside to finish my
popcorn from Saturday night and came out about 15 minutes later and got 2.5 qts in before it started to trickle out the fill hole. Went back in and watched the first episode of Yellowstone and came back out and got 3 qts in until it started to trickle out the fill hole.

Yes, it was about 40 degrees outside but the gear oil was about 60 based on it being in my garage.

I wonder how under filled all my other diffs are?

You gotta be patient when filling diffs with gear oil. My observation...

Thanks, this is a helpful observation. Especially since one often wishes to "be done" with this task as soon as possible.

 

[Gebo]

In case you aren't aware, this is the rear end the burnt up due to lack of gear oil per East Coast Gear Supply. My mechanic
did not properly fill it after replacing the rear cover. Now, I think I know why. He filled till it drained out which was about 1.75 qts.

I was changing the gear oil after ECGS's recommended 500 mile break in period. Got up this morning, slapped on the surgical
gloves, went out in the garage and loosened the hand tightened 24 mm fill plug. I was tickled to see the gear oil ever so slightly
trickle down into my catch can. Absolutely perfect IMHO.

I'm gonna head out to Bojangles for a biscuit and mix all that liquid gold up.

 

[PontiacHO]

I recall our Corvette tech at the Chevy dealer refilling the diff on a 70s era C3 Corvette. He was squeezing the bottle so hard (in a hurry) that he blew the plastic filler tube off the bottle and into the diff. Do you know what it takes to get the diff cover off of a C3 Corvette? Several hours of free labor on his part…..

 

[D60]

I recall our Corvette tech at the Chevy dealer refilling the diff on a 70s era C3 Corvette. He was squeezing the bottle so hard (in a hurry) that he blew the plastic filler tube off the bottle and into the diff. Do you know what it takes to get the diff cover off of a C3 Corvette? Several hours of free labor on his part…..

I did this with just the little nipple cap in a TTB front diff once. I was "testing" positioning of the bottle (college days when I didn't own any pumps) and the cap slipped off into the diff.

Truly opening up a TTB diff is as much or more work than any other IFS truck today, but I left the cap anyway. Years later I found it and it had just wedged itself between the ring gear and carrier.

Come to think of it, most fill holes are ~1/2" NPT so you couldn't fit the entire bottle cap if you wanted to. C3's must use a unique fill setup. Or, if he just shot a filler tube in there it could be ignored on most applications (it'll just extrude if it does anything at all) but I wouldn't risk on an "exotic" like a Vette and I'd only consider leaving it on my own personal vehicles -- not a customer's.

 

[PontiacHO]

He actually drove the Corvette around the block to ensure his initial repair (u joints in the axles) was ok before dropping that transverse rear spring assembly to remove the rear cover. Good thing he did because the fill tube got ground up in the ring and pinion. Quite a bit of clean up took place to ensure no more tube material in the pinion and carrier bearings. I can still visualize him being so frustrated even after 40+ years have past.

 

[gman2304]

After changing my diff oil 2 years and 20,000 miles ago, my ocd is telling me to check my diff oil…..

 

[Gebo]

After changing my diff oil 2 years and 20,000 miles ago, my ocd is telling me to check my diff oil…..

It’s on my list as well BUT it’s only 34 degrees here. Yikes!

Back to 59 tomorrow. 61 Wednesday

I’m gonna wait and have a small victory over my OCD.

 

[01rangerxl]

I'm gonna head out to Bojangles for a biscuit and mix all that liquid gold up.

SIR IT'S GOING TO BE A 30 MINUTE WAIT ON BISCUIT, CAN YOU PULL AHEAD PLEASE?

 

[Gebo]

SIR IT'S GOING TO BE A 30 MINUTE WAIT ON BISCUIT, CAN YOU PULL AHEAD PLEASE?

For a Bojangles biscuit, no problem.

 

[Rand]

This is coming up on the 2020 ram.. and about a year away for the forester.
Pondering HPL or using the valvoline squeeze bags.

 

[Hall]

I knew someone who claimed to overfill his diff once. He said that once he got up to highway speed while towing - the fluid expanded a bit from heat and blew his axle seals out. Whether this was the cause or not - I do not know and can't verify anymore. But I do know he had to replace that rear diff in the truck afterwards.

I don't think you're supposed to get (too much) gear oil into the axle tubes. They do have seals but I suppose that's more cases where the gear oil gets splashed or spilled into the tubes (during hard turns, for instance). Look at the position of the fill port on diffs. It's always just below the centerline of the axles, isn't it ?

 

[BHopkins]

Wow. That's strange. I've never experienced anything like that when filling a diff. I've always go about the same amount in as what came out, and without any waiting.

I will say, I use a different method than most, for filling a diff. I truly despise the mess that is usually associate with squeezing the bottles or bags. So I use a modified 1 gallon garden sprayer. I have a curved hose end that hangs in the diff fill hole, open the ball valve that I installed on the hose, and let it flow. When it overflows, I compare the amount out to the specification, and it is always right there.

Since the amount in always matches the spec, I've never thought of letting it set for a while and double checking the level. Just for kicks and giggles, I'll have to try that next time.