Gear oil temp ?

[TwinStick]

I will ask the age old question, How hot is too hot ?

Vehicle: 2008 Dodge Power Wagon. 10.5" AAM 14 bolt rear & AAM 14 bolt 9.25 front. Both with electric lockers inside.

The reason I ask the age old question of how hot is too hot: I have recorded temps all over the board with my trucks. I use a laser infrared thermometer. I have tried to verify it with other infrared thermometers. They all read the same, so I am assuming it is somewhat accurate. Vehicles I have used it on: 2000 dodge dakota auto, w/360 & 3.92's towing a 3000lb tent trailer, 2004 dodge Ram 2500 w/Hemi, auto w/4.10's towing a 10,500lb toyhauler, 2008 Dodge Power Wagon w/G-56 manual, 4.56's towing a 10,500lb toyhauler & now a 3500lb 18' single axle camper.

I have bought all these vehicles new. Some temps I have recorded while towing: 195*, 285*, 315* & just recently towing the 3500lb camper w/Power Wagon 256*. I have used all kinds of different oil: Mobil1 full synthetic, Mopar full synthetic (currently in Power Wagon when recording 256*), Royal Purple full synthetic, Amsoil full synthetic & others. I will not say which oils recorded which temps because I don't want to get into a brand loyalty issue here. But needless to say, I am not very happy with any of them. None seem to last more than 11-12,000 miles in the Dodge trucks I have had. My current truck (08' Dodge Power Wagon) has recorded a temp once of 315*F. I changed the oil as soon as i got home after that trip, but what the gives here ? Are these temps normal ? I do not think that they are. I am thinking the 315* temp is what did in the rear locker actuator inside the axle. It was covered under the lifetime power train warranty but i would like to avoid this again. I have changed the diff fluid 4 times in 43,000 miles on my Power Wagon.

I ordered a Mag-Hytec rear diff cover today & will install that myself, but even if it does reduce the temp by 25-50* as claimed, I am still running too hot I think.

All trucks were brand new when I got them. Yes, fluid was up to specs. No, there were no leaks. When I read people saying their rear diff temps are 100*-130* when towing, it makes me scratch my head. I have recorded 195* when empty, using top of the line oils of the proper weight. I have even tried thicker weight gear oil. No difference.

Input please, not sarcasim.

 

[proper4wd]

256 is hot. 315 is really hot. What are the ambient temps and how fast are you going? How has the oil looked upon draining? What part of the diff are you checking with the IR?

Everything I have rear indicates that 200* is about the upper limit of normal operating range while towing.

 

[TwinStick]

I am holding the temp reader 8-10" from the rear diff cover. Laser is hitting it where the ring gear is, about 2-3" from the bottom of diff.

Ambient temp was 85-95*F. Running from 65-80 mph. 4.56 Gears in pumpkins. I have never had an axle failure but just think the temps are too high. Oil looks & smells like gear oil does. No burnt smell that i could notice, just gear oil smell.

I have read that every 20*F increase in temp above 175*F, reduces the oils life by 50%. If that is true then even 256* pretty much means the oil is toast & 315*F means it is done right then & there as well.

 

[rayra]

How much braking and how soon after was the temp checked, when you got that higher reading?

I think you are over analyzing things and locked on one aspect. And absent any failures, doing it for little reason. And the people that say 100-120 are flat lying.

Lastly, you should be putting the dot on several places on the casing when you do this and considering an average. Since the temp can vary greatly due to the structures of the casement. If your spot checks are not totally consistent then your data is essentially garbage.

And believe your nose more than your readings. If the gear oil doesnt smell burnt it isn't burnt. If it worries you so greatly, change it once a year and quit screwing with it.

Lastly, what's your ring gear look like? Maybe it was set up poorly, the lash is wrong and that may be the source of your (perceived) higher temps. Too, are you getting any excess metal in the oil? Put a small rare earth magnet on the drain plug and find out.


eta, ok nevermind, saw your other post about putting a cage in a van. You're a worrywart, I ain't got time to cater to that kind of dysfunction.

 

[TwinStick]

Just got back from a 12 mile trip to town & back, empty, 55mph. 133*F is what it read anywhere on the bottom of pumpkin cover. :Wow1: Just trying to figure out what the deal is. Those temps were not after a lot of braking either. Highway speed, slow down 2 stops then checked. After dinner about 45 min - 1 hr, it was still reading 205*f from the 256*f reading.

 

[TwinStick]

How much braking and how soon after was the temp checked, when you got that higher reading?

Highway speed, slow down w/no brake, get off exit, 1 stop sign. Then to gas station 1 stop. Checked. Flat ground no downhill braking before.

I think you are over analyzing things and locked on one aspect. And absent any failures, doing it for little reason. And the people that say 100-120 are flat lying.

Yeah, cause I just love doing things for no reason !

Lastly, you should be putting the dot on several places on the casing when you do this and considering an average. Since the temp can vary greatly due to the structures of the casement. If your spot checks are not totally consistent then your data is essentially garbage.

Wow, good thing you told me that, I never would have known that !!!

And believe your nose more than your readings. If the gear oil doesnt smell burnt it isn't burnt. If it worries you so greatly, change it once a year and quit screwing with it.

Lastly, what's your ring gear look like? Maybe it was set up poorly, the lash is wrong and that may be the source of your (perceived) higher temps. Too, are you getting any excess metal in the oil? Put a small rare earth magnet on the drain plug and find out.

In all 3 trucks ? Set up wrong ? I think not. Not only is there the factory magnet, there is also a GP101 from filter-mag in there. Yeah, there is a stuff on them every time, Not a lot but it is certainly there. The consistency of never-seize.


eta, ok nevermind, saw your other post about putting a cage in a van. You're a worrywart, I ain't got time to cater to that kind of dysfunction.

Finally, i asked in my first post, input please, not sarcasm.

 

[TwinStick]

https://www.youtube.com/watch?v=OCevnkptGcQ

 

[Stumpalump]

Two oils are great. Red line heavy shock proof and the high end Mercruiser drive lube. I run the Redline in an 091 transaxle with a Proam shifter. It's got all Weddle gears and bigger bearings. It shifts like a rice rocket and temps stay cooler than my buddies that run better Mendeola transmissions. We beat gear lube hard. http://www.pmdraceproducts.com/itemdetailspage/22805

http://www.mertenmarine.com/Mercury-Racing-Gear-Lube--1-Quart_p_6347.html You can get this in 5 gallon buckets. Might be better than Redline if you want best gas milage, run jap stuff or see frozen places. My buddy owns a lube service for heavy equipment like cranes. He uses the Mercury stuff in his race Mendeola and swares by it. He does not break. Race outdrives kill regular gear lube.

I like this. http://www.redlineoil.com/product.aspx?pid=44&pcid=8 The way I drive and how well my stuff lasts has convinced a few of my buddies to swap over to it. Too thick for jap stuff. Only lube you can feel that it's better.

If you beat your equipment you need the best stuff. Try that Redline. Any local speed shop should have it.
Nothing is harder on lube than a transaxle. Make sure you squeeze in extra in your pumpkin. If you notice, aftermarket covers have the fill level higher than stock. Nothing wrong with a quart of Lucas oil stabilizer if you don't want to spring for the race stuff. The non synthetic is best because it does not run off gears as fast. Some have seen front bearings or pinion bearings fail on long climbs with synthetic. The regular lube sticks in the bearings better than synthetic.

 

[(none)]

IR guns are not very accurate form of measurement for something like that. A shiny black diff cover can get you some false readings, including reflections such as off of the exhaust.

The most accurate measurements would be a thermocouple in the drain plug. 2nd best would be to stop, open the fill plug and insert a thermocouple into the oil connected to a multimeter or even a meat thermometer will work.

300+ F is way over what your engine oil temp is running, so i seriously doubt your diffs are running that hot.

 

[Deleted member 9101]

Sounds like a "false positive." Class 8 trucks don't even run those temps and they are at 80, 000 pounds and exerting expentionailly more stress on their diffs.

 

[BigSwede]

IR guns are not very accurate form of measurement for something like that. A shiny black diff cover can get you some false readings, including reflections such as off of the exhaust.

I was just gonna say...

 

[TwinStick]

It was aimed at different points on the rear diff cover, not even facing the exhaust. I will look into this further & try something different. I can tell you that touching it is something I would not do. You can just feel the radiating off it when close to it. Maybe I will try a digital meat thermometer, one that goes over 200* & put it in the fill hole, so it is actually in the fluid. I will get back to this in a day or 2. Stand by please.

 

[Stumpalump]

A nurse feels a patient with the back of her hand. A boat owner can touch any part of a marine engine and none of it should burn. On a radiator you should be able to touch it a 2 seconds. If it burns right away you are over 230. Just count the seconds you can touch it before you yank away. If you can't even touch it then you are about to boil the antifreeze. On a diff cover, put your whole hand on the cover. You should be able to leave it on the cover for at least 3 seconds. Less than that and you are getting warm. If you have a misfiring engine then you can let it cool first then start it. The firing cylinders will get to hot to touch in seconds but the cylinder missing will be obviously cooler when touching the exhaust. Seriously if you can't feel an engine that is 160, 180, 200 220 and 240 then go practice and count the seconds you can touch it. Mandatory skill if you buy gasoline. If somthing is way to hot to touch then use spit and look to see how fast it vaporizes. If you spit on a car intake or valve cover it should not turn to steam. If you use your breaks a lot a diff should run cool but if you coast to stops or downshift they run hotter. Hotshots that pull with 1 ton trucks wear out the coast side of the ring faster than the driven because they use engine breaking on grades. That's how much harder coasting is than driving on a diff. That's also a good way to determine if you should change the lube more often.

 

[NatersXJ6]

I'll throw down a stupid question or two:

Are you sure it is full? Typically a bearing that is running in an oil bath needs to be full to 1/3 of the depth of the roller, give or take. Being empty means not enough lube = heat.

Are you sure it isn't overfilled? Too much oil means too much resistance = heat. In this case, I think some would leak out the breather.

What weight oil are you running? Have you plotted viscosity curves for that oil? Many oils can survive higher temps without loss of viscosity.

It has been over 15 years since I worked with gear drive designs, but we used to figure that we had issues around 150 over ambient temp. IIRC.

Are you getting abnormally low mileage? If something is overheating your oil, it has to be dragging on your system to the point of noticeable.

Have you lifted the rear end and spun the wheels by hand to see if everything moves freely?

 

[javajoe79]

If you are that concerned, hook up a gauge and watch what it does while driving. If it's actually getting too hot for your liking, add a pump and cooler or a finned cover or fab a cover with more capacity.