In the next few wekks I'm due to change the gear oil in my rear differential, Ford specs 80W90 for the 8.8", I plan to tow my sailboat this summer with her, should I step up to 85W140 or stick with the 80W90?
Changing Rear Differential Gear Oil
- Thread starter Maritime Storm
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How heavy a trailer and how far and how fast? - its all temp AFA towing goes. Dont use the heavy stuff unless you really need it.
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Buy two quarts of 80W90 and another same brand 85W140.
Assuming you aren't grossly overloading the truck, the 80w90 will be fine in your climate.
Either 80W90 or 75W140 will work fine. Since you plan on towing, a synthetic 75W140 would be the way to go IMO.
80/90 would be my choice. Your owner manual may suggest different fot towing but, I doubt it.
I'd use the factory recommended 80-90, but I'd get a full synthetic version.
Remember, you also will see tough winters ahead!
We don't change diff oil often, so get the best that you can.
Remember, you also will see tough winters ahead!
We don't change diff oil often, so get the best that you can.
I've never owned a truck, but I would think the stated use would be a good place to use the "new" 75W110 created when 75w90 was split. Something like Amsoil SVT?
I could be mistaken, but I don't see a 75W rating being inferior to an 80W rating on the cold side. I thought that prior to the 90 "split", 80W90 was used to indicate a heavier 90, which would put "new" 75W110 right on the money.
Again, I could be wrong.
I could be mistaken, but I don't see a 75W rating being inferior to an 80W rating on the cold side. I thought that prior to the 90 "split", 80W90 was used to indicate a heavier 90, which would put "new" 75W110 right on the money.
Again, I could be wrong.
MolaKule
Staff member
I agree with Craig.
Use one of the new 75W110's; a good all weather, max protection lube.
Use one of the new 75W110's; a good all weather, max protection lube.
I agree, if he wants to spend the money on a synth. I went with a 75W110 in my 8.8 because I tend to be hard on it. Recommendation for a civilian CV is 80W90 as well.
Originally Posted By: 01rangerxl
Either 80W90 or 75W140 will work fine. Since you plan on towing, a synthetic 75W140 would be the way to go IMO.
I agree with this. Ford now recommends 75W140 in all 8.8 rear differentials.
What vehicle is it and what axel ratio? Trac-Loc or conventional?
Either 80W90 or 75W140 will work fine. Since you plan on towing, a synthetic 75W140 would be the way to go IMO.
I agree with this. Ford now recommends 75W140 in all 8.8 rear differentials.
What vehicle is it and what axel ratio? Trac-Loc or conventional?
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The boat weighs in around 4500Lbs on it's trailer. The truck is rated for 6000Lbs. 2009 Ranger Sport 8.8" 3.55:1 open rear. When did Ford start recommending 75W140? My Owners Manual states 80W90, if it's sufficient for the job I'll stick with it. It will be changed every 2years after this.
Originally Posted By: Maritime Storm
The boat weighs in around 4500Lbs on it's trailer. The truck is rated for 6000Lbs. 2009 Ranger Sport 8.8" 3.55:1 open rear. When did Ford start recommending 75W140? My Owners Manual states 80W90, if it's sufficient for the job I'll stick with it. It will be changed every 2years after this.
Ignore the manual, call you local parts man.
This is actually a grey area. Ford chose the 75W140 to cover their behind. You can go with the lighter oil if you want.
The boat weighs in around 4500Lbs on it's trailer. The truck is rated for 6000Lbs. 2009 Ranger Sport 8.8" 3.55:1 open rear. When did Ford start recommending 75W140? My Owners Manual states 80W90, if it's sufficient for the job I'll stick with it. It will be changed every 2years after this.
Ignore the manual, call you local parts man.
This is actually a grey area. Ford chose the 75W140 to cover their behind. You can go with the lighter oil if you want.
Any advantage to going to 75W140? The tests here on the site seemed to indicate that synthetics didn't climb the gears as well in cold temps. Is it a myth?
75W140 will give you some protection in high heat high load conditions. It will also cost you 1% in fuel economy, and the axel will run a bit hotter. A 4500lb load is nothing to sneeze at, and if it were me I would be running the 75W140 in that setup. Ford dealer will say the same.
Explorers have 75W140 as FF with 3:73 ot 4:10 gear ratios or with Trac-Lok diff. I am useing redline 75W140 in my Explorer with 4:10 gears, and I only do light towing.
I don't know if the synthetics climb the gears well or not, but they seem to be FF in any heavy-duty application.
Explorers have 75W140 as FF with 3:73 ot 4:10 gear ratios or with Trac-Lok diff. I am useing redline 75W140 in my Explorer with 4:10 gears, and I only do light towing.
I don't know if the synthetics climb the gears well or not, but they seem to be FF in any heavy-duty application.
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Thank you
Originally Posted By: Bluestream
75W140 will give you some protection in high heat high load conditions. It will also cost you 1% in fuel economy, and the axel will run a bit hotter. A 4500lb load is nothing to sneeze at, and if it were me I would be running the 75W140 in that setup. Ford dealer will say the same.
Explorers have 75W140 as FF with 3:73 ot 4:10 gear ratios or with Trac-Lok diff. I am useing redline 75W140 in my Explorer with 4:10 gears, and I only do light towing.
I don't know if the synthetics climb the gears well or not, but they seem to be FF in any heavy-duty application.
Bluestream is right about the 140 costing fuel economy and running hotter. I had to switch from a syn 75W140 to a "nuthin'-special" mineral 80W90 because the new limited slip I got requires it. My diff temp went DOWN 10 degrees, despite new bearings on the carrier, slightly tighter setup, and a much warmer day on the return trip.
As to fuel economy, I can't definitively say much... if it were 1%, that would be hard to pull out of the normal variable "noise" that occurs with "normal" methods of MPG testing. Seems like there's been a slight uptick on mine and it could be more significant looked at cumulatively over a long period.
After a fair bit of fooling around, I have come to the conclusion that my diff oil viscosity choices should base on oil temperature. Therefore, job-one for is to install a diff temp gauge and monitor it under all operating conditions. Since I run a small farm, that includes hauling and towing. There are diff temp gauges on both my working trucks.... both Fords and both 10.25 axles. Both now have Mag-Hytec covers, which have a bung for a temp sender, however I welded in a bung onto the original steel cover of the older truck before the Mag-Hytec was installed. AutoMeter sells those bungs for a coupla bucks each and you can use any kind of temp gauge, though I know both AutoMeter and Isspro make some marked "Diff Temp." A tip: On a one wire gauge, run a ground wire from the axle to the chassis because there is not always a great ground through the springs or driveshaft.
My own criteria for the viscosity choice is whether or not the diff oil temp exceeds the 212F (100C) degree threshold significantly or long term. AYK, 212F is the point at which the hot viscosity measurement is taken. Using a temp vs viscosity chart (good ol' Widman has one on his site), I want to keep the oil at no less than about the bottom of the 90 grade range, around 14 cSt at whatever my highest sustained temp is. I don't worry about an occasional short spike unless it's well over 250F. Most oils can handle that for a few minutes. If an axle runs at a sustained 250F towing, however, a 90 grade could be down in the 75-80 grade area. That's not immediately harmful either but long term it could be, so that would dictate a 110 or 140 grade to maintain that minimum viscosity.
You have to monitor your oil temps for a while to rack up the data. I have compared mine with other guys as pedantic as me and I am surprised at both how high and how low diff temps run on various trucks. I have learned that the Mag-Hytec cover knocks an average of about 15 degrees off diff oil temp. I also learned that a good syn oil can knock an honest 10F off the same viscosity grade of mineral oil. Knowing both of these things has shown me that my truck can safely run a 90 grade for whatever increase there is in fuel economy day to day with no worries about dropping out of the 90 grade.
My overall logic is that if you tow 5 percent of the time, it makes no sense to hurt yourself MPG-wise by running a heavier grade oil than you need.... even if that hurt is only 1%. If you live in a cold climate that hit could be more in the winter. If the oil temp exceed 212F towing for five minutes going up a hill, no biggie. It will cool back down. It's possible that you might see some overly high temps towing only occasionally, so you might have to take the hit in the daily driving department and use a heavier oil to preserve the axle. I contend, however, that a diff temp gauge allows you to monitor and make adjustments to the situation to keep that temp lower (see the list below). Also, a higher capacity, finned cover might be enough to maintain those lower maximum temps, though it also keeps the oil cooler longer.
Assuming demonstrated overly high temps, I've crunched the numbers a couple of ways and using 1% drop of economy, it comes out somewhat cheaper to just use the heavier oil than to spend a lot of money on covers and such, but that would depend on how much hit there truly is on fuel economy and the cost of fuel. I strongly believe the diff temp gauge is a worthwhile addition for any truck that tows.
Some general things I have learned:
1) At a given load, a larger ring gear axle will run cooler than a smaller (more tooth contact to spread the load)
2) At a given load, a lower ratio (4.10. 4.56:1 etc) will run hotter than a lower (3.23-3.55:1, etc, ... more hypoid action creating more heat)
3) At the same viscosity a syn oil will run about 10 F cooler than a mineral, EXCEPT mineral oils with special additives. I used a LE oil (LE607), which was a straight 90 but one that had lots of a proprietary moly-like additive that surprised my by running as cool as a well-known syn. The Chevron ESI oils are said to exhibit similar characteristics, though I have not seen that demonstrated personally.
4) Fluid friction from an oil heavier than needed causes the oil to run hotter.
5) At any given load, the faster you go, the hotter the diff runs. SOme of that is load due to windage but some comes from the diff itself... that hypoind sliding action occurring more often and heating theoil faster.
6) A higher viscosity oil than you need for the temp range costs fuel economy.
75W140 will give you some protection in high heat high load conditions. It will also cost you 1% in fuel economy, and the axel will run a bit hotter. A 4500lb load is nothing to sneeze at, and if it were me I would be running the 75W140 in that setup. Ford dealer will say the same.
Explorers have 75W140 as FF with 3:73 ot 4:10 gear ratios or with Trac-Lok diff. I am useing redline 75W140 in my Explorer with 4:10 gears, and I only do light towing.
I don't know if the synthetics climb the gears well or not, but they seem to be FF in any heavy-duty application.
Bluestream is right about the 140 costing fuel economy and running hotter. I had to switch from a syn 75W140 to a "nuthin'-special" mineral 80W90 because the new limited slip I got requires it. My diff temp went DOWN 10 degrees, despite new bearings on the carrier, slightly tighter setup, and a much warmer day on the return trip.
As to fuel economy, I can't definitively say much... if it were 1%, that would be hard to pull out of the normal variable "noise" that occurs with "normal" methods of MPG testing. Seems like there's been a slight uptick on mine and it could be more significant looked at cumulatively over a long period.
After a fair bit of fooling around, I have come to the conclusion that my diff oil viscosity choices should base on oil temperature. Therefore, job-one for is to install a diff temp gauge and monitor it under all operating conditions. Since I run a small farm, that includes hauling and towing. There are diff temp gauges on both my working trucks.... both Fords and both 10.25 axles. Both now have Mag-Hytec covers, which have a bung for a temp sender, however I welded in a bung onto the original steel cover of the older truck before the Mag-Hytec was installed. AutoMeter sells those bungs for a coupla bucks each and you can use any kind of temp gauge, though I know both AutoMeter and Isspro make some marked "Diff Temp." A tip: On a one wire gauge, run a ground wire from the axle to the chassis because there is not always a great ground through the springs or driveshaft.
My own criteria for the viscosity choice is whether or not the diff oil temp exceeds the 212F (100C) degree threshold significantly or long term. AYK, 212F is the point at which the hot viscosity measurement is taken. Using a temp vs viscosity chart (good ol' Widman has one on his site), I want to keep the oil at no less than about the bottom of the 90 grade range, around 14 cSt at whatever my highest sustained temp is. I don't worry about an occasional short spike unless it's well over 250F. Most oils can handle that for a few minutes. If an axle runs at a sustained 250F towing, however, a 90 grade could be down in the 75-80 grade area. That's not immediately harmful either but long term it could be, so that would dictate a 110 or 140 grade to maintain that minimum viscosity.
You have to monitor your oil temps for a while to rack up the data. I have compared mine with other guys as pedantic as me and I am surprised at both how high and how low diff temps run on various trucks. I have learned that the Mag-Hytec cover knocks an average of about 15 degrees off diff oil temp. I also learned that a good syn oil can knock an honest 10F off the same viscosity grade of mineral oil. Knowing both of these things has shown me that my truck can safely run a 90 grade for whatever increase there is in fuel economy day to day with no worries about dropping out of the 90 grade.
My overall logic is that if you tow 5 percent of the time, it makes no sense to hurt yourself MPG-wise by running a heavier grade oil than you need.... even if that hurt is only 1%. If you live in a cold climate that hit could be more in the winter. If the oil temp exceed 212F towing for five minutes going up a hill, no biggie. It will cool back down. It's possible that you might see some overly high temps towing only occasionally, so you might have to take the hit in the daily driving department and use a heavier oil to preserve the axle. I contend, however, that a diff temp gauge allows you to monitor and make adjustments to the situation to keep that temp lower (see the list below). Also, a higher capacity, finned cover might be enough to maintain those lower maximum temps, though it also keeps the oil cooler longer.
Assuming demonstrated overly high temps, I've crunched the numbers a couple of ways and using 1% drop of economy, it comes out somewhat cheaper to just use the heavier oil than to spend a lot of money on covers and such, but that would depend on how much hit there truly is on fuel economy and the cost of fuel. I strongly believe the diff temp gauge is a worthwhile addition for any truck that tows.
Some general things I have learned:
1) At a given load, a larger ring gear axle will run cooler than a smaller (more tooth contact to spread the load)
2) At a given load, a lower ratio (4.10. 4.56:1 etc) will run hotter than a lower (3.23-3.55:1, etc, ... more hypoid action creating more heat)
3) At the same viscosity a syn oil will run about 10 F cooler than a mineral, EXCEPT mineral oils with special additives. I used a LE oil (LE607), which was a straight 90 but one that had lots of a proprietary moly-like additive that surprised my by running as cool as a well-known syn. The Chevron ESI oils are said to exhibit similar characteristics, though I have not seen that demonstrated personally.
4) Fluid friction from an oil heavier than needed causes the oil to run hotter.
5) At any given load, the faster you go, the hotter the diff runs. SOme of that is load due to windage but some comes from the diff itself... that hypoind sliding action occurring more often and heating theoil faster.
6) A higher viscosity oil than you need for the temp range costs fuel economy.
Originally Posted By: Bluestream
Ford now recommends 75W140 in all 8.8 rear differentials.
I can see this in an open diff (like he has in his 8.8).
But do they really spec a synthetic in their Trac Locs (or ANY other clutch plate/friction type limited slips)??
(Like Jim A, I am required to use a mineral based gear oil in my Eaton Posi).
Ford now recommends 75W140 in all 8.8 rear differentials.
I can see this in an open diff (like he has in his 8.8).
But do they really spec a synthetic in their Trac Locs (or ANY other clutch plate/friction type limited slips)??
(Like Jim A, I am required to use a mineral based gear oil in my Eaton Posi).
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