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



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...



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, long distances at 60-65mph but 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?

 

SYN for synthetic gear oil? 3:27 gear ratio. Limited slip. 8.8" ring gear. Built 10 October 2008 at the Van Dyke plant. Get all the sludge out instead of pouring clean oil on top of it. Even I know that.

https://www.differentials.com/techni...20Tag%20Number

 

Thanks Frank, appreciate the advice. Couple wrap up questions...

What advantage is there to using the more expensive Mobil 1 synthetic as opposed to a cheaper Valvoline full syn... $20 a bottle vs. $13, times 3.

Also, I've been given advice to replace the clutches and 'steels?' in the diff as mine are probably worn out. What advantage in performance would I gain by doing this and is it expensive/ worth it?

 

I have no idea whatsoever.

 

This venue is for atv/utv offroad vehicles. You would get far better answers on an automobile forum.

 

It's ATV Connection. Get out of here with your little red buggy and ride like a man.

 

Rear diff fluid is one of those things that gets neglected in your truck or in this case, rear wheel drive car. I doubt the fluid has ever been changed in my current 03 Silverado. Its only 2wd so no front diff to change out. It has about half that many miles(154K currently) but I'm sure it doesn't look great either. 300K miles on a 2011 Crown Vic, that's an insane amount of miles. Was it a taxi or police car at one point? Otherwise I can't imagine putting 40K miles a year on a vehicle.

 

Cop car.

I don't change my oil myself anymore and most oil change places will check the diffs and transmission and anything else they can charge you to change the fluid in. One place I went to had a laminated card with circles on it and they put a little bit of each fluid on its own spot to show you.