Overfilled diff?

Status
Not open for further replies.
Joined
Nov 23, 2016
Messages
1,732
Location
WI
Did the diffs on my Liberty, filled the front till it ran out the fill plug and let it drain out of the fill, so the level is probably about even with the bottom of the fill plug. I was checking the manual today for a light bulb part # and noticed for the diffs it said spec is 1/2" below the fill hole. Should I suck a little out or is it okay to leave as is? Don't want to blow any seals out.

Thanks!
 
There is a breather on the diff. I'm overfilled on the Jeep, but have no idea by how much because my pinion angle is way off. No issues, additional drag is not a concern on that rig.
 
Leave it alone ......
for there isn't any (engine) crank to 'hit' the gear oil.
The gears and bearings will thank you for that.
The proof of the pudding is in the eating ....., by checking and ascertaining it's cool operating temperature.
 
Did you perform this service on a slightly angled driveway? If so, it's possible you got it exactly right anyway.
 
Most or all of the diffs that I have serviced called the unit full when the gear oil drizzled out of the fill hole.
However, they also stated that if you can feel/get oil on your finger(when inserting in the hole) than that's good enough.
 
If it is level with the lowest part of the threads of the fill hole it is fine. In fact that is how I was taught to fill them in school. It can be there or up to a 1/4" below with no worries.
 
I'm anal about that stuff, I would remove some.
Does it really matter I don't know.
I'm sure it's cold level not hot level.
My Chevy 10 bolt rear ends have that same call out.
Why in the world would they not place a drain plug in a location so you could fill to top of the hole.
It's hard to get it 1/2 to 5/8 below the fill hole on mine.
I use a bent pappaer clip to measure mine.
 
Originally Posted by 01rangerxl
I don't do the x amount below plug thing...fill it until it drips out.


Done this way for years … front and rear on two sets of ramps to be level …
 
I fill the diffs until it flows out on the Volvo 240 Dana 30 axles. This is what the Bentley 240 manual and my mechanic suggest. There's never been an issue.
 
Last edited:
Originally Posted by tblt44
I'm anal about that stuff, I would remove some.
Does it really matter I don't know.
I'm sure it's cold level not hot level.
My Chevy 10 bolt rear ends have that same call out.
Why in the world would they not place a drain plug in a location so you could fill to top of the hole.
It's hard to get it 1/2 to 5/8 below the fill hole on mine.
I use a bent pappaer clip to measure mine.

get therapy....lol
 
So long as the diff fluid does not expand into the breather tube and block off air, you're ok. If it does, thats when you can damage a seal. I know from experience. Had a diff breather fall down under the truck, causing the breather tube to suck in water and overfill. Best way to be sure is pull the fill plug after a drive when the fluid is hot and expanded. that will give you pretty close to the specified inch below the fill
 
Always good advice to ignore the owner's manual. Did Jeep put that in there just to cause owners a bit of grief getting it right, if level with the fill hole is best practice why would Jeep not just spec it?

Everyone who fills til it spills, what does your manual say? Maybe that's correct for your vehicle.
 
Never been an issue for me in decades of doing it full … isn't there is another risk to under fill ?
Some of my aftermarket covers had a weep hole for fill level …

My owners manual has no mention of diffs changes
 
Last edited:
How do you reliably fill it 1/2" below the fill hole ?

Do they mean 1/2" below the center of the hole ? Do they mean 1/2" below the bottom of the hole ?
 
Originally Posted by AZjeff


Everyone who fills til it spills, what does your manual say? Maybe that's correct for your vehicle.


Mine states to fill to some level below the hole, and I've never done that.

My owner's manual also says the fluid is good for 150k mile intervals, which is probably true, but I ignore that recommendation too.
 
Status
Not open for further replies.
Back
Top