Anybody done this and any problems?
From 80/85W140 to 75W110 in LSD in tow vehice?
- Thread starter sprintman
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Seems risky.
No, usually switch the other way in SUV applications.
Depends on how it's used and what the axle oil temp might be.
Protection comes down to boundary and film lubrication. The boundary side come from the additives and most good gear oils have that, regardless of viscosity. The film strength comes from the fluid and its viscosity.
Gear oil viscosity grade is rated at 212F, just like motor oil. If the oil temp is higher than 212F by some margin, the oil is thinner than grade. If the oil is cooler, it will be thicker. My truck solo runs at about 170F on a 90F day with 90 grade oil. At that temp, the oil is running in 140 grade territory. Conversely, if I were to get the temp up to 250F, the oil has thinned below grade (around a 75 grade according to the viscosity calculator I use). All this is why I run diff oil temp gauges on my trucks and choose viscosity based on that. The way I use the truck, diff temp seldom even gets to 212, much less over that.
You already have the protection of the additives regardless of the oil and gear oils do rely A LOT on the additives but you don't want to rely on them exclusively. If you diff is always running below 212F, you are certainly wasting energy with a 140 and maybe even a 110. Rolling resistance can be reduced significantly by reducing gear oil viscosity but it's counter productive if you need more protection. The goal I set is that at whatever maximum temp my diff oil runs, the gear oil does not fall out of the 90 grade viscosity range. Going back to 250F gear oil temps, a 40 grade is running at the low end of 90 grade at that temp (varies some according to the actual oil, but that's an average I have fond running several brands thru the calculator).
I guess what I'm sayin in a long winded way... if you want to make an educated choice, install a diff temp gauge. Otherwise, err on the side oc=f caution. Also, some folks will use a infrared temp gun on the diff cover. I have compared my gun to what the gauge said and it's pretty close... running about 25 deg less than the gauge (on my gun). Go out and tow at your max and run several hours to get the oil up to max temp. find a good spot where you can whip off the road fast and leap out to check the diff(s) el rapido. Will give you some idea of the temps.
BTW, another way to be able to run a thinner oil for more efficiency without overheating the oil is to run a fined cover. More capacity doesn't by itself reduce oil temp (though it does dampen temp spikes and slow the rate of temp rise) but a finned, high capacity cover has more surface area for cooling. In my own case, such a cover reduced max oil temps by ~15-20F and that's one reason why I can run 90 grade and still tow 10K pounds while staying under 220F. I occasionally see some spikes higher but in the areas I go that is very seldom, of short duration and never over 240.
Protection comes down to boundary and film lubrication. The boundary side come from the additives and most good gear oils have that, regardless of viscosity. The film strength comes from the fluid and its viscosity.
Gear oil viscosity grade is rated at 212F, just like motor oil. If the oil temp is higher than 212F by some margin, the oil is thinner than grade. If the oil is cooler, it will be thicker. My truck solo runs at about 170F on a 90F day with 90 grade oil. At that temp, the oil is running in 140 grade territory. Conversely, if I were to get the temp up to 250F, the oil has thinned below grade (around a 75 grade according to the viscosity calculator I use). All this is why I run diff oil temp gauges on my trucks and choose viscosity based on that. The way I use the truck, diff temp seldom even gets to 212, much less over that.
You already have the protection of the additives regardless of the oil and gear oils do rely A LOT on the additives but you don't want to rely on them exclusively. If you diff is always running below 212F, you are certainly wasting energy with a 140 and maybe even a 110. Rolling resistance can be reduced significantly by reducing gear oil viscosity but it's counter productive if you need more protection. The goal I set is that at whatever maximum temp my diff oil runs, the gear oil does not fall out of the 90 grade viscosity range. Going back to 250F gear oil temps, a 40 grade is running at the low end of 90 grade at that temp (varies some according to the actual oil, but that's an average I have fond running several brands thru the calculator).
I guess what I'm sayin in a long winded way... if you want to make an educated choice, install a diff temp gauge. Otherwise, err on the side oc=f caution. Also, some folks will use a infrared temp gun on the diff cover. I have compared my gun to what the gauge said and it's pretty close... running about 25 deg less than the gauge (on my gun). Go out and tow at your max and run several hours to get the oil up to max temp. find a good spot where you can whip off the road fast and leap out to check the diff(s) el rapido. Will give you some idea of the temps.
BTW, another way to be able to run a thinner oil for more efficiency without overheating the oil is to run a fined cover. More capacity doesn't by itself reduce oil temp (though it does dampen temp spikes and slow the rate of temp rise) but a finned, high capacity cover has more surface area for cooling. In my own case, such a cover reduced max oil temps by ~15-20F and that's one reason why I can run 90 grade and still tow 10K pounds while staying under 220F. I occasionally see some spikes higher but in the areas I go that is very seldom, of short duration and never over 240.
MolaKule
Staff member
Most of those diffy specs are based on the use of mineral oil fluids.
I would say if you are running a full synthetic 75W110 (like Amsoil SVG or the LE product) then go for it as it has the GL-5 protection package and should run a smidgeon cooler since the base oil viscosity is slightly lower.
I would start a baseline VOA/UOA before changing to also determine if there is any change in wear trends.
As Jim stated, run heat measurements before and after fluid change along with your VOA/UOAs and let us know how it works out.
I would say if you are running a full synthetic 75W110 (like Amsoil SVG or the LE product) then go for it as it has the GL-5 protection package and should run a smidgeon cooler since the base oil viscosity is slightly lower.
I would start a baseline VOA/UOA before changing to also determine if there is any change in wear trends.
As Jim stated, run heat measurements before and after fluid change along with your VOA/UOAs and let us know how it works out.
Originally Posted By: Jim Allen
BTW, another way to be able to run a thinner oil for more efficiency without overheating the oil is to run a fined cover. More capacity doesn't by itself reduce oil temp (though it does dampen temp spikes and slow the rate of temp rise) but a finned, high capacity cover has more surface area for cooling. In my own case, such a cover reduced max oil temps by ~15-20F and that's one reason why I can run 90 grade and still tow 10K pounds while staying under 220F. I occasionally see some spikes higher but in the areas I go that is very seldom, of short duration and never over 240.
I went the other way (xW-90 to 80W-140) purely as the rear diff now sports an 8mm nodular iron cover and so won't dissipate heat near as effectively as the original tin cover.
I'm not sure I really want to know how hot the diff gets now, it would take skin off my thermally calibrated finger when it was still only using a tin cover.
Remember also that the more heavily hypoid a crown wheel is the more heat generated.
A centreline spiral bevel design runs significantly cooler than something like a Dana 60 or Ford 9".
Steve, what car ?
Ford and Holden spec 80W-140 as the Dana diffs are smallish with lots of torque going through them.
They also seem prone to bearing wear too.
BTW, another way to be able to run a thinner oil for more efficiency without overheating the oil is to run a fined cover. More capacity doesn't by itself reduce oil temp (though it does dampen temp spikes and slow the rate of temp rise) but a finned, high capacity cover has more surface area for cooling. In my own case, such a cover reduced max oil temps by ~15-20F and that's one reason why I can run 90 grade and still tow 10K pounds while staying under 220F. I occasionally see some spikes higher but in the areas I go that is very seldom, of short duration and never over 240.
I went the other way (xW-90 to 80W-140) purely as the rear diff now sports an 8mm nodular iron cover and so won't dissipate heat near as effectively as the original tin cover.
I'm not sure I really want to know how hot the diff gets now, it would take skin off my thermally calibrated finger when it was still only using a tin cover.
Remember also that the more heavily hypoid a crown wheel is the more heat generated.
A centreline spiral bevel design runs significantly cooler than something like a Dana 60 or Ford 9".
Steve, what car ?
Ford and Holden spec 80W-140 as the Dana diffs are smallish with lots of torque going through them.
They also seem prone to bearing wear too.
Originally Posted By: Jim Allen
Depends on how it's used and what the axle oil temp might be.
Protection comes down to boundary and film lubrication. The boundary side come from the additives and most good gear oils have that, regardless of viscosity. The film strength comes from the fluid and its viscosity.
Gear oil viscosity grade is rated at 212F, just like motor oil. If the oil temp is higher than 212F by some margin, the oil is thinner than grade. If the oil is cooler, it will be thicker. My truck solo runs at about 170F on a 90F day with 90 grade oil. At that temp, the oil is running in 140 grade territory. Conversely, if I were to get the temp up to 250F, the oil has thinned below grade (around a 75 grade according to the viscosity calculator I use). All this is why I run diff oil temp gauges on my trucks and choose viscosity based on that. The way I use the truck, diff temp seldom even gets to 212, much less over that.
You already have the protection of the additives regardless of the oil and gear oils do rely A LOT on the additives but you don't want to rely on them exclusively. If you diff is always running below 212F, you are certainly wasting energy with a 140 and maybe even a 110. Rolling resistance can be reduced significantly by reducing gear oil viscosity but it's counter productive if you need more protection. The goal I set is that at whatever maximum temp my diff oil runs, the gear oil does not fall out of the 90 grade viscosity range. Going back to 250F gear oil temps, a 40 grade is running at the low end of 90 grade at that temp (varies some according to the actual oil, but that's an average I have fond running several brands thru the calculator).
I guess what I'm sayin in a long winded way... if you want to make an educated choice, install a diff temp gauge. Otherwise, err on the side oc=f caution. Also, some folks will use a infrared temp gun on the diff cover. I have compared my gun to what the gauge said and it's pretty close... running about 25 deg less than the gauge (on my gun). Go out and tow at your max and run several hours to get the oil up to max temp. find a good spot where you can whip off the road fast and leap out to check the diff(s) el rapido. Will give you some idea of the temps.
BTW, another way to be able to run a thinner oil for more efficiency without overheating the oil is to run a fined cover. More capacity doesn't by itself reduce oil temp (though it does dampen temp spikes and slow the rate of temp rise) but a finned, high capacity cover has more surface area for cooling. In my own case, such a cover reduced max oil temps by ~15-20F and that's one reason why I can run 90 grade and still tow 10K pounds while staying under 220F. I occasionally see some spikes higher but in the areas I go that is very seldom, of short duration and never over 240.
The best response to a question I've seen here, and I've been here since day one. Many thanks
Depends on how it's used and what the axle oil temp might be.
Protection comes down to boundary and film lubrication. The boundary side come from the additives and most good gear oils have that, regardless of viscosity. The film strength comes from the fluid and its viscosity.
Gear oil viscosity grade is rated at 212F, just like motor oil. If the oil temp is higher than 212F by some margin, the oil is thinner than grade. If the oil is cooler, it will be thicker. My truck solo runs at about 170F on a 90F day with 90 grade oil. At that temp, the oil is running in 140 grade territory. Conversely, if I were to get the temp up to 250F, the oil has thinned below grade (around a 75 grade according to the viscosity calculator I use). All this is why I run diff oil temp gauges on my trucks and choose viscosity based on that. The way I use the truck, diff temp seldom even gets to 212, much less over that.
You already have the protection of the additives regardless of the oil and gear oils do rely A LOT on the additives but you don't want to rely on them exclusively. If you diff is always running below 212F, you are certainly wasting energy with a 140 and maybe even a 110. Rolling resistance can be reduced significantly by reducing gear oil viscosity but it's counter productive if you need more protection. The goal I set is that at whatever maximum temp my diff oil runs, the gear oil does not fall out of the 90 grade viscosity range. Going back to 250F gear oil temps, a 40 grade is running at the low end of 90 grade at that temp (varies some according to the actual oil, but that's an average I have fond running several brands thru the calculator).
I guess what I'm sayin in a long winded way... if you want to make an educated choice, install a diff temp gauge. Otherwise, err on the side oc=f caution. Also, some folks will use a infrared temp gun on the diff cover. I have compared my gun to what the gauge said and it's pretty close... running about 25 deg less than the gauge (on my gun). Go out and tow at your max and run several hours to get the oil up to max temp. find a good spot where you can whip off the road fast and leap out to check the diff(s) el rapido. Will give you some idea of the temps.
BTW, another way to be able to run a thinner oil for more efficiency without overheating the oil is to run a fined cover. More capacity doesn't by itself reduce oil temp (though it does dampen temp spikes and slow the rate of temp rise) but a finned, high capacity cover has more surface area for cooling. In my own case, such a cover reduced max oil temps by ~15-20F and that's one reason why I can run 90 grade and still tow 10K pounds while staying under 220F. I occasionally see some spikes higher but in the areas I go that is very seldom, of short duration and never over 240.
The best response to a question I've seen here, and I've been here since day one. Many thanks
Originally Posted By: tdi-rick
Originally Posted By: Jim Allen
BTW, another way to be able to run a thinner oil for more efficiency without overheating the oil is to run a fined cover. More capacity doesn't by itself reduce oil temp (though it does dampen temp spikes and slow the rate of temp rise) but a finned, high capacity cover has more surface area for cooling. In my own case, such a cover reduced max oil temps by ~15-20F and that's one reason why I can run 90 grade and still tow 10K pounds while staying under 220F. I occasionally see some spikes higher but in the areas I go that is very seldom, of short duration and never over 240.
I went the other way (xW-90 to 80W-140) purely as the rear diff now sports an 8mm nodular iron cover and so won't dissipate heat near as effectively as the original tin cover.
I'm not sure I really want to know how hot the diff gets now, it would take skin off my thermally calibrated finger when it was still only using a tin cover.
Remember also that the more heavily hypoid a crown wheel is the more heat generated.
A centreline spiral bevel design runs significantly cooler than something like a Dana 60 or Ford 9".
Steve, what car ?
Ford and Holden spec 80W-140 as the Dana diffs are smallish with lots of torque going through them.
They also seem prone to bearing wear too.
BA Falcon wagon with complete new rear end. Went from a M78 3.23 stocker to an M80 3.46 4-pinion LSD all brand new. Oil is VP Fuels 85W140 which is supposedly full syn and obsolete product. Very interested in diff temp guage, just need to see who sells 'em.
Originally Posted By: Jim Allen
BTW, another way to be able to run a thinner oil for more efficiency without overheating the oil is to run a fined cover. More capacity doesn't by itself reduce oil temp (though it does dampen temp spikes and slow the rate of temp rise) but a finned, high capacity cover has more surface area for cooling. In my own case, such a cover reduced max oil temps by ~15-20F and that's one reason why I can run 90 grade and still tow 10K pounds while staying under 220F. I occasionally see some spikes higher but in the areas I go that is very seldom, of short duration and never over 240.
I went the other way (xW-90 to 80W-140) purely as the rear diff now sports an 8mm nodular iron cover and so won't dissipate heat near as effectively as the original tin cover.
I'm not sure I really want to know how hot the diff gets now, it would take skin off my thermally calibrated finger when it was still only using a tin cover.
Remember also that the more heavily hypoid a crown wheel is the more heat generated.
A centreline spiral bevel design runs significantly cooler than something like a Dana 60 or Ford 9".
Steve, what car ?
Ford and Holden spec 80W-140 as the Dana diffs are smallish with lots of torque going through them.
They also seem prone to bearing wear too.
BA Falcon wagon with complete new rear end. Went from a M78 3.23 stocker to an M80 3.46 4-pinion LSD all brand new. Oil is VP Fuels 85W140 which is supposedly full syn and obsolete product. Very interested in diff temp guage, just need to see who sells 'em.
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Any oil temp gauge that goes up to 300F will work. 250F is OK too is your diff doesn't get hot. AutoMeter and Isspro both make gauges marked with "Diff Temp" or somesuch, if that's important to you. A couple of important installation tips:
1) Ground the axle to the chassis. If the springs are mounted in rubber bushings, you don't get a good ground for the sender and the gauge doesn't work or reads inaccurately.
2) There are two schools of though as to where to place the sensor. One says anywhere in the oil is OK to get bulk temps. Another says above the ring gear (in the direction of rotation) to catch the oil flowing off the ring gear (crown wheel for you I guess ( : < ) as it rotates. Eitehr is OK but having doen both, the latter reads a little higher but doesn't read anything when the diff is still.
As to interpreting temps, know what to expect is helpful:
1) Stabilized oil temp with be higher the faster you go.
2) Ring and pinions with low speed ratios (4.10, 4.56, 4.88) run hotter than high speed ratios (2.76, 3.08, etc) because there is higher gear teeth contact pressure.
3) Diff oil temp is highest on ring and pinions with a lot of hypoid offset, such as the high offset axles ... Ford 9-inch dropout (2.38" offset) and Chrysler 8.25 and 9.25 axles (1.85" offset) versus the more common 1.25-1.50" offset that most axles have. Old school spiral bevel axles run the coolest and have no offset but they are the weaker than hypoid gearsets
4) Vehicle weight and windage will have the most effect on oil temps, and that also relates to load. Climbing hills is like adding weight, so oil temp goes up.
5) Ambient temp also effect oil temps as you would expect.
Thanks for the kind words.
1) Ground the axle to the chassis. If the springs are mounted in rubber bushings, you don't get a good ground for the sender and the gauge doesn't work or reads inaccurately.
2) There are two schools of though as to where to place the sensor. One says anywhere in the oil is OK to get bulk temps. Another says above the ring gear (in the direction of rotation) to catch the oil flowing off the ring gear (crown wheel for you I guess ( : < ) as it rotates. Eitehr is OK but having doen both, the latter reads a little higher but doesn't read anything when the diff is still.
As to interpreting temps, know what to expect is helpful:
1) Stabilized oil temp with be higher the faster you go.
2) Ring and pinions with low speed ratios (4.10, 4.56, 4.88) run hotter than high speed ratios (2.76, 3.08, etc) because there is higher gear teeth contact pressure.
3) Diff oil temp is highest on ring and pinions with a lot of hypoid offset, such as the high offset axles ... Ford 9-inch dropout (2.38" offset) and Chrysler 8.25 and 9.25 axles (1.85" offset) versus the more common 1.25-1.50" offset that most axles have. Old school spiral bevel axles run the coolest and have no offset but they are the weaker than hypoid gearsets
4) Vehicle weight and windage will have the most effect on oil temps, and that also relates to load. Climbing hills is like adding weight, so oil temp goes up.
5) Ambient temp also effect oil temps as you would expect.
Thanks for the kind words.
The old Falcon LSD! We rebuilt many in my time at Ford. Ford NZ would pay under warranty for us to use Redline 80w140 in problem ones as the Castrol SAF-XA we usually used just wasn't up to the task in ones that got a hard time. I'd be hesitant to go thinner than the factory spec especially if you intend to tow a lot. XXW-140 from Motul, Redline or Amsoil would be my choice going on past experience with these vehicles.
I though in aussie thicker was better? You must be the exception to the rule
I though in aussie thicker was better? You must be the exception to the rule
Originally Posted By: SXE10
The old Falcon LSD! We rebuilt many in my time at Ford. Ford NZ would pay under warranty for us to use Redline 80w140 in problem ones as the Castrol SAF-XA we usually used just wasn't up to the task in ones that got a hard time. I'd be hesitant to go thinner than the factory spec especially if you intend to tow a lot. XXW-140 from Motul, Redline or Amsoil would be my choice going on past experience with these vehicles.
I though in aussie thicker was better? You must be the exception to the rule
Interesting re your experience with SAF-XA.
What was 'wearing' ?
Bearings or CWP's ?
The old Falcon LSD! We rebuilt many in my time at Ford. Ford NZ would pay under warranty for us to use Redline 80w140 in problem ones as the Castrol SAF-XA we usually used just wasn't up to the task in ones that got a hard time. I'd be hesitant to go thinner than the factory spec especially if you intend to tow a lot. XXW-140 from Motul, Redline or Amsoil would be my choice going on past experience with these vehicles.
I though in aussie thicker was better? You must be the exception to the rule
Interesting re your experience with SAF-XA.
What was 'wearing' ?
Bearings or CWP's ?
Originally Posted By: tdi-rick
We really need a 'thanks' or like 'button', nice reply again Jim
X2...Many THANKS for sharing , it is greatly appreciated.
)
We really need a 'thanks' or like 'button', nice reply again Jim
X2...Many THANKS for sharing , it is greatly appreciated.
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