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2018 GT PP2 Rear Differential Overheating Issue

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93tankus

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PoppinJ, I'll be interested to see what your results are. I just swapped out oil to 75W-140, and was going to wrap exhaust as well before my next track day.

Best of luck!!
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XPystchrisX

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Ok, 75w140 and wraps installed, albeit sloppily. I shall see how it holds up next weekend in 100 degree temps. Also, does anyone know what this is? The thing im pointing to in the pic right behind the diff. Its like a flexible rubber... somthing. I thought the bolt was backing out at first.
That's not on my 2015. I'm getting ready to do diff bushings soon, and that's one of the places Steeda has you install their inserts. I'm wondering if the 2018's have that in response to some of the diff noise complaints?
 

PoppinJ

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That's not on my 2015. I'm getting ready to do diff bushings soon, and that's one of the places Steeda has you install their inserts. I'm wondering if the 2018's have that in response to some of the diff noise complaints?
I'm not sure. I tried to Google the part number to see but nothing came up. Does anyone know how to look it up with Ford's invantory or something?
 

PoppinJ

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Ok reporting back post track day. I made three changes which is less than ideal to isolate what helps the most but hey, whatchagonnado?

Track Day temp low, 80, high 100.
First Session at 9:30am, last session at 2:50pm. 4 25 min sessions.
I made three changes since my last track day when I got the diff warning reliably within 15 min each session, same(ish) outdoor temps. First, the exhaust wrap, second 75w140 Redline synthetic diff fluid, third turned off traction control so the differential wasn't having to fight my rear brakes. I'd be willing to bet that no TT is hugely impactful as it has been chewing up my rear pads, so I know it was creating a lot of friction.

First two 25 min sessions were completely trouble free. Outdoor temps prob not higher than low 90s. The diff got up to around 260 max from what I could tell. Session three with temps mid to high 90s I got the warning right as before my cooldown lap at 20(ish) min. I prob could have gotten 1 more lap in had it not come on. The ultimate goal would be to get 25 trouble free min out of the car before it gets to hot.

I noted the temp at the start of session 3 at 160, so it already started pretty warm. This was after prob 2 hours of sitting due to lunch. The diff would really really be benefited by some sort of passive cooling. Ive tried to take a lap slow to allow it to cool but it really doesn't help. Once the temp gets high, it stays high. It takes a long time for the temps to come back down.

Session 4 outdoor temps around 100/101. Diff temps were already slightly elevated at the start. I got about 18(ish) min in before it triggered the warning. Tried to take a slow lap, didnt help. Finished with axle temps at 280 and came off slightly early.

So all in all Im very pleased. I pushed the car MUCH harder than before and was able to get almost all my session time in. I would assume if temps were in the 80s that it would never get hot enough to trigger the warning, we shall see in the fall. Again, once that thing gets hot, it stays hot with nothing to cool it down but time. I defiantly got more time out of it than last time though so overall Im pleased.
 
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Norm Peterson

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What about getting a portable, plug-in-the-power-outlet 12-volt fan and aim it at the diff to improve cooling between sessions? You might have to start the car and let it idle every so often, but you'd be in neutral so the diff itself would not be generating any heat.

For a bit more $ and probably quicker results, maybe a cordless leaf-blower could be re-purposed . . .


Norm
 

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PoppinJ

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What about getting a portable, plug-in-the-power-outlet 12-volt fan and aim it at the diff to improve cooling between sessions? You might have to start the car and let it idle every so often, but you'd be in neutral so the diff itself would not be generating any heat.

For a bit more $ and probably quicker results, maybe a cordless leaf-blower could be re-purposed . . .


Norm
Thats an interesting idea. It would likely help a bit, but again, there are no passive cooling fins or anything on it so it can only dissipate heat through the housing. The same problems would exist with it being tucked under the exhaust with terrible airflow but I bet it would help, especially something more powerful like a leaf blower. It would be a hassle though. Honestly, If it only triggers the warning at the end of the day on 100+ degree days then I'm pretty happy. If it doesn't trigger on sub 90 degree days on 25 min sessions thats gonna be good enough for me 90%+ of the time.
 

Mountain376

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What is the rear axle housing vent like on these cars? How restrictive are they? This is something only worth marginal improvements, but worth considering.

Outside of a cooler, and with what you've done already (fluid, exhaust wrap/shielding), running some sort of scoop or playing with under-body aero (play with low and high pressure areas) is going to help. A scoop of some sort would be difficult to place. The GT350 under-bosy parts at the rear of the vehicle help direct some under-car air up, past the differential cooler area and out the rear fascia... maybe something creative can be done there to make air flow past the differential itself.
 

NightmareMoon

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What about getting a portable, plug-in-the-power-outlet 12-volt fan and aim it at the diff to improve cooling between sessions? You might have to start the car and let it idle every so often, but you'd be in neutral so the diff itself would not be generating any heat.

For a bit more $ and probably quicker results, maybe a cordless leaf-blower could be re-purposed . . .

Norm
If it doesn't cook on your first sessions, and you just need to cool the diff between sessions, that can be done. With enough crew people, water, and airflow its a solvable problem. You'll need a large fishtank, some fishes, 3 rednecks, and ...
 

NightmareMoon

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I think if someone would just make a suitable finned diff cover, it would sell pretty well.

Ford Performance, I'm looking at you.
 

Mountain376

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I think if someone would just make a suitable finned diff cover, it would sell pretty well.

Ford Performance, I'm looking at you.
Yeah, why is this not a thing yet?

FP?
Steeda?
Anyone?
 

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Mountain376

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Thats an interesting idea. It would likely help a bit, but again, there are no passive cooling fins or anything on it so it can only dissipate heat through the housing. The same problems would exist with it being tucked under the exhaust with terrible airflow but I bet it would help, especially something more powerful like a leaf blower. It would be a hassle though. Honestly, If it only triggers the warning at the end of the day on 100+ degree days then I'm pretty happy. If it doesn't trigger on sub 90 degree days on 25 min sessions thats gonna be good enough for me 90%+ of the time.
I was thinking about this today... One thing I noticed going through the data from one of the track days I did in my 1LE is the effects of heat soak on the fluids. Even with a cool down lap at the end of a session, and the car sitting between sessions, my fluid temps would be hottest the first and maybe second lap; through the following laps airflow and the coolers brought everything down. So, maybe it is worth trying to eliminate heat soak as much as possible if you’re not going to run a cooler...You can buy $30 camping fans that use like 6-8 D batteries and flow pretty good (I have one). Might get you a lap or two.

As far as another cooler option, what about retrofitting the 2013-14 GT500 TP differential cooler? Just use the pump and the heat exchanger (or a similar small aftermarket one), then plum in your own lines?

Edit: Nm, that pump, DR3Z-4C158-A, is $800+ alone. It’s 1.5 gpm as a data point.

You can put together something that will be good enough for track days, only, for around $500, but you’re going to have to put in the time and energy to piece it all together.

TrackMustangsOnline.com is a good source, even if it’s S197 stuff.
 
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sigintel

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Thats an interesting idea. It would likely help a bit, but again, there are no passive cooling fins or anything on it so it can only dissipate heat through the housing. The same problems would exist with it being tucked under the exhaust with terrible airflow but I bet it would help, especially something more powerful like a leaf blower. It would be a hassle though. Honestly, If it only triggers the warning at the end of the day on 100+ degree days then I'm pretty happy. If it doesn't trigger on sub 90 degree days on 25 min sessions thats gonna be good enough for me 90%+ of the time.
Awesome info! Thanks!

Any opportunity to drive around between sessions at 40-60 mile an hour for about 10 minutes?
Did you keep hood open between sessions?
I am still tempted to just add a brake duct type fan and just cut a hole.

Maybe add an aluminum whirligig on the pinion flange?
If its spinning in the air and directly mounted to the pinion, it should act as a heat sink.
We really need air temperature readings around the diff, if its all 200+ degree air, any passive cooling will be limited.

Also thinking to take some cheap lowes hardware aluminum and cut some tabs/brackets long enough to wrap around trans cooler lines.
Then get trans line bender out and make a prototype trans line in shape of rear diff.
Then wrap tabs around diff shaped lines, add a 90 bend in each and drill hole for diff bolt.
Basically pull one bolt at a time and put back thru sandwiching aluminum tab that is wrapped on shaped trans cooler line.
This would run off trans cooler circuit so the trans cooler would need to be relocated to virgin air passenger fender (I will do this anyway on the 2018).
The idea would be add capacity to transcooler loop and add a diff loop in series.
Would need a temp sensor to make sure not overheating fluid regardless of order of the loops.
If this works, would make a jig to pump out as many diff "loops" as needed at cost.
Nice brackets to clamp the diff line could be made with a press and a piece of correctly sized rod and block of wood.

For the manual guys, if they aren't going to add a trans cooler, then they could also use this but will run a secondary coolant loop:
This will require an electric water pump like a Stewart. The new radiator (rad2) will be a small one located in the drivers fender well with the pump on the cold side.
You will disconnect the existing restriction/diverter in the lower main radiator hose that on stock is used to divert a weak flow thru the oil cooler (this will increase your main radiator capacity as well).
The water will go thru rad2 and exit cold into the pump that will then drive into the reused restriction/diverter and then into the existing coolant to oil cooler for the engine oil and back to rad2.
The diverter ports will be used to feed the diff cooler loop. There may be a more elegant way with some off the shelf fittings to accomplish this.

This is all raw ideas and concepts. Surely someone will say I am an idiot for trying to drive this forward, lol.
If you see a flaw, please pitch in! Add in some more brainstorm too!
 

Kep4

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I think if someone would just make a suitable finned diff cover, it would sell pretty well.

Ford Performance, I'm looking at you.
The aftermarket for Mustangs is 'Yuge' so I sincerely hope someone out there is working on one. Seems like there's room for a finned cover with reasonably deep fins, though I haven't taken the time to crawl under mine yet to see first hand.
 

Mountain376

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What Camaro does is essentially what you are talking about. The differential on the G5 ZL1 and the G6 SS/ZL1 cars are not cooled with their own, separate cooling circuit. What GM does is use the transmission cooler system by having the lines loop into the differential unit. Now, GM does use a small heat exchanger inside the differential unit, but the idea is the same. The overall system is cooled by one, fairly large, heat exchanger at the front of the car. Automatic cars also utilize the cooler inside the radiator as well.

The more I look at the underside of the Mustang, where everything is located (exhaust, suspension links, the IRS cradle structure, the diff housing, axles, etc.), I beginning to think that a finned cover may not do much. The reason is airflow - you won't get much since the S550 diff is pretty well tuck up and into the rear structure; you can argue, then, why did Ford and the aftermarket do a finned cover for the SRA cars, but the SRA sits lower and the architecture of everything in the rear of the older cars has less in the way.

If you look back, the early designs of the S550 did, indeed, have a finned cover:
http://www.drivingenthusiast.net/se...is-2015-mustang-irs-pre-production-prototype/

I think something creative, at least to get through a 20-minute session, could be done with brake ducting being placed strategically under the car to direct airflow towards the diff. You will see something similar done on amature/semi-pro race cars for the rear brakes and, in a similar functionality, with all levels of racers as an ad-hoc AC system through the front windows (works really well, I can vouch for it).

Also, consider a breather element in place of the jiggle cap if you only drive the car three-seasons. There is heat in the internal air, too.

Worthwhile read if this isn't posted/seen already:
https://torsen.com/667-2/
2015-Mustang-spy-photo-10-1024x625 (1).jpg
2015Mustang_spyphoto_IRS-12.jpg
ducts.JPG
ducts2.JPG
3-2015-Mustang-IRS-Upgrades.jpg
 

NightmareMoon

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Good points about the placement of the diff and airflow re: finned covers.

I think some brake ducting wouldn't be that hard to work out. Maybe some brake ducting with a water injection system? (half j/k)
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