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Rear Dana 44 (JLU) Aftermarket Covers and Heat load!

oldcjguy

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On top of that ratio's over 373 make the situation even worse as lower ratio's (ie: .411 or lower) make the ring gear rotate many more times then a higher ratio causing the lubrication to heat up even more.

For extended expressway driving the factory steel cover or an aluminum cover is far superior over a cast iron cover to dissipate heat, this is a direct quote from Dana.
The ring gear rotates the same no matter what the ratio is. Once per axle/tire rotation. The ring gear spends the same amount of time in the oil bath. The pinion is the one that rotates more as the ratio gets numerically higher.
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grimmjeeper

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The ring gear rotates the same no matter what the ratio is. Once per axle/tire rotation. The ring gear spends the same amount of time in the oil bath. The pinion is the one that rotates more as the ratio gets numerically higher.
This.

The ring gear rotation is tied directly to tire diameter. Bigger tires rotate slower so ring gear rotates slower. The shorter (higher number) gears have a smaller pinion head with fewer teeth so those rotate faster. But with bigger tires the slower ring offsets the faster pinion, partially canceling each other out.
 

DHW

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I don't think anyone has measured (yet), but anyone care to venture a guess as to how much hotter an iron covered diff runs compared to the OEM steel cover? Are we talking 10 degrees, 50 degrees? Just curious.
 
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bd100

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Had an axle fail months after a cross-country trip towing a popup. Failed gradually, not suddenly. Stock diff cover.

One early warning sign to listen for, at least on the JT pickup, is a quiet hissing sound being transmitted from the diff to the parking brake along its cable. It sounds like a hissing at the parking brake handle which changes as you slightly move the handle up or down. Not present when new, the hissing became noticeable around 10K miles or so. The usual grumbling noises from the diff came much later, 15K miles or more. With the new diff the hissing is gone. I have now changed to 75w140 in the diff.
 
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RoadNomad

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The ratio of the differential is proportional, that is why when you go to a lower ratio from a high one (ie 342 to say 411) the engine rpm will be much higher to achieve the same speed. While it is true the ring gear is tied rotation wise to the tire the amount of teeth on the ring and pinion is different and rotates at a much higher RPM then the Higher ratio.

This helps to heat up the diff fluid much quick and help to wip it and introduce air into the oil and reduces its ability to lubricate and cool.

It is true that larger tires such as 35's help and their larger diameter will allow to offset a lower ratio, this is one of the reasons your speedo is off when you swap tire sizes. The larger tires will help but not everyone want to go out and buy bigger tires.
 

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grimmjeeper

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the difs already have drain plugs. is there some reason you would want more in the covers?
(rear, drivers side.)
Jeep Wrangler JL Rear Dana 44 (JLU) Aftermarket Covers and Heat load! IMG_3741.JPG
Newer versions of the axles did away with the drain plugs in the housing.
 

zouch

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that would be poopy.

gotta' wonder what the reason for that could be,.. how much could it possibly save them?
or are they preferring that we pull the cover every time we change fluid?


Newer versions of the axles did away with the drain plugs in the housing.
 
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Dana originally came up with an aluminum cover to help dissipate heat at the request of Nissan who started using the D44 in their trucks and experiencing heat problems and burning up bearings.

This cover was specifically designed by Dana to help channel fluid to provide the best lubrication. It featured excessively raised fins on the rear of the cover helped to pull the heat out of the fluid and bleed it off. The cover also increased the oil capacity inside the diff.

While this cover provided little protection unlike the newer iron cast covers it was far superior in removing heat from the diffs and much better then the factory steel covers.

Unfortunately it will not fit the JL series of D44's and the aftermarket aluminum covers do not have the excessively raised fins. The covers today the fins are more for looks than anything else.

Jeep Wrangler JL Rear Dana 44 (JLU) Aftermarket Covers and Heat load! cover
 

CarbonSteel

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Nice job on the temp sensor CS and its good your keeping tabs on your temperatures.

Many don't believe there is any reason to worry about high diff temps, and for the most case for general driving and off-roading temperatures remain within acceptable norms using quality lubricants.

That all goes out the window when towing and long periods of high speed vehicle operation on major expressways. I have been monitoring and experimenting with this, It is not un-common to have temperatures north of 220 degrees in the summer after driving three to four hundred miles or so. This is even worse if towing.

Right now I am working on doing some modifications on a rough country diff skid plate and making it where it will channel cool air while driving under the bottom of the diff then force it over the back of the rear cover to bleed heat. Much like a hood scoop. It will also serve to protect the diff from off road damage (even though I doubt that would ever be needed)

Good quality diff lube can only go so far to protect the D44's internal parts and heavy cast covers used to protect from impact damage will only make the situation worse as they do not allow the built up heat to dissipate.

I have spoken with a number of engineers at Dana and was told cast iron covers are good for weekend off roaders who might experience damage due to impact. But they don't recommend them for vehicles that are primarly road vehicles that are routinely used for extended high speed driving on expressways which is my application.

On top of that ratio's over 373 make the situation even worse as lower ratio's (ie: .411 or lower) make the ring gear rotate many more times then a higher ratio causing the lubrication to heat up even more.

For extended expressway driving the factory steel cover or an aluminum cover is far superior over a cast iron cover to dissipate heat, this is a direct quote from Dana.
In my experience, higher gear ratios (lower numerically) run cooler than lower gear ratios do--but it can all depend and larger tires "offset" the deeper gearing (which is why it is needed in the first place). I ran a steel cover on the Wrangler because I needed to weld in the bung for the temperature probe, but I am running a cast iron unit on my Bronco D44 (and plan to drill and tap it to install a temp probe).

Part of the Wrangler's issue is the reduction of gear oil capacity. Ford left well enough alone and I have a bit over 2 QTs in its D44 versus 1.6 QTs in the Wrangler D44.

In the end, the axles under both the Bronco and the Wrangler are smaller than the rear axle under a 1980s Mustang. They work "ok" on a 1000% stock Wrangler, but add larger tires, lower gearing, extra weight, and towing and they will, in short order, show their "true colors".

Jeep Wrangler JL Rear Dana 44 (JLU) Aftermarket Covers and Heat load! 20240101_142630
 

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I have spoken with a number of engineers at Dana and was told cast iron covers are good for weekend off roaders who might experience damage due to impact.

On top of that ratio's over 373 make the situation even worse as lower ratio's (ie: .411 or lower) make the ring gear rotate many more times then a higher ratio causing the lubrication to heat up even more.
Well I don’t know what kind of engineer you talked to but first of all we don’t put mdiff covers on for impact damage. The primary job of the HD diff cover is to strengthen the diff housings to prevent housing flex and gear deflection. If cast is no good why does Dana/Spicer offer them and include them on all the UD44 axles.

If an engineer told you the higher gear ratio ring gear rotates faster then stock, he is clueless. As already mentioned the higher gear ratio ring gear doesn’t rotate any faster, only the pinion does.
 

Jtphoto

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Part of the Wrangler's issue is the reduction of gear oil capacity. Ford left well enough alone and I have a bit over 2 QTs in its D44 versus 1.6 QTs in the Wrangler D44.

In the end, the axles under both the Bronco and the Wrangler are smaller than the rear axle under a 1980s Mustang. They work "ok" on a 1000% stock Wrangler, but add larger tires, lower gearing, extra weight, and towing and they will, in short order, show their "true colors".

Jeep Wrangler JL Rear Dana 44 (JLU) Aftermarket Covers and Heat load! 20240101_142630
The D44 axles under the JK are also bigger than the JL and Bronco AdvanTek axles. With the Dana/Spicer cast covers on the M220 it will take 2 quarts of oil.
 

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The D44 axles under the JK are also bigger than the JL and Bronco AdvanTek axles. With the Dana/Spicer cast covers on the M220 it will take 2 quarts of oil.
The cavity in the DS cover is no deeper or larger than the OEM stamped steel cover. I am sure that it may be possible to fill the axle to 2 QTs, but I had asked DS at one point if the cast cover increases the capacity and was told no, it did not.

OEM:

Jeep Wrangler JL Rear Dana 44 (JLU) Aftermarket Covers and Heat load! OEM Cover


Dana Spicer:

Jeep Wrangler JL Rear Dana 44 (JLU) Aftermarket Covers and Heat load! Spicer Cover
 

Jtphoto

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The cavity in the DS cover is no deeper or larger than the OEM stamped steel cover. I am sure that it may be possible to fill the axle to 2 QTs, but I had asked DS at one point if the cast cover increases the capacity and was told no, it did not.

OEM:

Jeep Wrangler JL Rear Dana 44 (JLU) Aftermarket Covers and Heat load! Spicer Cover


Dana Spicer:

Jeep Wrangler JL Rear Dana 44 (JLU) Aftermarket Covers and Heat load! Spicer Cover
I have the Dana/Spicer covers on my JL. They are a bit deeper then the steel cover and correct, the bottom fill hole is the same height as the factory cover.
 

grimmjeeper

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Well I don’t know what kind of engineer you talked to but first of all we don’t put mdiff covers on for impact damage. The primary job of the HD diff cover is to strengthen the diff housings to prevent housing flex and gear deflection. If cast is no good why does Dana/Spicer offer them and include them on all the UD44 axles.

If an engineer told you the higher gear ratio ring gear rotates faster then stock, he is clueless. As already mentioned the higher gear ratio ring gear doesn’t rotate any faster, only the pinion does.
You can take it a step further. When you match shorter (higher number) gears with bigger tires, the pinion actually ends up spinning around the same speed and the ring gear is turning slower than stock gears and stock tires.
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