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2018 GT PP2 Rear Differential Overheating Issue

Norm Peterson

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Maybe 20F if we add 6 mm spacers to lift rear of hood 6mm and add gurney lip to rear of hood to increase vacuum.
I'm not at all sure this is going to work as hoped, except possibly at very low speeds or when stopped with the engine running. The base of the windshield is a local high pressure region at much speed, and air would tend to go into the engine compartment there rather than out of it. Cool outside air trying to get in is why race cars have drawn intake air at the cowl (not just the drag-race cars and the wanna-be's with their "cowl induction hoods" either).

Air extraction needs to happen much closer to the front of the hood, where you actually have a local low-pressure region.


Norm
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sigintel

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I'm not at all sure this is going to work as hoped, except possibly at very low speeds or when stopped with the engine running. The base of the windshield is a local high pressure region at much speed, and air would tend to go into the engine compartment there rather than out of it. Cool outside air trying to get in is why race cars have drawn intake air at the cowl (not just the drag-race cars and the wanna-be's with their "cowl induction hoods" either).

Air extraction needs to happen much closer to the front of the hood, where you actually have a local low-pressure region.
Norm
Yes! Excellent point. I was running no lower grill and excess under hood pressure. Plus my entire front clip was completely remounted for aero: bumper/rad support, fender supports, hood, fender skirts and under tray all modded.

I also tested with yarn pieces taped on hood gap to see them get spit out or sucked in depending on speed. Would have to search forum to find that post. I will do this again on the 2018.

Keep in mind, I modified the 2015 entire front body extensively to lower my bumper and hood top leading edge more than 20 mm. Both the height and rotation were changed. The fender/bumper interface was also pushed outward by 3/4” to allow running 305 on OEM FRPP Track or even stock struts. This was in 2016, and Ford came to the same conclusion on 2018 in development about the same time (...funny thing about that). All this is in posts on the forum.

Yes, it would be preferable that he cut a hole about 5.2 inches back from front hood edge about 10” long and 27” wide. Or run a 2020 GT500 hood. Buuuuut, cutting the hood up is pretty expensive if you plan on return to stock one day. Gurney flap on rear of hood is way cheaper and easy to remove.
 

Performance nut

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Yeah, why is this not a thing yet?

FP?
Steeda?
Anyone?
I spoke with a guy who makes pre-S550 finned differential covers. Seems that the consensus is that a finned differential covers will not help our cars at all due to spacing and airflow. He recommended a cooler for our cars.
 

Bahndvr

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Performance nut

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2018 Ford Mustang GT Performance Package Level 2 at Lightning Lap 2018
There is one thing this Mustang needs besides a proper name.
September 2018 By Multiple Authors Multiple Photographers 18 Comments


View 31 Photos
lightning-lap-2018-2018-ford-mustang-gt-performance-pack-level-2-ll-lead-1536943674.jpg


Lap Time: 2:53.8
Class: LL2 | Base Price: $44,685 | As-Tested Price: $51,770
Power and Weight: 460 hp • 3843 lb • 8.4 lb/hp
Tires: Michelin Pilot Sport Cup 2, 305/30ZR-19 (98Y)

return01-2018a-1537330298.jpg


Shelby. Mach 1. Cobra. Boss. In the 54-year history of the Mustang, there’s been no shortage of speed-soaked, track-worthy badges. Yet Ford’s newest road-course beast is a horse with no name.

The Performance Package Level 2 kit builds from the ground up, starting with a set of Michelin’s track-magic Pilot Sport Cup 2 tires—same size at each corner—that stick to the pavement like duct tape. The Mustang hammers through Turn 1 at 1.13 g’s, cornering harder than the McLaren 720S, Porsche 911 GT3, and Ford’s own supercar. It turns in instantly, steers with perfect clarity, and changes direction with the kind of neutral balance you wouldn’t expect from a front-engined car. Magnetorheological dampers rein in body motions. Six-piston Brembos gnaw on upsized front rotors for indefatigable braking. In taming VIR, the Mustang GT PPL2 trades American brashness for the world-class manners of a Porsche GT car.

The revised 460-hp V-8 found in all 2018 Mustang GTs now redlines at 7500 rpm and, with the $895 active exhaust, finally sounds properly pissed. Funneled through the Level 2’s shorter-ratio Torsen limited-slip diff, the furious 5.0-liter leads this Mustang to a lap that’s just two seconds off the pace of the Shelby GT350R in 2016, which packed another 66 horsepower and a base price of $63,495.

In addition to the aforementioned, the PPL2’s $6500 upcharge over a base GT buys a front splitter, a unique spoiler, a larger radiator, a trio of chassis-stiffening braces, and retuned suspension, steering, and anti-lock-braking logic to play nice with the Cup 2 tires. But with no differential cooler, the rear axle overheated every time we took the Mustang out, often in as few as three hot laps, and even with easy laps staggered between them. So there is one thing it needs besides a proper name.
 

NightmareMoon

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I wonder if they actually gave the car much time to cool down between drivers or just tag teamed it all day with no chance for the diff temp to come back down. im guessing they flogged it pretty bad.
 

PRE-Z06

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I wonder if they actually gave the car much time to cool down between drivers or just tag teamed it all day with no chance for the diff temp to come back down. im guessing they flogged it pretty bad.
I'm sure they enjoyed driving it as much as the other cars, but they don't mention any of the others having diff temp issues. It probably is the car with the fastest lap time they've run w/o a diff cooler, not sure that's an award I'd be proud of though.
 
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93tankus

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Hey Everyone,

Thought I would share...

I had a wonderful track day today in my PP2. Since my last track outing, I changed the rear end oil to BG 75w-140.

I ran four hard sessions today (each around 15 -20 mins) and had zero overheating diff issues. I think the highest temp I saw was around 210 degrees.

Granted, the ambient temp was lower today (70 degrees) versus last time (90 degrees). I’m sure that helped out considerably. Diff cooler in the future, but for now, it’s all good!

Anyway, it was all I could ask for! That car is a blast!
 

Mountain376

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Hey Everyone,

Thought I would share...

I had a wonderful track day today in my PP2. Since my last track outing, I changed the rear end oil to BG 75w-140.

I ran four hard sessions today (each around 15 -20 mins) and had zero overheating diff issues. I think the highest temp I saw was around 210 degrees.

Granted, the ambient temp was lower today (70 degrees) versus last time (90 degrees). I’m sure that helped out considerably. Diff cooler in the future, but for now, it’s all good!

Anyway, it was all I could ask for! That car is a blast!
What tracks have you been at?
 

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FastCarFanBoy

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be interesting to see how long it lasts in 90deg heat with the 75w-140.
 

JohnD

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be interesting to see how long it lasts in 90deg heat with the 75w-140.
Um-m--m, not very long.

I run the BG 75W-140 and at Mosport, er, CTMP on a hot day, 31C, I was getting a diff overheat error in 5- 6 laps, that was with 1/2 hour cool down between sessions. I even skipped a session and it still overheated in 6 laps. That's a track where you're on it hard all the time, and it's never happened anywhere else. I'm going to put the FTBR diff cooler kit on it, the thing's marginal no matter what weight of lube you've got in it.
 

Mountain376

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Just over to Gingerman Raceway, near South Haven, MI.
Nice. I’m hoping to get out to Gingerman before the end of the season...

Maybe the issue really just shows on higher speed tracks (high diff RPM)?

Were you driving much different than the last outing?

The fluid viscosity change and exhaust wrapping might be enough to just get the car by for the most part. Until you start pushing the car 8-10/10ths.

Are all you guys getting just the first warning or the second?
 
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93tankus

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Nice. I’m hoping to get out to Gingerman before the end of the season...

Maybe the issue really just shows on higher speed tracks (high diff RPM)?

Were you driving much different than the last outing?

The fluid viscosity change and exhaust wrapping might be enough to just get the car by for the most part. Until you start pushing the car 8-10/10ths.

Are all you guys getting just the first warning or the second?
I wasn’t driving much differently from the first time. If anything, I was probably a bit more tentative the previous time.

The only other thing that was different this time around was that I had it in “Track” mode (vs “Sport” mode the previous time). Not sure if that would have any bearing on diff temps.

I have to think the cooler ambient temps helped considerably. The 75w-140 oil may have made a small difference? But probably nothing notable, if at all.
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