Hey Scotty! Long time fan! I recently acquired a 2004 Grand Marquis LS premium 85,000 mi for $2,800. I'm working on it making it really nice and can post pictures when I'm done. Anyhow I recently drop the diff cover wire brushed sanded primed multiple coats painted multiple coats whole rear axle and frame area and differential (NY car). So anyway I filled up the differential on an incline and about 2.9 quarts went in when the book capacity is 2.4 quarts. Is it okay to leave the extra half a quart in there? Or Do you think I should drain out the excess?
THANKS!
i do see a vent tube sticking out of the top of one the the half shaft areas. One may think any pressure building would be relived that way?
Yes, that's what it's for. You don't want to go through water deep enough to submerge that. Many 4WD vehicles, especially those designed for off-road use, use a hose to extend the vent to a higher level to avoid water intrusion when fording streams.
it did have a tube that went up the side of the coil spring
They'll go even higher up on off-road vehicles.
@chaoscraig - to clarify, as @imperator said, that vent is for relieving AIR pressure to protect the seals. It never occured to me that you might think it was for excess oil. It is most definitely not. The only place excess oil is going to go is through the seals at the ends of the axle tubes and spray all over the brakes.
The excess can find its way out to the wheel bearing oil seals and overwhelm them, getting lube all over the rear brakes. I found this out the hard way after similarly changing the rear diff oil in my '99 Cherokee with the rear end jacked up.
With the car level, open up the differential fill plug and let it drain until the oil is level with the lower threads in the opening.
Differential fluid expands as the differential gets hot. I didn't even know you could squeeze an extra .5 quarts into a 2.4 quart differential. Find a flat surface and drain out the excess. The differential is splash lubricated. When enough pours out, and you're certain the vehicle is level, stick a finger into the differential and feel the level. If the level is good, replace the plug.
should drain out the excess?
You should set the correct level.
the oil level in there is carefully tuned to optimize splash lubrication to keep the differential cool, and the bearings (which aren't submerged) lubricated. Too much oil can cause aeration.
2.9 quarts went in when the book capacity is 2.4 quarts.
Ignore the book numbers. Those are just to get you close. Axles have fill procedure. It's usually right up to the fill hole, or a few millimeters below it.
Wow thanks for all the prompt replies every one. i do see a vent tube sticking out of the top of one the the half shaft areas. One may think any pressure building would be relived that way?
The vent tube relieves AIR pressure when the axle heats up, so that the axle doesn't start pushing the seals and fluid out.
But it doesn't drain off excess fluid, and it doesn't help with overfilled axles that foam up and don't lubricate properly.
Ah, I read his comment as though he meant air pressure since that what comes to mind when I see those vents.
maybe he hasn't seen "aeration" before. It still happens in vented housings.
https://www.youtube.com/watch?v=9-yG3D3JBRs&t=335s
Don't flush the transmission.
So should i add more now?
book said 2.4 qts i already put in 2.9 hmmmmm
I thought I already answered this.
So, again .... ignore how many quarts the book says. It doesn't really matter ... same as an engine. Same as a transmission.
You need to follow the fill procedure in the service manual. It will specify an exact level you should fill up to.
And remove fill plug and nothing came out???!?!?!
stick a tool through the hole and measure how far down from the bottom lip of the fill hole the oil level is.
those 'L' shaped allen keys work well for this.
copy
Update, i brought the vehicle more level. And remove fill plug and nothing came out???!?!?!
So should i add more now?
book said 2.4 qts i already put in 2.9 hmmmmm
Update, i brought the vehicle more level. And remove fill plug and nothing came out???!?!?!
So should i add more now?
book said 2.4 qts i already put in 2.9
It's just as @mmj stated, you fill it until the fluid level is almost to the level of the fill hole. A slightly smaller amount/less won't hurt. Always check the fluid when the car is level to ensure accuracy.
Thanks i finally got the level. So onto transmissions service. Pan drop filter drain refill?
orr flush? i know scotty is not a fan of flush.
Thoughts?