Jump to content

300k mile old diff fluid


Recommended Posts

I have a '11 Crown Vic with 300k miles on it and my rear diff fluid looks like this...
 
[PIC]

Been watching some utube vids on how to change this fluid out but after a visit to the local Advance store I've got some questions.  Up til now, forums on the net have led me to believe that all former police cars (which is what mine is) need 75w-140 fluid with friction modifier, but after giving them my VIN at Advance the computer comes back with a fluid suggestion of 80w-90.
 
 
Here's the diff tag...
 
[PIC]

I believe that shows a 3 (L or 1)? 27 which indicates a 3.27 gear ratio, and then an 88 after, which indicates the 8.8 axle.  Not sure what that SYN means, unless it means synchronous?
 
This car is driven VERY sparingly, never hard, and operates in a climate that can get up to 95F in the summer.
 
When the rear is jacked up and one rear wheel is spun, the other moves in the opposite direction.
 
So my first question is... what weight fluid should I use?  Also, I need confirmation if I should use a friction modifier.
 
Next is how to go about changing the oil out.  I'm being lazy here and after watching a vid on how you can extract 80% of the diff fluid out the fill hole by using a flexible hose I'm thinking about just doing it that way.  But if you guys think it's necessary to get all that old fluid out I'll take plate off and do it the regular way.
 
And lastly, if I take the plate off, should I spray all the gears down with brake cleaner to get all the old fluid out, or just let it drain for a while and call it good?

diff 1.png

IMG-0079.JPG

Link to comment
Share on other sites

3L27 means it is a 3.27 locking (traction-lok) rear, 88 definitely means it is a 8.8" size. You need to use the friction modifier. The rest of the numbers are date codes for production. The top row of numbers I am not sure of, but my bet is, one of our resident Ford techs here could decode the rest of it. 

Link to comment
Share on other sites

As stated above, you have a 3.27 ratio trac-lok (i.e. limited slip) differential.  The fact that you can turn it by hand is indicative that the friction plates are worn smooth, basically turning it into a conventional (non limited slip) differential, which is pretty normal and expected for that much mileage. You could replace the friction plates to restore the limited slip function while you have it opened up. Plenty of youtube videos on how to do it.

Either 75-140 or 80-90 oil will work, just make sure it's specified as being for hypoid gears.  80-90 is the normal spec for retail cars, 75-140 is specified for heavy duty applications, including police service.  Basically 75-140 maintains the desired viscosity to a higher temperature, at the expense of possibly hurting fuel economy because it's thicker when cool if you're not driving hard.

 

Link to comment
Share on other sites

Unless you're driving aggressively enough to break the rear tire(s) loose, it doesn't make a difference.  I'm not sure what part of the country you're in, but you'd notice it most in snow. A limited slip differential provides noticeably more traction in snow. It also makes it easier to kick rear end out (fishtail) since both tires will spin instead of just one.

Retail crown vics / mercs / lincolns typically came with the open (non limited slip) differential. Cop cars got the L/S for the added traction.

Link to comment
Share on other sites

On 5/3/2019 at 7:41 AM, akirby said:

Or mud.   After getting my first Ranger stuck in the back yard when one side hit some mud  I learned my lesson and bought a limited slip on the next one and my F150 has the E locker.

Smart choice getting the e locker. Few other options make that much difference for $500 or whatever it costs.  Up here in the rust belt it's impossible to find a 2wd f150 with the e-locker. I've helped two guys look for trucks in the last year that ended up having to special order over just the silly e locker. I guess it's something that most buyers don't understand so dealers don't want the extra sticker for dealer stock inventory.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...