differential fluid for towing rubicon 50 towing.

[yrwins]

Hello guys,

I need your opinion what do you guys recommend for a towing my jeep do 50% and the other city.
I have a rubicon Diesle.
75w140 synthetic
75W-90 grade

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[jac04]

75W140 for the rear diff.

 

[DiehardTory]

Exactly what the owners manual specifies.

 

[jac04]

Here's some more info:
https://www.jeepgladiatorforum.com/forum/threads/axle-fluid-weight-and-quantity….48702/#post-787840

 

[GladiatorPilot23]

The gear mesh and tolerance is different with these newer axles. You want to use 75w-85 even when towing but use the best oils Like Redline or Amsoil. Going from a stock to 75w-90 is a 30% increase in viscosity. It has been discussed on another eco tech group about tolerances being tight, thicker oil will increase wear in this case. I recall also Lake Speed Jr in his vids mentioned to stay with the OEM viscosity as well. Your MPGs will also suffer.

If you do deicide to do it anyway, do oil analysis with Polaris labs. The best labs are ISO and Blackstone gives wrong numbers since it is not ISO. It would be best to do 3 analysis using the same oil on the 75w-85. Then going thicker with the same oil and doing 3 more analysis. Look for changes in wear metals, that way you know if your helping or hurting.

 

[ShadowsPapa]

The gear mesh and tolerance is different with these newer axles. You want to use 75w-85 even when towing but use the best oils Like Redline or Amsoil. Going from a stock to 75w-90 is a 30% increase in viscosity. It has been discussed on another eco tech group about tolerances being tight, thicker oil will increase wear in this case. I recall also Lake Speed Jr in his vids mentioned to stay with the OEM viscosity as well. Your MPGs will also suffer.

If you do deicide to do it anyway, do oil analysis with Polaris labs. The best labs are ISO and Blackstone gives wrong numbers since it is not ISO. It would be best to do 3 analysis using the same oil on the 75w-85. Then going thicker with the same oil and doing 3 more analysis. Look for changes in wear metals, that way you know if your helping or hurting.

Pinion bearings are also different - gone are the tapered roller bearings. They have a dual ball bearing up there. Those can be problematic with incorrect or lesser quality fluids.
The lube is sent to the front of the differential housing for the pinion bearings by the ring gear doing a splash feed. If it's too thick, it's not going to get there as well. There's videos of that action using a clear differential cover. That fluid needs to move to the axle bearings and pinion bearings, and literally "run" or drip down into them.

I stick to the specs - including the fluid spec numbers. There's some I just will not use because of test data I've seen, so no "fancy name" lubes for my truck.

 

[jac04]

It is a good idea to follow the oil recommendations in the Owner's Manual. However, the OEM (Dana) specifies 75W-140 oil in their Dana 44 AdvanTEK rebuild specifications (see below). Is there is something different about the factory-installed D44A versus the Dana D44A that would necessitate the use of a different oil?

REAR Dana rebuild spec:
https://media.spicerparts.com/cfs/f...token=eyJhdXRoVG9rZW4iOiIifQ==&store=original

FRONT Dana rebuild spec:
https://media.spicerparts.com/cfs/f...token=eyJhdXRoVG9rZW4iOiIifQ==&store=original

 

[ShadowsPapa]

I'd prefer seeing a detailed breakdown of parts and numbers as those really show nothing about what could be different.

 

[Viper501]

RTFM.

 

[jac04]

I'd prefer seeing a detailed breakdown of parts and numbers as those really show nothing about what could be different.

I was thinking the same thing, so I looked into it a little.

The parts shown on the Dana rear Rebuild Spec Sheet (the one that calls for 75W-140), namely the Ring & Pinion Set, Standard Install Kit and Master Install Kit, are all the same as those shown when looking up the parts for a factory JT. So, it appears that they are the same.

EDIT: Thinking more about it, just because the Dana/Spicer parts shown for the 'aftermarket' and factory applications are the same doesn't 100% guarantee that the Dana/Spicer parts are what was used in the factory axles. But, I would be surprised if there was any difference necessitating the use of only 75W-85 in factory supplied axles.

Rebuild Spec Sheet:

SpicerParts.com:

 

[ShadowsPapa]

I was thinking the same thing, so I looked into it a little.

The parts shown on the Dana rear Rebuild Spec Sheet (the one that calls for 75W-140), namely the Ring & Pinion Set, Standard Install Kit and Master Install Kit, are all the same as those shown when looking up the parts for a factory JT. So, it appears that they are the same.

EDIT: Thinking more about it, just because the Dana/Spicer parts shown for the 'aftermarket' and factory applications are the same doesn't 100% guarantee that the Dana/Spicer parts are what was used in the factory axles. But, I would be surprised if there was any difference necessitating the use of only 75W-85 in factory supplied axles.

Rebuild Spec Sheet:

SpicerParts.com:

I'd be curious about the pinion bearing part numbers and so on....... there's got to be something there, aside from the usual conspiracy bits LOL

 

[GladiatorPilot23]

I was thinking the same thing, so I looked into it a little.

The parts shown on the Dana rear Rebuild Spec Sheet (the one that calls for 75W-140), namely the Ring & Pinion Set, Standard Install Kit and Master Install Kit, are all the same as those shown when looking up the parts for a factory JT. So, it appears that they are the same.

EDIT: Thinking more about it, just because the Dana/Spicer parts shown for the 'aftermarket' and factory applications are the same doesn't 100% guarantee that the Dana/Spicer parts are what was used in the factory axles. But, I would be surprised if there was any difference necessitating the use of only 75W-85 in factory supplied axles.

Rebuild Spec Sheet:

SpicerParts.com:

Hmmm tough to verify.

Here it shows both??? In the owners manual one 75w-85??

Keep in mind this is a "Jeep Performance Part" may be different the factory one.

https://www.allmoparparts.com/docs/...tBaEDurXZ5TACPIa6SDB3mxZ_ZN_IJugcJ13Zl21xQHwa




For sure MPG will go down with 85w-140 but will wear go down? Only testing the oil 3 times each would show.

 

[Vtur]

I'd be curious about the pinion bearing part numbers and so on....... there's got to be something there, aside from the usual conspiracy bits LOL

My Dana's master kit came with Timken head bearing and Koyo tail bearing. Both matched with factory bearings.

 

[Maximus Gladius]

Hmmm tough to verify.

Here it shows both??? In the owners manual one 75w-85??

Keep in mind this is a "Jeep Performance Part" may be different the factory one.

https://www.allmoparparts.com/docs/...tBaEDurXZ5TACPIa6SDB3mxZ_ZN_IJugcJ13Zl21xQHwa




For sure MPG will go down with 85w-140 but will wear go down? Only testing the oil 3 times each would show.

Though I agree completely with doing oil analyses on all your components to see how wear metals are trending, and you’re suggesting 3 tests to know if the oil picked was a good decision, how many miles are you suggesting between tests x’ 3 ?

 

[jac04]

One other thing I looked at when I decided to go with 75W140 in my JTM rear diff was the viscosity versus temperature chart per ASTM D341. Over on the JL forums, there was data posted by CarbonSteel on rear diff operating temperatures, showing fairly high operating temperatures: https://www.jlwranglerforums.com/forum/threads/diff-fluid-wrangler-jl.97387/

Looking at Valvoline Synpower 75W90 versus 75W140 at 100C (212F):
75W140 provides the same viscosity at 262F as 75W90 at 212F
75W140 provides the same viscosity at 212F as 75W90 at 172F
So, using 75W140 is like decreasing the diff temp when using 75W90 by 40-50F at the 'high end' operating temperature. IMO, the increase in viscosity at operating temperature is only a good thing.

But, low temperature viscosity also needs to be considered. Since I live in CT, I focused on -20C (-4F) as my low temperature point.
75W140 provides the same viscosity at 14F as 75W90 at -4F
75W140 provides the same viscosity at -4F as 75W90 at -18F
So, using 75W140 is like decreasing the diff temp when using 75W90 by 14-18F at 'cold start'.
Excessive viscosity is not necessarily a good thing at cold start. But, IMO (for my use case), the increase in viscosity from using 75W140 falls within the viscosity range for 75W90 at design low-end temperatures.

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