"Rear Axle Differential Temp Increased, Decrease Speed" warning

[GTP]

...and perhaps maybe wrap a foot forward from the diff, to prevent a bit of extra heat dissipation from flowing over stuff.

3 rolls can cover what I think is required - if you have the diff as the goal.

John, bottom line it for me. What width and length of wrap should I order if I just want to wrap the exhaust pipes around the differential?

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[NightmareMoon]

One 25ft roll on each side will go from the exhaust hangers to the front of the diff. Thats what I did earlier in the week.

FWIW, after you get some heat into the exhaust, the temps on the wrapped section are a lot higher than the surface temps on the unwrapped pipe. Thats to be expected I guess when wrapping something with insulation. I'm hoping the wrap has less radiative heat even if the surface temps are actually higher.

 

[Wally-Bob]

Also turning on Track Mode doesn't entirely disable all of the 'traction control' features. To entirely disable AdvanceTrac (yaw) and Traction Control (rear wheel traction) you need to hold the traction control button down for like 5-8 seconds (second button from the left on the premium cars). Just using the mode button to put the car in Track mode doesn't turn it all off, FWIW.

Adding this just in case someone out there doesn't already know...

One must wait for the notification on the dash "Advance Track Off" to appear to ensure that it is completely off. I've heard of different times quoted, I need to hold my toggle up for 12-14 seconds for the message to appear. Be aware that you need to do this every time you restart the engine because by default it resets to "Advance Track On".

 

[Wally-Bob]

FWIW, after you get some heat into the exhaust, the temps on the wrapped section are a lot higher than the surface temps on the unwrapped pipe. Thats to be expected I guess when wrapping something with insulation. I'm hoping the wrap has less radiative heat even if the surface temps are actually higher.

NightmareMoon,

From what I’ve heard, SUPPOSIBLY you can touch the wrap during operation without your skin sticking to it. (severe burns) So that indicates positive results as far as radiant heat reaching the differential from the exhaust pipes it “nests” in. I suspect this is a significant factor for the heating of the differential. The major factor of course is gear friction.

Earlier in the thread there were discussions regarding wrapping the entire system including headers. While there are advantages for under hood temps… a cold air intake is intended to abate this. A thought about this is it may be a path of diminishing returns and perhaps may even have negative returns. The purpose of headers is to increase HP output by reducing the fluid HP required to pump the exhaust out of the tail pipe. Pumping pressure increases exponentially as velocity increases. Obviously as we know, the larger pipe size of the header primary tubes helps this by reducing the velocity of the exhaust gas. Cooling the exhaust gas also reduces the velocity thus fluid HP pumping requirements. What may not be so obvious to many is that the cooling effect of exhaust gas by headers is a significant component of the entire performance gain picture.

Similarly, exhaust gas cooling occurs at the cats, down pipes, X or H pipe. But these are upstream of the diff so there is hot air from these components traveling down the transmission tunnel towards the diff. However this hot air mixes with ambient air and is significantly cooled, especially at speed.

My point here is I intend to insulate starting immediately after my X pipe clamps and proceed downstream to a point after the differential where the pipes bend outward.

I gratefully thank GT_Roadcourse_Newb for the wrap idea and the great Pics.

Does anyone have favorable results from wrapping yet?

 

[mbeale68]

I ran three 20 minute sessions at Thunderhill without any issues on Friday. This was a 100 degree day. My engine oil got close to the yellow zone on the digital gage, but I didn't get a differential temperature warning. I was running with stability control and traction control on and am not very fast yet. Car is stock except for RE71R tires (275 35R19/285 35R19) and an extra degree of negative camber at the front.

 

[jhols]

I ran three 20 minute sessions at Thunderhill without any issues on Friday. This was a 100 degree day. My engine oil got close to the yellow zone on the digital gage, but I didn't get a differential temperature warning. I was running with stability control and traction control on and am not very fast yet. Car is stock except for RE71R tires (275 35R19/285 35R19) and an extra degree of negative camber at the front.

How did the bridgestones hold up to track duty?

 

[mbeale68]

The RE71Rs seemed to hold up pretty well.

What are the current thoughts on how traction/stability control affect the differential temperature? I would think that traction control off might be worse, because with it off there could be larger differences in speed between the two rear wheels and thus more heat build up in the differential.

 

[EXP Jawa]

I think that the differential's contribution to axle temp isn't as significant as you think. Under normal conditions, the normal differential rate from side to side is only on the order of 10-20 RPM, and it only does that while turning. The amount of friction sliding that occurs is pretty low. With a differential like the Torsen, the amount of lock up is proportional to input torque, so when driving under high-torque (to the axle) conditions, the differential prevents a lot of differentiation from occurring, even when cornering. This isn't as true for the Traction Lock, however, as its bias threshold is lower and its lock up is driven by the preload springs, not input torque.

Far and away, the biggest contribution to axle temp (within the axle) is the ring & pinion, since its constantly under high torque, and hypoid gear meshing has a lot of sliding friction in it. This is especially true for a newish gear. And, of course as has been addresses previously, having the exhaust radiating heat in close proximity is a big factor too. The differential, and how its impacted by traction control, notsomuch.

 

[Optimum Performance]

[MENTION=21967]mbeale68[/MENTION] Do you have a Performance Pack? If not what gear ratio?

 

[Bahndvr]

Rick,
What is the Torque Bias Ratio of the Torsen?

 

[EXP Jawa]

It's approximately 2.7:1 in the factory configuration, in Ford Gen-3 lube with friction modifier. However, it would be around 3:1 with a straight 80W90 w/o modifier, though I'd be obligated to tell you that changing the oil at all will give fits to the engineers that specced out the oil seals in the system. A lot of people disregard the fact that the plastics used in them can be sensitive to different oil formulas, so on your own heads be it if you get a leak... I have no good way to know where the TBR would be in various other popular lubricants without testing; both the specific weight and additive package in the oil has impact on TBR level and performance over life.

 

[mbeale68]

Yes I have the performance package. (Thought that was in my profile, will have to update it.)

 

[Bahndvr]

Rick,
Is the Ford Gen-3 a SAE 75W-85 Synthetic Hypoid Gear Lubricant?

 

[EXP Jawa]

Rick,
Is the Ford Gen-3 a SAE 75W-85 Synthetic Hypoid Gear Lubricant?

Yes, the Gen-3 is 75W85, which, combined with FM is a fairly low-friction lube.

 

[Bahndvr]

Not trying to highjack the thread but I think that if a easy and inexpensive solution could be found we would all be happy.

So Rick,
I have heard that due to the properties of FM that it doesn't dissipate heat very well (and this may be false). So if we don't run FM wouldn't the diff have a better opportunity to cool? Your thoughts?

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