Diff Fluid swap

[Angrey]

Searched, couldn't find some specifics, if there's another post, please direct me.

Found the procedure 205-02.

However, it simply states that for vehicles with a cooler, to run the pump for two minutes using a "scan" tool. Does anyone have a trick for priming filling the cooler system without tricking the computer?

I guess I could drive the car for a bit and then top off, but the top off instructions are a bit vague/problematic. How in the **** am I supposed to measure 9mm from the hole opening for top off? Is it really the end of the world to fill it until fluid starts to come out? Is that extra .3" of fluid fill going to adversely affect the cooling characteristics/ring spin of the fuid?

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[Angrey]

And for anyone going with Redline or an alternate gear lube, are you also adding the friction modifier? I thought that was only required for limited slip diffs with clutch packs.

 

[Jaymar]

We were always told the manufacturer "short" fill recommendations were to prevent heat expansion from puking out the vents. That being said, I had spent decades filling to the hole without detriment and I've never had that scenario happen to me.

 

[Tomster]

Forscan will run the diff cooler. I've done it many times. The best and easiest way to change your diff fluid is to measure exactly what comes out and replace it with the same amount. Sooner or later the cooler will run and that will take care of that.

I do belive there is a warning not to run the diff cooler pump with cold fluid. It is viscous and can damage the pump, so they say.

 

[mikedahammer]

Every time I changed mine I followed the Driver Mod youtube video. It never failed me and I used the same fluids he recommended.

 

[Tomster]

Just be aware that the fill hole is not to be topped up. I believe spec is 10mm below the hole. I once filled to top (like you do the trans fluid) and fluid wound up getting slung out of the vent and all over my brake rotor during track use.

 

[Cobra Jet]

Just be aware that the fill hole is not to be topped up. I believe spec is 10mm below the hole. I once filled to top (like you do the trans fluid) and fluid wound up getting slung out of the vent and all over my brake rotor during track use.

Good info - and about the rear diff vent, folks should check to make sure that vent isn’t plugged too….

 

[Angrey]

Forscan will run the diff cooler. I've done it many times. The best and easiest way to change your diff fluid is to measure exactly what comes out and replace it with the same amount. Sooner or later the cooler will run and that will take care of that.

I do belive there is a warning not to run the diff cooler pump with cold fluid. It is viscous and can damage the pump, so they say.

I can't exactly do that because the vent tube popped off and I've leaked at least some fluid.

And I don't have FORSCAN ability any more, I'm on a MOTEC M150 now.

And shame on Ford. What a bunch of dumbasses. It doesn't take a PE stamp to say "Hey Bob, call the guys who make the rear diff covers and tell them to lower the fill bung by .3" that way whenever our techs or our customers need to fill the diff, all they have to do is fill it to the bottom of the fill opening. We'll probably save a zillion man hours across everyone who has to somehow try to fill to a .3" level below the fill bung and either add more or drain some and measure again."

I'm probably going to drain it, fill it till it overflows, drive it, check it and then adjust.

 

[Jaymar]

I can't exactly do that because the vent tube popped off and I've leaked at least some fluid.

And I don't have FORSCAN ability any more, I'm on a MOTEC M150 now.

And shame on Ford. What a bunch of dumbasses. It doesn't take a PE stamp to say "Hey Bob, call the guys who make the rear diff covers and tell them to lower the fill bung by .3" that way whenever our techs or our customers need to fill the diff, all they have to do is fill it to the bottom of the fill opening. We'll probably save a zillion man hours across everyone who has to somehow try to fill to a .3" level below the fill bung and either add more or drain some and measure again."

I'm probably going to drain it, fill it till it overflows, drive it, check it and then adjust.

I'm not going to disagree with those that have experienced otherwise, but guess how many technicians around the world have done exactly that?

 

[Tomster]

I'm not going to disagree with those that have experienced otherwise, but guess how many technicians around the world have done exactly that?

That is what they do. And if you don't track the car and do high G turns, you won't vent fluid.

You can take a paperclip and use it as a guage if you want to do it to spec.

 

[ice445]

I came up with a simple solution for the 9mm below the fill plug nonsense. Just take a standard zip tie, measure 9mm up from the tip, then make a mark. Fold the zip tie 90 degrees at the mark you made. Then slide it over the edge of the fill hole so it's pointing straight down. Add fluid until your zip tie dips into the oil at the very tip. You don't have to get it perfect, anywhere from the very tip to halfway to your mark is probably gonna be just fine.

Obviously make sure the car is level as well.

 

[Optimum Performance]

Searched, couldn't find some specifics, if there's another post, please direct me.

Found the procedure 205-02.

However, it simply states that for vehicles with a cooler, to run the pump for two minutes using a "scan" tool. Does anyone have a trick for priming filling the cooler system without tricking the computer?

I guess I could drive the car for a bit and then top off, but the top off instructions are a bit vague/problematic. How in the **** am I supposed to measure 9mm from the hole opening for top off? Is it really the end of the world to fill it until fluid starts to come out? Is that extra .3" of fluid fill going to adversely affect the cooling characteristics/ring spin of the fuid?

Yes, not advised to fill it till it pours out, these things run pretty hot even with a cooler.

Our kit always included the dipstick.

As far as changing it without a service tool, either put in what you took out (which requires a lot of faith it was properly filled to begin with) measure the level before draining to verify.

Or you can fill it, drive it and recheck it. Having the tool allows you to also flush the system. By now I think most scan tool apps have the ability to cycle the pump.

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