Do differentials run HOT?
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It will be HOT. NO you can't keep your hand on it for long....
If you can't hold your hand on it
It's over 140°F.......
It's over 140°F.......
i dont know what kind of diffies you guys have (maybe some inefficent heat producing kind?) but my old subaru's diff never got above 120f. i was awalys able to keep a hand on it without getting too hot even after 90mph cruises.
Dana's get hot. Before I was an Amsoil guy I was running Redline....and it was very hot with Redline...some Dana's have cooling fins....
diffs get extremely hot when breaking in the gear set, hot enough to damage ARB locker seals if driven long distances on new gears
my LX450's diffs only get luke warm after my 30 mile freeway commute, it has 110K on the original gears front and rear
my LX450's diffs only get luke warm after my 30 mile freeway commute, it has 110K on the original gears front and rear
The temps of the differential depends on the load and the horsepower.
Yup, about 3 or 4% of the power going into the differential gets converted to heat. Cruising down the highway using 40 hp makes a lot less heat than a WFO run.
MolaKule
Staff member
FWIW
I checked the temperature on the differential of my wife's Nissan PathFinder diffy last night when she arrived home:
1. Ambient temp - 99 F
2. Diffy case temp - 140 F.
3. Driven at 75+ mph for 47 miles.
GL was a proprietary 75W90 GL5.
I checked the temperature on the differential of my wife's Nissan PathFinder diffy last night when she arrived home:
1. Ambient temp - 99 F
2. Diffy case temp - 140 F.
3. Driven at 75+ mph for 47 miles.
GL was a proprietary 75W90 GL5.
mola - would consider that warm but not fusion warm
40 * .04 = 1.6
1.6 * 746 = 1193.6 watts
It's like an 1193.6 watt space heater inside the differential.
Although I thought the HP figures for highway cruising were more on the order of 10-15HP.
MolaKule
Staff member
FWIW
I checked the temperature of the differential on my Nissan Frontier diffy tonight when I arrived home:
1. Ambient temp - 101 F
2. Diffy case temp - 158 F.
3. Driven at 75+ mph for 42 miles.
GL was a proprietary 75W90 GL5. Temp taken using RS Infrared Temp sensor.
I checked the temperature of the differential on my Nissan Frontier diffy tonight when I arrived home:
1. Ambient temp - 101 F
2. Diffy case temp - 158 F.
3. Driven at 75+ mph for 42 miles.
GL was a proprietary 75W90 GL5. Temp taken using RS Infrared Temp sensor.
Depends on the car and how fast you cruise
I think 100 lb force to move a car down the road is fairly low for the smallish average car.
At 60 mph = 88 ft/sec
100lb x 88 ft/sec = 8800 ftlb/sec
1 hp = 550 ft lb/sec
8800/550 = 16 hp Assuming a drive train efficiency of 85%, that = 18.8 hp at the flywheel.
But that's too close to your estimate
Power is roughly proportional to the cube of the speed. This is pretty accurate for small speed changes.
Lets try 70 mph
18.8 x (70/60)^3 = 29.86 hp. Close enough to my guess
I was searching for information on temp's for a differential.
I checked the rear differential in my Cressida today after a 100 mile run at 75mph. I check the case several times with my infrared gun and got readings of around 180-185F. Ambiant temp was about 80F.
I didn't know the differential would produce that much heat and I am running Shaffers #267.
I have been considering having my pinion bearings looked at as I do get a slight whinning noise from the rear end now. Is this a temp. a further sign of worn bearings or is that a reasonable temp. ?
I checked the rear differential in my Cressida today after a 100 mile run at 75mph. I check the case several times with my infrared gun and got readings of around 180-185F. Ambiant temp was about 80F.
I didn't know the differential would produce that much heat and I am running Shaffers #267.
I have been considering having my pinion bearings looked at as I do get a slight whinning noise from the rear end now. Is this a temp. a further sign of worn bearings or is that a reasonable temp. ?
"I didn't know the differential would produce that much heat and I am running Shaffers #267."
MolaKule
Staff member
Cressida,
Run some 75W140 and see what happens.
Run some 75W140 and see what happens.
diff design has a lot to do with it as well. The more hypoid it is, the more heat generated.
Spiral bevel designs generate a lot less heat (pinion on the centre line of the crown wheel)
I'll take some temp readings off my front and rear diffs tonight (Land Rover Defender, constant 4wd, front diff spiral bevel, rear hypoid design])
Spiral bevel designs generate a lot less heat (pinion on the centre line of the crown wheel)
I'll take some temp readings off my front and rear diffs tonight (Land Rover Defender, constant 4wd, front diff spiral bevel, rear hypoid design])
Look for a story in Four Wheeler's July issue (appearing in early June) that will detail the particulars of some tests we did on my truck in a towing situation. Speed, load, hypoid offset, bearing preloads all are factors and each model of diff is different. The lubricant can bring down the temp dramatically, as we learned, by reducing friction. High capacity covers are also a benifit. I actually subjected my truck to a 34,000 pound towed load in these tests!
Tease! =-)
What sort of temperatures where initially recorded?
Alex.
What sort of temperatures where initially recorded?
Alex.
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