Correct rear Axle Fluid For 04 Grand Marquis

Status
Not open for further replies.
Joined
Jul 23, 2008
Messages
9,808
Location
New Jersey
I never changed the rear axle fluid in this 2004 Mercury Grand Marquis what weight should i use..I am going with Motorcraft from the dealer..Any special additive needed?
 
80W-90 conventional was spec'd originally, but in late '03 Ford revised the spec to 75W-140 synthetic.

If you use Motorcraft, yes you'll need one bottle of XL-3 friction modifier.
 
Originally Posted By: crazyoildude
I never changed the rear axle fluid in this 2004 Mercury Grand Marquis what weight should i use..I am going with Motorcraft from the dealer..Any special additive needed?
Chances are, it's not a posi, very few MGMs had them. They generally have electronic traction control (the '03 in my sig has it, "Precisiontrac"). If so, you won't need any posi additive.
 
bullwinkle has a good point about the posi...likely the car doesn't have it, so no additive needed.

One correction I will make, is to the term "PrecisionTrac"...that has nothing to do with traction control, it refers to the car having a Watts link in the rear suspension instead of a panhard bar. This change was made in 1998.
 
Originally Posted By: RF Overlord
80W-90 conventional was spec'd originally, but in late '03 Ford revised the spec to 75W-140 synthetic.
...

Seems Ford has moved to 75w-140 for most rear ends. I know the trucks have been using it since '97.
For the most part, any syn 75w-140 will work just fine. Advance Auto has Valvoline synpower for $14.99/qt, add another $5 item then use the TRT30 for $15 off.
 
Originally Posted By: drums5757
why dont you just look in your owners manual and see what it recommends
Because, as I stated above, Ford changed the spec after his OM was printed, so he would be taking a step backwards...
 
Originally Posted By: RF Overlord
80W-90 conventional was spec'd originally, but in late '03 Ford revised the spec to 75W-140 synthetic.

+1
thumbsup2.gif

In spite of viscosity shearing, a 75W140 offers higher MOFT and stronger components wear protection than a VII-free 80W90.
Ford revision makes perfect sense in viscosity grade selection.
 
Originally Posted By: RF Overlord
bullwinkle has a good point about the posi...likely the car doesn't have it, so no additive needed.

...


Easy enough to read and decode the axle code on the door sticker....

Probably also has a tag on the rear end...
 
Originally Posted By: crazyoildude
What axle fluid is everyone else using in the Ford rears?

I usually use Valvoline gear oil. They usually have the least expensive 75w140 and it is easy to find.
 
Originally Posted By: crazyoildude
The Motorcraft is $15.00

If your getting it for $15, that is a great deal.
The Valvoline Synpower from advance with coupon is still ~$10 cheaper though.
 
I found it interesting that the go-to shop in my area recommends and uses 80w140 in most of their jobs. When I had them swap gears in my '96 Mustang (8.8 rear) they filled with 80w140, as well. The line they stand by is that the conventional lends to better heat transfer and cooler metal temps of the actual gear faces.
 
Last edited:
80W-90 according to Fords Chemicals and Lubricants

I have been using Chevron Delo ESI 80W-90 and Mobil Delvac 75W-90 in more than a couple of dozen various panthers for the past 10 years.
You could also use straight 90: it's like 75W-140 without shear for the first couple of hundred miles, but it may add quite a bit of heat in some applications.
Always used 75W-140 in the TrackLoc; you may get buy with the thinner grade, but will face a TracLoc diff failure after around 250k miles [from taxi experience]
 
Originally Posted By: buck91
I found it interesting that the go-to shop in my area recommends and uses 80w140 in most of their jobs. When I had them swap gears in my '96 Mustang (8.8 rear) they filled with 80w140, as well. The line they stand by is that the conventional lends to better heat transfer and cooler metal temps of the actual gear faces.

I would concur that an 80W140 offers stronger wear protection in relation to a 75W140 or 90wt due to its higher operating viscoisty rather than base oils per se.
Higher operating viscosity has weaker heat transfer rate(might be indiscernable) and possibly lower 'flash' temperature at gear tooth interface.
Btw, 80W140 that I'm aware of typically claims to be synthetic.
Mind sharing the mineral 80W140 brands used by the mechanics?
 
No idea and cant swear to it either way. Just that thats what they say; they are a regional "authority" on differential work.

I had always heard that 80w140 was NOT synthetic (as opposed to 75w14), though? Never really looked into it at all.
 
Status
Not open for further replies.
Back
Top