are you really running 75w140 in your rear axle
#1
01-03-2009, 05:14 PM
are you really running 75w140 in your rear axle
Seems extremely thick. Maybe I only think so because it was -40 this morning. But 140 that seems thick for anywhere. My truck is under warranty, so I dont want to do anything to not be able to get a warranty claim. I would just like to know what oil everbody is running (viscosity, brand name, ect). I am planning to change my oil soon. I have 17000kms and my rear axle coulor was grey!!??
Thanks form the north
KVFrider
Thanks form the north
KVFrider
#2
01-03-2009, 07:15 PM
Grayish color oil would lead me to think thats theres moisture in the differential. Normal used gear oil appears blackish. Does the oil smell burnt be any chance? Also as far as using different oil I'm sure ford designed it to use 75w140 that they recommend.
Its been cold here in Northern Minnesota too and i know my truck doesnt like moving in the cold weather lol. I plan on using Amsoil 75w140 in my differentials... just my .02
Its been cold here in Northern Minnesota too and i know my truck doesnt like moving in the cold weather lol. I plan on using Amsoil 75w140 in my differentials... just my .02
#3
01-03-2009, 07:58 PM
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#4
01-03-2009, 09:54 PM
#5
01-04-2009, 09:50 AM
Several things to remember here:
1) 75W140 synthetic (factory fill in Ford trucks for a few years now) has very good cold flow characteristics. You'll be fine overall. Could you be better? If -40 is very common where you are, see #3 below.
2) The grayish color is normal for the Ford truck factory fill oil (reputedly a Conoco product). Base oil is clear. Any color in the final product is from the additives and the dye. Yes, they use dye (Royal Purple, Amsoil green, Redline red etc.)
3) Can you get by with a lighter oil and how much difference will a lighter oil make? If you don't tow or haul and live in a generally cool climate, yes, you could get by with a 75W90 synthetic very well. The load trumps climate, so if you hal more than just short hops and short duration, stick withteh 75W140. How much difference would it make going from a 75W90 vs 75W140 (assuming a 75W140 syn and not a mineral SAE 140)? Negligible. Some studies I've see indicate UP TO only about 0.25 mpg between a 90 syn and a 140 syn. Not much gain there.
4) It's time to change that oil! It's full of break-in wear metals. Get it out of there! You'll find the magnet on the cover very fuzzy with swarf and metal dust. I was fairly appalled at how mine looked when I changed it at 10K miles. And yeah, my oil was that neutral gray as well. You second diff oil changed can be at 30 to 60K miles, depending on how youuse the truck (tow/haul a lit use the 30K)
1) 75W140 synthetic (factory fill in Ford trucks for a few years now) has very good cold flow characteristics. You'll be fine overall. Could you be better? If -40 is very common where you are, see #3 below.
2) The grayish color is normal for the Ford truck factory fill oil (reputedly a Conoco product). Base oil is clear. Any color in the final product is from the additives and the dye. Yes, they use dye (Royal Purple, Amsoil green, Redline red etc.)
3) Can you get by with a lighter oil and how much difference will a lighter oil make? If you don't tow or haul and live in a generally cool climate, yes, you could get by with a 75W90 synthetic very well. The load trumps climate, so if you hal more than just short hops and short duration, stick withteh 75W140. How much difference would it make going from a 75W90 vs 75W140 (assuming a 75W140 syn and not a mineral SAE 140)? Negligible. Some studies I've see indicate UP TO only about 0.25 mpg between a 90 syn and a 140 syn. Not much gain there.
4) It's time to change that oil! It's full of break-in wear metals. Get it out of there! You'll find the magnet on the cover very fuzzy with swarf and metal dust. I was fairly appalled at how mine looked when I changed it at 10K miles. And yeah, my oil was that neutral gray as well. You second diff oil changed can be at 30 to 60K miles, depending on how youuse the truck (tow/haul a lit use the 30K)
#7
01-04-2009, 10:53 AM
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#8
01-04-2009, 11:12 AM
Good question Ryan50hrl,
The manual out of my 2007 F-150 shows the front axle requires a change at 250 000kms. But it does not appear the rear axle has a specific interval. It says "Ford designed axles are lubricated for life. These lubricants are not to be changed unless service is required or the axle has been submerged in water".
I think like Jim Allen said I will be changing mine every 30-60 thousand kms.
The manual out of my 2007 F-150 shows the front axle requires a change at 250 000kms. But it does not appear the rear axle has a specific interval. It says "Ford designed axles are lubricated for life. These lubricants are not to be changed unless service is required or the axle has been submerged in water".
I think like Jim Allen said I will be changing mine every 30-60 thousand kms.
#9
01-04-2009, 01:32 PM
#10
01-04-2009, 08:29 PM
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Actually there is a big difference in the viscocity between 75-90 and 75-140 gear oil. The 90 & 140 refer to the time it takes a set amount of oil to flow through an orifice when the oil warm. The 75 refers to the same when the oil is cold. So changing to 75-90 gear oil will not gain much, if anything, when the differential is cold but it could lead to significant lubrication problems when warm.
#11
01-05-2009, 07:13 AM
I tow frequently with mine, but I'm not going to change it until ~50k miles. 60K powertrain warranty, and Ford telling me to never change it...knowing my luck I'd change it, have the axle fail on me, and have them deny the warranty claim because I changed it.....
#12
01-05-2009, 08:14 AM
First off the "90" and "140" are grade classifications, not viscosities in themselves. There are many ways to measure viscosity and one of the more commonly used gradations are Centistokes (cSt), which are a very fine measurement. To fit into a grade, the oil must fit between a specific range of viscosities set by the API (American Petroleum Institute), measured in cSt.
The commonly known summer API grades are 90 and 140 (but there's 250 too and a wide range of industrial ISO grades too). The “W grades (70W, 75W, 80W and 85W) refer to the oil’s cold flow characteristics and they are tested differently for that grade than with the summer grade.
There's actually a new summer grade that fits between 90 and 140, grade 110. The new API Grade 90 runs from 13.5 cSt to 18.50 cSt, 110 takes a little from the old grade 90, running from 18.50 to 24 cSt, and 140 now runs from 24 to 32 cSt. Many oils that were once a thick grade 90 or at the thin end of 140 will now be 110 grade oils technically. I believe the Ford 75W140 falls into that category now but has not yet been rated as such.
Sidenote: A grade 90 oil has the same viscosity in cSt as 40 to 50 grade engine oil.
Going back to temperature, the viscosity grades are all rated at 100 degrees Celsius, or 212F. What that means is that until the oil reaches 212 degrees, it will be thicker than it's rated viscosity. There are charts and calculators that can plot the viscosity of oils at various temps. Using one to compare some generic grade 90 and 140 oils (using the old API grades), we can plot the thickness of the oil at an “average” axle temp.
Let’s use 200F as an average. At 200 degrees, neither 90 or 140 have reached their rated viscosity. Using the chart I have handy, the generic 90 is at around 23 cSt and the grade 140 is at around 36 cSt (refer back to the grades above). The grade 90 is nearly in 140 viscosity and the 140 is mighty thick!
If you go up to 250 degrees, the 140 has thinned to around 13 cSt and the 90 has thinned to around 8.5 cSt. In essence, at 250 degrees, the 140 has thinned to about a 90 grade and the 90 is thinned to about the same grade as grade 30 engine oil. Many people think, and I agree, that you want a minimum of a 90 grade oil at any given temp the axle operates. The next question becomes, how hot does the axle oil get?
In general terms, axle oil temps are highly variable. There are some generalities. At any given load, a larger ring gear axle will run cooler than a smaller one because there are fewer/smaller teeth and the pressure is higher on each tooth, which tends to try to squeeze the oil out more. Small oil capacity is another factor with a smaller axle. Lower speeds generate lower temps and vice versa. Higher loads (including climbing hills) creates more heat. Also, generally, lower gears generate more heat than taller ones. That's pretty incremental but based on the info I've seen you might see a 10 degree average difference between a 3.07:1 ratio and a 4.10:1. High hypoid offset (pinion height) axles, like the 9 inch, will have higher temps than others. Most Ford integral axles have a 1.5-inch hypoid offset while the 9-inch is 2.38-in.
I have axle temp gauges on two trucks and have been watching them for years. I can't say my temps will be representative of every truck out there, but since one of them is an '05 F150, it might have some merit here.
Just "cruising" at 70, my rear axle temp runs about 160-180F on an 80-90 degree day with an unloaded truck. Slower speeds are cooler and it takes about 20 miles for the oil to reach full temp. With a load, a 7K trailer, axle temps run about 215-235F on a 80F day at 60 mph. Remember, mine is a 10.25 ring gear. A 9.75 or an 8.8 axle will generate somewhat more heat at any given load .
With gears, the viscosity is important for protecting the gears but when the viscosity isn't there, the oil also has anti-wear additives like sulfur and phosphorus (plus others like moly sometimes) so, short term, a drop in viscosity isn't immediately harmful if it’s not extreme (as would happen with 300 degree temps). The problem is that the additives wear out and they wear out faster with heat. An occasional temp spike won't hurt, but long-term high temps will kill the axle.
So, ultimately, picking the viscosity comes with knowing the heat generated in the axle. If you choose too thick an oil for the temp, you get poorer fuel economy due to fluid friction. Remember it takes 20 miles to heat that oil up to anything close to it’s rated temperature. Too thin an oil, may cause damage if the oil temp exceeds the rated temp.
In racing and some types of hard core 4-wheeling, shock loads come more into play, and here is where a thicker oil is king. The thicker oil acts as a “cushion” or “shock absorber” between the gear teeth. For most of us, temperature is the more important factor and if your oil is right for the temp, you’ll be adequately protected from shock loads.
Synthetic oils, with their very even molecular structure, tend to flow better at all temps, and reduce friction more, so at any given temperature range, the syn will flow a little better, have less drag and reduce friction more, vs a mineral oil. That’s why Ford, as strangled by CAFÉ regs as they are, can use a 140 grade in their trucks. The protection of a 140 with the low drag of a 90.
Another way to look at this is that if you keep a grade 90 cool, e.g. at or below it’s rated 212 degree temp, it will have all the protection you need. People often go to thicker oil in situations of high diff temps just to maintain the same protection as the 90 offers at the cooler temp (remember the example above). A method of cooling the oil has the same effect as a thicker oil.
Finned diff covers can reduce oil temps by around 15-20 degrees. (the Mag-Hytecs I put on my trucks knocks an honest 15+ degrees off).
The only way to know any of this for sure is by having a diff temp gauge hooked up. Some covers, (Mag-Hytec for one) have a bung in place for a sensor. AutoMeter makes bungs you can weld into an steel cover. If you tow or haul a lot, I’d high recommend a diff temp… if nothing else than to open your eyes. You'll also be surprised at how cool the axle runs in low speed, low load situations and how long it takes for the oil to warm up. These are the situations where a thick oil eats fuel from drag and fluid friction and where a lighter, especially a synthetic, will pay off. You will be surprised ay how much time your truck spends in this "inbetween" condition.
So, at the end of this diatribe, I can still say that a lightly used truck can go with a 75W90 syn (or an 85W-90 mineral) but a heavily used truck should go with a heavier grade oil as needed. The 75W140s are a good compromise because they offer superior protection without most of the added drag. I wouldn’t go with a 85W140 mineral oil unless I had to. It would be like honey half the time.
#13
01-08-2009, 07:49 PM
#14
01-09-2009, 08:24 PM
If you have a Ford factory Traction-Lok limited slip, it will be a clutch plate type, and you need the additive in virtually all plate style limited slips. Tha mount is accorign to the amount of oil in the diff. Look harder in your manual, I'll bet it's in there. My '05 manual mentions it.
If there is a gasket on the diff cover, it will not be reusable. Many times all they have is RTV sealant and no gasket. If it has RTV only, I recommend a gasket when you pull the cover, backed up by a light application of RTV.
If there is a gasket on the diff cover, it will not be reusable. Many times all they have is RTV sealant and no gasket. If it has RTV only, I recommend a gasket when you pull the cover, backed up by a light application of RTV.
#15
01-12-2021, 02:20 AM
Wondering if running 85w-140 would be much different than 75w-140...
Oh, sure, there's a difference in viscosity between grade 90 and grade 140 but the defining line between needing a grade 90 and a grade 140 is heat.
First off the "90" and "140" are grade classifications, not viscosities in themselves. There are many ways to measure viscosity and one of the more commonly used gradations are Centistokes (cSt), which are a very fine measurement. To fit into a grade, the oil must fit between a specific range of viscosities set by the API (American Petroleum Institute), measured in cSt.
The commonly known summer API grades are 90 and 140 (but there's 250 too and a wide range of industrial ISO grades too). The “W grades (70W, 75W, 80W and 85W) refer to the oil’s cold flow characteristics and they are tested differently for that grade than with the summer grade.
There's actually a new summer grade that fits between 90 and 140, grade 110. The new API Grade 90 runs from 13.5 cSt to 18.50 cSt, 110 takes a little from the old grade 90, running from 18.50 to 24 cSt, and 140 now runs from 24 to 32 cSt. Many oils that were once a thick grade 90 or at the thin end of 140 will now be 110 grade oils technically. I believe the Ford 75W140 falls into that category now but has not yet been rated as such.
Sidenote: A grade 90 oil has the same viscosity in cSt as 40 to 50 grade engine oil.
Going back to temperature, the viscosity grades are all rated at 100 degrees Celsius, or 212F. What that means is that until the oil reaches 212 degrees, it will be thicker than it's rated viscosity. There are charts and calculators that can plot the viscosity of oils at various temps. Using one to compare some generic grade 90 and 140 oils (using the old API grades), we can plot the thickness of the oil at an “average” axle temp.
Let’s use 200F as an average. At 200 degrees, neither 90 or 140 have reached their rated viscosity. Using the chart I have handy, the generic 90 is at around 23 cSt and the grade 140 is at around 36 cSt (refer back to the grades above). The grade 90 is nearly in 140 viscosity and the 140 is mighty thick!
If you go up to 250 degrees, the 140 has thinned to around 13 cSt and the 90 has thinned to around 8.5 cSt. In essence, at 250 degrees, the 140 has thinned to about a 90 grade and the 90 is thinned to about the same grade as grade 30 engine oil. Many people think, and I agree, that you want a minimum of a 90 grade oil at any given temp the axle operates. The next question becomes, how hot does the axle oil get?
In general terms, axle oil temps are highly variable. There are some generalities. At any given load, a larger ring gear axle will run cooler than a smaller one because there are fewer/smaller teeth and the pressure is higher on each tooth, which tends to try to squeeze the oil out more. Small oil capacity is another factor with a smaller axle. Lower speeds generate lower temps and vice versa. Higher loads (including climbing hills) creates more heat. Also, generally, lower gears generate more heat than taller ones. That's pretty incremental but based on the info I've seen you might see a 10 degree average difference between a 3.07:1 ratio and a 4.10:1. High hypoid offset (pinion height) axles, like the 9 inch, will have higher temps than others. Most Ford integral axles have a 1.5-inch hypoid offset while the 9-inch is 2.38-in.
I have axle temp gauges on two trucks and have been watching them for years. I can't say my temps will be representative of every truck out there, but since one of them is an '05 F150, it might have some merit here.
Just "cruising" at 70, my rear axle temp runs about 160-180F on an 80-90 degree day with an unloaded truck. Slower speeds are cooler and it takes about 20 miles for the oil to reach full temp. With a load, a 7K trailer, axle temps run about 215-235F on a 80F day at 60 mph. Remember, mine is a 10.25 ring gear. A 9.75 or an 8.8 axle will generate somewhat more heat at any given load .
With gears, the viscosity is important for protecting the gears but when the viscosity isn't there, the oil also has anti-wear additives like sulfur and phosphorus (plus others like moly sometimes) so, short term, a drop in viscosity isn't immediately harmful if it’s not extreme (as would happen with 300 degree temps). The problem is that the additives wear out and they wear out faster with heat. An occasional temp spike won't hurt, but long-term high temps will kill the axle.
So, ultimately, picking the viscosity comes with knowing the heat generated in the axle. If you choose too thick an oil for the temp, you get poorer fuel economy due to fluid friction. Remember it takes 20 miles to heat that oil up to anything close to it’s rated temperature. Too thin an oil, may cause damage if the oil temp exceeds the rated temp.
In racing and some types of hard core 4-wheeling, shock loads come more into play, and here is where a thicker oil is king. The thicker oil acts as a “cushion” or “shock absorber” between the gear teeth. For most of us, temperature is the more important factor and if your oil is right for the temp, you’ll be adequately protected from shock loads.
Synthetic oils, with their very even molecular structure, tend to flow better at all temps, and reduce friction more, so at any given temperature range, the syn will flow a little better, have less drag and reduce friction more, vs a mineral oil. That’s why Ford, as strangled by CAFÉ regs as they are, can use a 140 grade in their trucks. The protection of a 140 with the low drag of a 90.
Another way to look at this is that if you keep a grade 90 cool, e.g. at or below it’s rated 212 degree temp, it will have all the protection you need. People often go to thicker oil in situations of high diff temps just to maintain the same protection as the 90 offers at the cooler temp (remember the example above). A method of cooling the oil has the same effect as a thicker oil.
Finned diff covers can reduce oil temps by around 15-20 degrees. (the Mag-Hytecs I put on my trucks knocks an honest 15+ degrees off).
The only way to know any of this for sure is by having a diff temp gauge hooked up. Some covers, (Mag-Hytec for one) have a bung in place for a sensor. AutoMeter makes bungs you can weld into an steel cover. If you tow or haul a lot, I’d high recommend a diff temp… if nothing else than to open your eyes. You'll also be surprised at how cool the axle runs in low speed, low load situations and how long it takes for the oil to warm up. These are the situations where a thick oil eats fuel from drag and fluid friction and where a lighter, especially a synthetic, will pay off. You will be surprised ay how much time your truck spends in this "inbetween" condition.
So, at the end of this diatribe, I can still say that a lightly used truck can go with a 75W90 syn (or an 85W-90 mineral) but a heavily used truck should go with a heavier grade oil as needed. The 75W140s are a good compromise because they offer superior protection without most of the added drag. I wouldn’t go with a 85W140 mineral oil unless I had to. It would be like honey half the time.
First off the "90" and "140" are grade classifications, not viscosities in themselves. There are many ways to measure viscosity and one of the more commonly used gradations are Centistokes (cSt), which are a very fine measurement. To fit into a grade, the oil must fit between a specific range of viscosities set by the API (American Petroleum Institute), measured in cSt.
The commonly known summer API grades are 90 and 140 (but there's 250 too and a wide range of industrial ISO grades too). The “W grades (70W, 75W, 80W and 85W) refer to the oil’s cold flow characteristics and they are tested differently for that grade than with the summer grade.
There's actually a new summer grade that fits between 90 and 140, grade 110. The new API Grade 90 runs from 13.5 cSt to 18.50 cSt, 110 takes a little from the old grade 90, running from 18.50 to 24 cSt, and 140 now runs from 24 to 32 cSt. Many oils that were once a thick grade 90 or at the thin end of 140 will now be 110 grade oils technically. I believe the Ford 75W140 falls into that category now but has not yet been rated as such.
Sidenote: A grade 90 oil has the same viscosity in cSt as 40 to 50 grade engine oil.
Going back to temperature, the viscosity grades are all rated at 100 degrees Celsius, or 212F. What that means is that until the oil reaches 212 degrees, it will be thicker than it's rated viscosity. There are charts and calculators that can plot the viscosity of oils at various temps. Using one to compare some generic grade 90 and 140 oils (using the old API grades), we can plot the thickness of the oil at an “average” axle temp.
Let’s use 200F as an average. At 200 degrees, neither 90 or 140 have reached their rated viscosity. Using the chart I have handy, the generic 90 is at around 23 cSt and the grade 140 is at around 36 cSt (refer back to the grades above). The grade 90 is nearly in 140 viscosity and the 140 is mighty thick!
If you go up to 250 degrees, the 140 has thinned to around 13 cSt and the 90 has thinned to around 8.5 cSt. In essence, at 250 degrees, the 140 has thinned to about a 90 grade and the 90 is thinned to about the same grade as grade 30 engine oil. Many people think, and I agree, that you want a minimum of a 90 grade oil at any given temp the axle operates. The next question becomes, how hot does the axle oil get?
In general terms, axle oil temps are highly variable. There are some generalities. At any given load, a larger ring gear axle will run cooler than a smaller one because there are fewer/smaller teeth and the pressure is higher on each tooth, which tends to try to squeeze the oil out more. Small oil capacity is another factor with a smaller axle. Lower speeds generate lower temps and vice versa. Higher loads (including climbing hills) creates more heat. Also, generally, lower gears generate more heat than taller ones. That's pretty incremental but based on the info I've seen you might see a 10 degree average difference between a 3.07:1 ratio and a 4.10:1. High hypoid offset (pinion height) axles, like the 9 inch, will have higher temps than others. Most Ford integral axles have a 1.5-inch hypoid offset while the 9-inch is 2.38-in.
I have axle temp gauges on two trucks and have been watching them for years. I can't say my temps will be representative of every truck out there, but since one of them is an '05 F150, it might have some merit here.
Just "cruising" at 70, my rear axle temp runs about 160-180F on an 80-90 degree day with an unloaded truck. Slower speeds are cooler and it takes about 20 miles for the oil to reach full temp. With a load, a 7K trailer, axle temps run about 215-235F on a 80F day at 60 mph. Remember, mine is a 10.25 ring gear. A 9.75 or an 8.8 axle will generate somewhat more heat at any given load .
With gears, the viscosity is important for protecting the gears but when the viscosity isn't there, the oil also has anti-wear additives like sulfur and phosphorus (plus others like moly sometimes) so, short term, a drop in viscosity isn't immediately harmful if it’s not extreme (as would happen with 300 degree temps). The problem is that the additives wear out and they wear out faster with heat. An occasional temp spike won't hurt, but long-term high temps will kill the axle.
So, ultimately, picking the viscosity comes with knowing the heat generated in the axle. If you choose too thick an oil for the temp, you get poorer fuel economy due to fluid friction. Remember it takes 20 miles to heat that oil up to anything close to it’s rated temperature. Too thin an oil, may cause damage if the oil temp exceeds the rated temp.
In racing and some types of hard core 4-wheeling, shock loads come more into play, and here is where a thicker oil is king. The thicker oil acts as a “cushion” or “shock absorber” between the gear teeth. For most of us, temperature is the more important factor and if your oil is right for the temp, you’ll be adequately protected from shock loads.
Synthetic oils, with their very even molecular structure, tend to flow better at all temps, and reduce friction more, so at any given temperature range, the syn will flow a little better, have less drag and reduce friction more, vs a mineral oil. That’s why Ford, as strangled by CAFÉ regs as they are, can use a 140 grade in their trucks. The protection of a 140 with the low drag of a 90.
Another way to look at this is that if you keep a grade 90 cool, e.g. at or below it’s rated 212 degree temp, it will have all the protection you need. People often go to thicker oil in situations of high diff temps just to maintain the same protection as the 90 offers at the cooler temp (remember the example above). A method of cooling the oil has the same effect as a thicker oil.
Finned diff covers can reduce oil temps by around 15-20 degrees. (the Mag-Hytecs I put on my trucks knocks an honest 15+ degrees off).
The only way to know any of this for sure is by having a diff temp gauge hooked up. Some covers, (Mag-Hytec for one) have a bung in place for a sensor. AutoMeter makes bungs you can weld into an steel cover. If you tow or haul a lot, I’d high recommend a diff temp… if nothing else than to open your eyes. You'll also be surprised at how cool the axle runs in low speed, low load situations and how long it takes for the oil to warm up. These are the situations where a thick oil eats fuel from drag and fluid friction and where a lighter, especially a synthetic, will pay off. You will be surprised ay how much time your truck spends in this "inbetween" condition.
So, at the end of this diatribe, I can still say that a lightly used truck can go with a 75W90 syn (or an 85W-90 mineral) but a heavily used truck should go with a heavier grade oil as needed. The 75W140s are a good compromise because they offer superior protection without most of the added drag. I wouldn’t go with a 85W140 mineral oil unless I had to. It would be like honey half the time.