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2018 GT PP2 Rear Differential Overheating Issue

Rodan

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Actually, some kind of a water/alcohol misting system could theoretically work. Spray directly on the diff, and it would evap fast enough that it would never hit the track. It's obviously not the kind of thing a manufacturer would put on a production car, but it could work for a low buck solution on an occasional HPDE car. You could even make the whole thing easily removeable...
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sigintel

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Actually, some kind of a water/alcohol misting system could theoretically work. Spray directly on the diff, and it would evap fast enough that it would never hit the track. It's obviously not the kind of thing a manufacturer would put on a production car, but it could work for a low buck solution on an occasional HPDE car. You could even make the whole thing easily removeable...
Nice! Now thats brainstorming.
A cheap hose run off t valve on windshield washer line. Run thru cabin along floor and spray on top of diff.
That would be soooo easy
 

JohnD

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Realistically, the only solution to this is to put an oil cooler in. FTBR makes a nice looking kit, if I run into heat issues with it that's what I'll be doing. So far, with 20 minute sessions, I haven't had a problem.
 

sigintel

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Realistically, the only solution to this is to put an oil cooler in. FTBR makes a nice looking kit, if I run into heat issues with it that's what I'll be doing. So far, with 20 minute sessions, I haven't had a problem.
Disagree.
Realistically, FTBR is asking $800.
Asking owners to spend $800 to just go run a couple track days?
Yea, you could do that.

My goal is to come up with a solution that lowers the barrier to entry for myself and anyone else that wants to go run track days without diff issues.

On the Whippled 2015, I just paid $800 for 3 recycled 3.15 diffs to cover 2 years of track time. The cheaper 3.15 non Torsen is more or less a wear item at higher torque levels.
 

sigintel

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Update:
Ran Saturday at DWA on the short course for max torture.

Diff was 205 at 10AM 87F just hauling ass around back roads.
225 CHT and 205 on the diff.
After 16 minutes of flogging on the short course:
CHT was 230-235 with short shifting below 7000
CHT was 235-242 going to 7400 on back straight and climbing fast with diff at 210.
The sketchy part is how rapidly the temps rise at high rpm like the pump is vapor locking.
I suspect the pump has got some surfaces on inlet seeing a couple pounds of vacuum causing cavitation at high rpm.
Brought it in for hood open cool down.
15 minutes later it took 5 laps and that that was with head temps hitting 243 again quickly and diff following at 207 (Ambient temps hit 96F),
Took a cool down and bailed as the engine temps were way too high.
No point in continuing on the factory 5w20 and factory Tstat.

Will try again after changing the oil and tstat (Reische 170 or similar).

Diff temperature was 202F just from running around on the highway. It really seems that the diff is just bathed in the heat coming off the trans and exhaust. I am going to look at adding air scoops maybe either side of bell housing and ducting from there back to in front of diff. Dont really need to even hit the track with it until I can maintain 160F at 90F ambient while just driving around on highway.
 

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FastCarFanBoy

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Update:
Ran Saturday at DWA on the short course for max torture.

Diff was 205 at 10AM 87F just hauling ass around back roads.
225 CHT and 205 on the diff.
After 16 minutes of flogging on the short course:
CHT was 230-235 with short shifting below 7000
CHT was 235-242 going to 7400 on back straight and climbing fast with diff at 210.
The sketchy part is how rapidly the temps rise at high rpm like the pump is vapor locking.
I suspect the pump has got some surfaces on inlet seeing a couple pounds of vacuum causing cavitation at high rpm.
Brought it in for hood open cool down.
15 minutes later it took 5 laps and that that was with head temps hitting 243 again quickly and diff following at 207 (Ambient temps hit 96F),
Took a cool down and bailed as the engine temps were way too high.
No point in continuing on the factory 5w20 and factory Tstat.

Will try again after changing the oil and tstat (Reische 170 or similar).

Diff temperature was 202F just from running around on the highway. It really seems that the diff is just bathed in the heat coming off the trans and exhaust. I am going to look at adding air scoops maybe either side of bell housing and ducting from there back to in front of diff. Dont really need to even hit the track with it until I can maintain 160F at 90F ambient while just driving around on highway.
low 200 diff temps are nothing to be concerned with, those CH temps are high though.
 

Mountain376

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Update:
Ran Saturday at DWA on the short course for max torture.

Diff was 205 at 10AM 87F just hauling ass around back roads.
225 CHT and 205 on the diff.
After 16 minutes of flogging on the short course:
CHT was 230-235 with short shifting below 7000
CHT was 235-242 going to 7400 on back straight and climbing fast with diff at 210.
The sketchy part is how rapidly the temps rise at high rpm like the pump is vapor locking.
I suspect the pump has got some surfaces on inlet seeing a couple pounds of vacuum causing cavitation at high rpm.
Brought it in for hood open cool down.
15 minutes later it took 5 laps and that that was with head temps hitting 243 again quickly and diff following at 207 (Ambient temps hit 96F),
Took a cool down and bailed as the engine temps were way too high.
No point in continuing on the factory 5w20 and factory Tstat.

Will try again after changing the oil and tstat (Reische 170 or similar).

Diff temperature was 202F just from running around on the highway. It really seems that the diff is just bathed in the heat coming off the trans and exhaust. I am going to look at adding air scoops maybe either side of bell housing and ducting from there back to in front of diff. Dont really need to even hit the track with it until I can maintain 160F at 90F ambient while just driving around on highway.
Man, you’re running your car with 5w-20 on track... You need to up your viscosity to something in the 40’s or 50’s.

Also, the temp rise in engine temps is what your going to see between 7k and 7.4/7.5k. RPM will do that, especially as you go above 7k. The GT350 doesn’t just have coolers because it’s track intended - it’s also because the RPM.
 

sigintel

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Man, you’re running your car with 5w-20 on track... You need to up your viscosity to something in the 40’s or 50’s.

Also, the temp rise in engine temps is what your going to see between 7k and 7.4/7.5k. RPM will do that, especially as you go above 7k. The GT350 doesn’t just have coolers because it’s track intended - it’s also because the RPM.
Agreed, No shit. See the last 3 years of my posts from tracking a Whippled 2015. That car had substantial aero and cooling mods and ran 5w-30 while keeping the heads at 220F while putting 600rwhp down on track. It was a hoot!
 

sigintel

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low 200 diff temps are nothing to be concerned with, those CH temps are high though.
CHT will be addressed with TSTAT and aero.

My issue with the diff temps:
1. how fast it rises on track.
2. how fast it rises in just highway driving.

highway driving = 200 F
track = 260+ (if you can run 3 sessions at 90+ ambient)
Target is 220F track at 95F

Therefore:
Get highway diff temp down to 160F first, then test on track and see if it stays 215-230.

The fact that the diff is at 200F highway driving tells you there is already an issue.

In other words: there is no reason to go track the car to see if diff stays below 260 when I can use the highway driving temps as a target to reduce temperature rise above ambient.
 

PoppinJ

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The 2018 manual even states to run 5w30 on the track.
 

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Mountain376

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You can go ahead and shoot for getting significantly sub 200F diff oil temps, even on the street, but good luck without a cooler. The amount of fluid motion in that little space and all the continuous gear motion is going to generate heat and do so quickly. It is what it is. Honestly, Id shoot for 180 and be happy at 190 in 95F if you want a more realistic goal. But 200 may prove hard to improve.

Hey, it’s worth trying and seeing what delta you can obtain.

Also, if youre as worried about 200F oil temps on the street, I suggest you check the trans oil temp... because its likely more
 

FastCarFanBoy

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A Tstat won't do much if anything at all. It simply has no bearing on cooling capacity... it's a temperature operated check valve , nothing more. You may knock some temp off with aero, maybe 5 degrees, but you can only cram so much air into the radiator. At some point you just need more radiator and a good oil cooler.

I upgraded from a non-PP radiator to an aftermarket 3 row with a 170 tstat and temps only dropped about 10-15deg.
 

ddozier

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Also, if youre as worried about 200F oil temps on the street, I suggest you check the trans oil temp... because its likely more
I can tell you the trans temps increase at a faster rate than the rear end and peak out higher as well, Ford makes the air defector trans cooler for under the car but it is only marginally effective and is a hazard if you have lowered your ride height. The trans has a better chance of cooling via air movement since there is a larger surface area exposed to the moving air. The real fix is a dedicated cooler for both the trans and diff. While your at it add a LARGE oil cooler if you intend to run above 6800 RPM. The OEM oil cooler will quickly be overwhelmed if you regularly exceed 7000 rpm. Separating the oil cooler heat load from the coolant system is not a bad idea either for both systems.

A Tstat won't do much if anything at all. It simply has no bearing on cooling capacity... it's a temperature operated check valve , nothing more. You may knock some temp off with aero, maybe 5 degrees, but you can only cram so much air into the radiator. At some point you just need more radiator and a good oil cooler.

I upgraded from a non-PP radiator to an aftermarket 3 row with a 170 tstat and temps only dropped about 10-15deg.
The 170* stat will start the cooling process earlier but by your second lap any stat will be wide open anyway. I have the 170 stat in the car and with me running hard peak coolant temps are 202* @ 90* ambient. I have done extensive modifications to the radiator location, duct work in front of the radiator and hood venting to achieve this. The hood vents were the most effective at reducing coolant temps but were also added last in my testing. Hood vent dropped peak temps by 9* with no other changes. The OEM PP radiator is plenty large enough as long as you can maximize the airflow through the radiator.
 

sigintel

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A Tstat won't do much if anything at all. It simply has no bearing on cooling capacity... it's a temperature operated check valve , nothing more. You may knock some temp off with aero, maybe 5 degrees, but you can only cram so much air into the radiator. At some point you just need more radiator and a good oil cooler.

I upgraded from a non-PP radiator to an aftermarket 3 row with a 170 tstat and temps only dropped about 10-15deg.
Ahhh, correct .. kind of. You win a cold beer!
Thermostat design has a huge effect on cooling capacity. The ability to remove heat depends on flow of the mass of water, and flow of mass of air, and exchange of heat between them.

If you talking about a stock stat with same opening diameter and length, but modified to open at 170, then you are correct. If you are talking about Reische 170, it changes the max flow limit.
The 170 Reische has a larger opening when it does open. The fact that it provides less constriction to flow allows for more flow.
Completely removing tstat gets you even more flow.

Regarding aero, I wish you could come by. I am sure I could get you another 10F in 10 minutes of aero mods. Pull coping, weather strip, bat cover and lower grill.

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.

Prolly have some spare white hood vents to give you. Just dremel the back half open.

20% velocity (mass) airflow increase is same as 20% larger radiator. Ford gave us large rad and then massively restricted flow to decrease drag and underhood pressure.
 

sigintel

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Also, if youre as worried about 200F oil temps on the street, I suggest you check the trans oil temp... because its likely more
Already running trans cooler.
It held at 200-211, but I only needed two gears.
Will put a max size bar plate cooler in passenger fender longer term. Just not sure if I might use same circuit for diff cooling as well.
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