I now own a 3/4" square drive adapter. A tale of rear diff fluid change.

[MrPulldown]

Since a lot of the service history of our EX is unknown to me, I have been going through and bring her maintenance up to speed. Thanks to EF I learned that I should be using the heavy weight stuff (145)in the rear diff instead of the thinner (90) weight stuff. I also learned to look up the rear diff code in the door jam to find out if I had a LSD and if I need to add friction modifiers; I don't. Thanks guys!! I already had some left over 145 as my truck runs it in the rear diff, so I bought another quart in preparation for the change.

SO I am under the car and go and take a look at the drain. Good doG. That is the biggest drain plug I have ever seen. Come back on here and find out it is an 3/4" square drive. I don't have on of those. Go and at least remove the fill plug to check to see if there is anything in the diff. 3/8" drive also weird most cars seem to do 1/2 and 1/2". The filled plug is magnetic and covered in silvery paste. Stick my finger in the hole and pull it out covered in some greenish fluid that looks like someone melted a silver crayon into it. It also seems thinner than 145 weight stuff; could be that it was just warm.

Head over to O reilys and buy a 1/2 to 3/4" adapter: $5.99. Make a feeble attempt to remove it with a breaker bar, then drop the spare (I do love the location of the spare tire crank, and that nice OEM folding lug wrench). Pop on a impact and zip off the drain plug. The fluid that came out was in fact green and silvery. Not as bad as the metal heavy gunk that had built up around the fill hole, but had more metal in it that I would like to see. Wonder if this fluid was every changed (130K). The ring gear teeth felt flat without any noticeable wear.

I did not set up a fluid pump, but use a length of tubing attached to a bottle that I place above the fill hole in the spare tire well. A quick clamp helped me squeeze the sweet vehicular honey out of the bottle, through the tube, into the diff. Yes this assembly popped off a couple of times and covered me with gear oil. Wish it smelled as nice as honey.

I was hoping that this would get rid of the barely on throttle whine I experiencing at speeds above 55 mph. But no, I think that is in the trans.

The EX is all prepped for my mother in law to take for the winter. Going to miss the rig for 5 months or so.

 

[drdoom]

Did you add the 8oz overfill?

 

[MrPulldown]

Did you add the 8oz overfill?

Nope please explain. Just filled till fluid dribbled out of the fill hole.

 

[drdoom]

I changed the oil in my '05, and using the service manual it says to fill to bottom of fill hole, then install fill plug and remove cover from unused sensor port, adding an additional 8 ounces. Not sure if that applies to your model or not.

 

[CDW6212R]

Interesting fill method. I wonder if that applies to the vehicle level also, or jacked up in the rear?

 

[MrPulldown]

I changed the oil in my '05, and using the service manual it says to fill to bottom of fill hole, then install fill plug and remove cover from unused sensor port, adding an additional 8 ounces. Not sure if that applies to your model or not.

Nope. Didn't do that and have never heard of that. I had the back end jacked up a little so I naturally over filled it some. The old fluid was not overfilled either. Sat just below the fill hole. Not too concerned.

 

[swshawaii]

No reason given for the extra PINT (16 ounces) of 75W-140 gear lube.

axle-check-drain-and-fill-general-procedures.pdf

http://www.revbase.com/BBBMotor/TSb/DownloadPdf?id=131011

 

[MrPulldown]

No reason given for the extra PINT (16 ounces) of 75W-140 gear lube.

axle-check-drain-and-fill-general-procedures.pdf

http://www.revbase.com/BBBMotor/TSb/DownloadPdf?id=131011

Thanks for the link. Anyone else want to chime in on this. I once asked about overfilling a Dana 44 axle. The general thought was that this would be bad for the seals. Seems like a weird thing to do. If Ford wanted that much fluid in the diff wouldn't they just make the fill hole higher.

 

[lincolnshibuya]

the fill procedure was revised/updated on August of 2004, so not sure if this applies only to 2004 and up models but I've been filling my diff up to the fill plug only for years without any problem.. I think filling it up a pint more is just prone to leak on the rear axle seals (which is a very common issue)

 

[drdoom]

No reason given for the extra PINT (16 ounces) of 75W-140 gear lube.

axle-check-drain-and-fill-general-procedures.pdf

http://www.revbase.com/BBBMotor/TSb/DownloadPdf?id=131011

Sorry I thought it was 8 ounces, was just going by a not so good memory. Thanks!

 

[drdoom]

Pulldown, so how much fluid were you able to get in there? Just curious, as I don't have the capacities here handy.

 

[MrPulldown]

Less than 2 quarts. Between 1.5 and 2.

No somehing about over pressuring the diff and blowing out seals was the explanation I was give.

 

[lincolnshibuya]

Are you suggesting it's advisable to run the seals dry or oil starved?

if its dry or oil starved it could have been in pieces now or I've already replaced it, 186k+ and I changed the fluid on this truck several times up to the fill hole level only. In fact I've replaced the rear passenger side axle seal twice already due to leaks (I was surprised the right side is still fine... original seal) It's slightly over 1 1/2 bottles of gear oil to fill it up.

 

[CDW6212R]

It sounds like Ford reevaluated the IRS differentials, how much volume they have, how little the fluid can drift to one side and drown a seal etc. Maybe the small IRS size and volume means that a higher level can be used and not get past those seals, which may be a little different than regular solid axle seals. More fluid up to when it could create excess drag, should be good. I didn't know the fill method had changed on any Fords.