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Changing Diff fluid in a 2017 GT 350

cghawk

TMO Intermediate
17
13
Arvada CO
So I bought the full shop manual and everything looks super simple to change diff fluid but the manual says to run the diff cooler pump with a scan tool for 2 minutes so you can properly check the fluid level ( I would imagine you might want to also to fully empty the system ?)

How are you guys doing it ? With a scan tool or other means ? If scan tool which one are ya using ? I don't need the full boat scan tool capabilities just want to simply switch the diff pump on/ off so looking for inexpensive ( read cheap!)

Thanks for any input !

Cheers !
 

RaiderJatt02

TMO Advanced
109
131
I would like to know this too. I changed my diff and transmission fluids a few weeks ago but didn't have a scan tool so I skipped that step. I figured, I changed MOST of the fluid so I should be good for a while. I was hoping ForScan could do it but I couldn't figure out how.
 

JAJ

TMO Addict
785
725
In the V6L
Hook up Forscan, connect to the PCM and look for a PID called "R_DIFF_PUMP". If you find it, see if you can take control of it and change it from OFF to ON. If you can, then you can turn the pump on and off from Forscan. I have Ford IDS/VCM II so it never occurred to me to try Forscan. Good luck.
 

JAJ

TMO Addict
785
725
In the V6L
I just had mine changed at the dealer and of course they used IDS to properly cycle it. Are you guys removing the diff cover?
I'm planning to change mine in the next couple of weeks. The Motorcraft Service instructions say just disconnect the lower cooler line from the diff and allow the diff to drain, then unscrew the cooler fitting from the lower cover and "inspect". Then put it back together and fill it back up. Cover stays on.
 

cghawk

TMO Intermediate
17
13
Arvada CO
IMG_9425.JPG
Manual doesn't say to pull it so I was just going do it per the manual, it was just the cycling of the pump I didn't do !

I think in most cases I do a better job on servicing my cars than most dealers and I guess I'm kinda spoiled as I have a 2-post lift so it makes under the car things a breeze !
 

mattlqx

Mustangless
453
205
Chandler, AZ
When I changed mine, I didn't run the pump because I didn't really have the means. It still took basically the expected amount of fluid so I wasn't too worried about it. I do think this gives me some motivation to mess around with Forscan again though.
 

8250RPM

TMO Addict
I have a snap on verus to do mine, But I mainly use it for work.
You could buy a spare diff temp sensor and put it in a cup of hot water while it's plugged into the cars harness while the cars running to activate the pump. Or you could also use a jumper wire and a momentary switch to activate the diff pump.


Sent from my iPhone using Tapatalk
 

mattlqx

Mustangless
453
205
Chandler, AZ
I had a chance to give Forscan a shot and indeed it can write to the pid for the diff pump! When toggling, it didn't switch it on constant (with the car running or not) but it did switch it on very noisily for about 5-7 seconds. That's probably enough to purge the cooler so this is the maintenance function we were looking for. Awesome!

Screen Shot 2017-04-10 at 4.39.08 PM.png
 

cghawk

TMO Intermediate
17
13
Arvada CO
Awesome ! Great news ! That was what I was looking for ! Thank you for trying that !

Guess I gotta get Forscan !
 

JAJ

TMO Addict
785
725
In the V6L
So this thread has been quiet for quite a while, so since I changed my diff fluid again yesterday, I thought I'd update a couple of points.

To drain and refill my TP car with the cooler, it took exactly 1 quart plus 20 ounces from a second bottle of MC 75w85. With 4 ounces of XL3 added in, the total fill is 56 ounces. I made myself a little dipstick out of a chunk of wire to confirm the fluid was exactly 9mm below the fill hole. I didn't remove the lower cooler fitting - I unplugged the cooler line, let it all drain, then plugged it back together and got on with filling it.

As part of the process, you have to run the cooler pump for two minutes. I ran it first with my IDM/VCM2 setup. As others noted above, it buzzes for about 5-7 seconds and it gets quiet. But it's still running - it hums quietly moving the fluid through the cooler. Then I tried using Forscan with OBDLink MX, just to see whether it was a cheaper way to get the same result. Well, it will run the pump, but it seems to keep cycling the startup buzz over and over again, rather starting it and running it quietly the way IDS does. I'm not sure I like that, but hey, that's the story for those that might be wondering.
 

Black Boss

TMO Addict
1,898
1,788
Michigan
For track use with more frequent changes, you are better off not emptying the cooling system or running the pump. Just refill using the non-cooler quantities as the cooling circuit stays full. Running the pump with cold fluid will lead to pump wear and eventually failure.
 

j3st3r

Brian S.
577
301
Tennessee
For track use with more frequent changes, you are better off not emptying the cooling system or running the pump. Just refill using the non-cooler quantities as the cooling circuit stays full. Running the pump with cold fluid will lead to pump wear and eventually failure.
Very similar to what I did, I simply drained the fluid into an old oil jug to keep track of how much came out, and that is how much I put back in.
 

JAJ

TMO Addict
785
725
In the V6L
For track use with more frequent changes, you are better off not emptying the cooling system or running the pump. Just refill using the non-cooler quantities as the cooling circuit stays full. Running the pump with cold fluid will lead to pump wear and eventually failure.
And that's exactly why I posted the amount needed to fill the system when you drain the diff and the lower hose by pulling the lower hose. When you drain it, you lose some of the pump prime, but if you put 56 ounces including the XL3 back into the system, the first time it runs under track conditions, the fluid will be at the correct level.
 

Black Boss

TMO Addict
1,898
1,788
Michigan
And that's exactly why I posted the amount needed to fill the system when you drain the diff and the lower hose by pulling the lower hose. When you drain it, you lose some of the pump prime, but if you put 56 ounces including the XL3 back into the system, the first time it runs under track conditions, the fluid will be at the correct level.
Agreed, my recommendation was to avoid running the pump with cold fluid repeatably.

I err on the side of caution and change Diff/Tranny fluid every 12-15 hours of track time.
 

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