Diff fluid - Wrangler JL

[dmen]

Hi guys, I have a 21 Willys UL with 20K on it and just changed the diff fluid in front and back. I just did it in the driveway which is pretty flat but does the amounts seem right - front took most of 1 qt and the rear took a little under 2. Also did the transfer case which took almost 2 qt... Seem right?

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[Remorseless]

Hi guys, I have a 21 Willys UL with 20K on it and just changed the diff fluid in front and back. I just did it in the driveway which is pretty flat but does the amounts seem right - front took most of 1 qt and the rear took a little under 2. Also did the transfer case which took almost 2 qt... Seem right?

Just did mine as well and my volumes were similar. I feel like the factory under fills by a little bit. IMO, just fill until it's coming out of the fill port on the diff cover and call it a day, have a beverage.

 

[roaniecowpony]

What fluid weights are you Rubicon owners using?

 

[Remorseless]

What fluid weights are you Rubicon owners using?

I've run Lucas 85W140 for a number of years now. Local gear shop recommended it to me a long time ago and I've had good results with it. I tend to change my fluid more often than necessary - every 18mo to 2 years, even with low miles.

 

[CarbonSteel]

What fluid weights are you Rubicon owners using?

75W-110 in the front (50/50 mix of 75W-90 and 75W-140)

75W-140 in the rear

 

[Remorseless]

@Rhinebeck01 not sure what your HaHa means. Do you not like [Banned Site] or do you not think I should do 75W90 front and rear? I've done quite a lot of reading. I have towed some dirt in a HomeDepot rental trailer one time but I really never tow. I am going down to Badlands to off road next month though. Change to 140 prior or just wait till next change?

So... how come I can't type Way-a-life as one word? It comes up [Banned Site] Why the F does it do that? That guy is great and his channel is great.

You'll be fine with 75w90. Just make sure if you have a limited slip your fluid had limited slip additive in it already or you added the limited slip additive after the fact. I would not expect issues with that fluid weight.

The banned site thing is because there's internet drama between forums or something. Trolling and shit talking and what have you.

 

[dmen]

Thanks @Remorseless.

 

[CarbonSteel]

Not to rain on anyone's parade or advice for viscosity recommendations, but, I'll go ahead and be that guy:

1. Given the heat these new Dana 44 Advanteks generate, I would not run 75W-90 in either the front or the back. I would run no less than 75W-110 in the front and 75W-140 in the rear.

2. Note that any recommendation that FCA gives is based SOLELY on CAFE and the need to MAXIMIZE MPG. Maximizing MPG and axle longevity do not equal each other.

3. Dana recommends 75W-140 in the front and the rear and I would take the recommendation of the axle designer and builder over FCA any day.

Dana 44 Front Axle Specifications - https://media.spicerparts.com/cfs/f...SHEET-JL-FRONT-UD44A-42019.pdf?store=original

Dana 44 Rear Axle Specifications - https://d3qx1uccksbb2n.cloudfront.net/docs/SPECSHEET-JL-REAR-UD44A-D44A-42019.pdf

 

[jason0341]

Not to rain on anyone's parade or advice for viscosity recommendations, but, I'll go ahead and be that guy:

1. Given the heat these new Dana 44 Advanteks generate, I would not run 75W-90 in either the front or the back. I would run no less than 75W-110 in the front and 75W-140 in the rear.

2. Note that any recommendation that FCA gives is based SOLELY on CAFE and the need to MAXIMIZE MPG. Maximizing MPG and axle longevity do not equal each other.

3. Dana recommends 75W-140 in the front and the rear and I would take the recommendation of the axle designer and builder over FCA any day.

Dana 44 Front Axle Specifications - https://media.spicerparts.com/cfs/f...SHEET-JL-FRONT-UD44A-42019.pdf?store=original

Dana 44 Rear Axle Specifications - https://d3qx1uccksbb2n.cloudfront.net/docs/SPECSHEET-JL-REAR-UD44A-D44A-42019.pdf

What disadvantages would come of running the 75W-90? Asking because I came across his YouTube video and went with that gear lubricant as well. Now two weeks later I think I’m hearing a whining noise from my rear.

Thanks

 

[rockadile]

Not to rain on anyone's parade or advice for viscosity recommendations, but, I'll go ahead and be that guy:

1. Given the heat these new Dana 44 Advanteks generate, I would not run 75W-90 in either the front or the back. I would run no less than 75W-110 in the front and 75W-140 in the rear.

2. Note that any recommendation that FCA gives is based SOLELY on CAFE and the need to MAXIMIZE MPG. Maximizing MPG and axle longevity do not equal each other.

3. Dana recommends 75W-140 in the front and the rear and I would take the recommendation of the axle designer and builder over FCA any day.

Dana 44 Front Axle Specifications - https://media.spicerparts.com/cfs/f...SHEET-JL-FRONT-UD44A-42019.pdf?store=original

Dana 44 Rear Axle Specifications - https://d3qx1uccksbb2n.cloudfront.net/docs/SPECSHEET-JL-REAR-UD44A-D44A-42019.pdf

So why are you running 75W-110 in the front? ? Given your anal-retentiveness with lubricants, I figured you'd be following their recommendations.

 

[Remorseless]

What disadvantages would come of running the 75W-90? Asking because I came across his YouTube video and went with that gear lubricant as well. Now two weeks later I think I’m hearing a whining noise from my rear.

Thanks

75w90 will in general be thinner at higher temperature and therefore will lubricate less well and will cause the gears to run warmer. However, in my personal opinion, most folks don't drive hard enough to see the benefit of the thicker 140. Higher loads and harder acceleration are where 140 becomes much more important. I run 85w140 in my JL because it's what I ran in my JK when I had that. It was on 37s and only really ever saw trail use and was running 4.88s. It could see higher wheel speed/acceleration with a heavier load than would a stock JL that's a DD. I replaced the standard JL fluid with 85w140 mainly because it's what I had stockpiled and it's going to mainly see trail use. I also carry a number of heavy tools while trail riding.

So, TLDR - 75w90 for stock rigs, mostly DD, occasional trail use. 75w140 for heavier/built-up rigs, frequent trail use. I would recommend staying on top of fluid changes with 75w90 though, just because it is thinner, will wear out more easily.

All of this is my personal opinion, YMMV and all that.

 

[jason0341]

75w90 will in general be thinner at higher temperature and therefore will lubricate less well and will cause the gears to run warmer. However, in my personal opinion, most folks don't drive hard enough to see the benefit of the thicker 140. Higher loads and harder acceleration are where 140 becomes much more important. I run 85w140 in my JL because it's what I ran in my JK when I had that. It was on 37s and only really ever saw trail use and was running 4.88s. It could see higher wheel speed/acceleration with a heavier load than would a stock JL that's a DD. I replaced the standard JL fluid with 85w140 mainly because it's what I had stockpiled and it's going to mainly see trail use. I also carry a number of heavy tools while trail riding.

So, TLDR - 75w90 for stock rigs, mostly DD, occasional trail use. 75w140 for heavier/built-up rigs, frequent trail use. I would recommend staying on top of fluid changes with 75w90 though, just because it is thinner, will wear out more easily.

All of this is my personal opinion, YMMV and all that.

Thanks for the info. I do a ton off-roading here in Colorado. Maybe I should drain mine and replace with the Royal Purple 75w-140 instead of 75w-90 I put in a couple weeks ago.

 

[CarbonSteel]

So why are you running 75W-110 in the front? ? Given your anal-retentiveness with lubricants, I figured you'd be following their recommendations.

Because I have some left (prior to this last OC, I was running 85W-140 in both axles) AND my point was not about the front axle, but the rear which is 100% in operation while it is driven. When I run out of 75W-110, I will be using 75W-140 in both.

75W-90 = 16.0 cSt @ 100°C
75W-110 = 20.5 cSt @ 100°C
75W-140 = 25.9 cSt @ 100°C

Ergo:

75W-110 is 22% more viscous than 75W-90
75W-140 is 21% more viscous than 75W-110
But 75W-140 is 38% more viscous than 75W-90

Given that most Dana 44 M220 axles run at about 210°F at 70MPH at 85°F ambient temperature unloaded--which would you rather have in your rear axle?

 

[CarbonSteel]

What disadvantages would come of running the 75W-90? Asking because I came across his YouTube video and went with that gear lubricant as well. Now two weeks later I think I’m hearing a whining noise from my rear.

Thanks

It ***may*** be too thin to fully protect the rear axle under load and load can vary depending upon ambient temperature, speed of vehicle, load in vehicle, etc.

75W-90 was chosen by FCA because it is the thinnest which means it will give the best CAFE MPG. With that said, your right foot and a head wind will impact MPG more than rear axle viscosity ever will.

 

[jason0341]

It ***may*** be too thin to fully protect the rear axle under load and load can vary depending upon ambient temperature, speed of vehicle, load in vehicle, etc.

75W-90 was chosen by FCA because it is the thinnest which means it will give the best CAFE MPG. With that said, your right foot and a head wind will impact MPG more than rear axle viscosity ever will.

Thanks for the info. Would it best to switch both back to 75-140 or could I leave the front at 75-90?

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