Early fluid changes: differentials, transfer case, manual transmission

[bd100]

20,000 miles, first fluid changes for each:

Back differential: Did some towing, dark fluid, plenty of metal. The drain magnet had what looked like a little sand castle on it. Lots of sparkles in the fluid, and a few larger flakes. Should have changed it sooner. I put synthetic 75W140 GL-5 in it. The manual says 75W85 but rumor has it the service manual says 75W140 if towing. Why couldn't the owner's manual have said this? Did I ruin the differential? Didn't take the cover off, not sure I know enough to judge whatever I might have found if I did.

Front differential: Much lighter fluid, much less glitter in the lube. Did some offroading, so I actually did use the front differential, but only a bit. Could have gone longer, as the owner's manual suggests. I used synthetic 75W90 GL-5 up front. No drain plug, so I used a suction gun.

Transfer case: Again, did some offroading, but not much. Clean fluid. Could have gone much longer, as the owner's manual suggests. Used synthetic ATF+4.

Manual transmission: Mildly dark, not much metal. Glad I changed it early. Towing. Used synthetic ATF+4.

The transmission and transfer case required removing and replacing some skid plates, but that's OK. I used anti-seize on install so the bolts came back out fine. Took the opportunity to install better washers than the aftermarket skid manufacturer provided, which bent on install and are already rusting.

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[just_another_guy]

Do you happen to have a factory lsd in your rear diff?

 

[Maximus Gladius]

Back differential: Did some towing, dark fluid, plenty of metal. The drain magnet had what looked like a little sand castle on it. Lots of sparkles in the fluid, and a few larger flakes. Should have changed it sooner.

Not sure if you have lockers or not but if the drain plug had that mound of magnetic sludge on it, your locker sensor magnet will too and when that’s all coated up with magnetic debris, your locker engagement and disengagement won’t work like it should.
If you like having lockers that work or you want them to work if you ever need them, pop off the diff covers, unplug the locker sensor and pull out the small torx screw holding it in and gently pull it off the magnet and out.

You’ll see that magnet will be full of metal paste coating it and that needs to be clean. The cover gasket is reusable and your only out 1.5 quarts or so but it’s chump change and now it’s all clean and you’ve had some ‘hands on’ in getting it all cleaned up proper.

With the sensor out, spray around in there with brake cleaner and wash all the metal filings and bits out. Dry it out and install it all back again. Super simple and easy and you’ll even enjoy doing it.

 

[bd100]

Yes, I should have mentioned that the back differential has a limited slip. So that's part of the darkness of the fluid.

We'll see if the back diff holds up. There is a quiet metallic swishing noise occurring back there somewhere, road speed dependent. But it doesn't (yet) depend on acceleration / coast / deceleration. Nor does it change with a hard left or right turn. Nor it I loosen the parking brake. And I raised each of the 4 tires one at a time to shake them, no looseness. And I took off the back wheels to check the rotors, no rocks or twigs stuck in there. So I don't yet know what that is.

 

[ShadowsPapa]

Go by the owner's manual. Don't go by rumor.
I checked those "rumors" a while back and most are talking the old Dana 44 of 15+ years ago, like from 2005 and so on. Even then there's mixed talk.

Our books have been out since 2019 and this is what the 2022 version says ->

they say nothing about "if towing" and so on.

Plenty of heavy heavy towing has been done on 75w85 or similar.

If there was a problem it would mean every owner would have to drop out brand new fluid and replace it if they towed.

 

[Hootbro]

Dealer Tech Authority and DANA rebuild guidelines both call out 75W-140 for towing or use in rebuild. Not rumor.

 

[Escape.idiocracy]

20,000 miles, first fluid changes for each:

Back differential: Did some towing, dark fluid, plenty of metal. The drain magnet had what looked like a little sand castle on it. Lots of sparkles in the fluid, and a few larger flakes. Should have changed it sooner. I put synthetic 75W140 GL-5 in it. The manual says 75W85 but rumor has it the service manual says 75W140 if towing. Why couldn't the owner's manual have said this? Did I ruin the differential? Didn't take the cover off, not sure I know enough to judge whatever I might have found if I did.

Front differential: Much lighter fluid, much less glitter in the lube. Did some offroading, so I actually did use the front differential, but only a bit. Could have gone longer, as the owner's manual suggests. I used synthetic 75W90 GL-5 up front. No drain plug, so I used a suction gun.

Transfer case: Again, did some offroading, but not much. Clean fluid. Could have gone much longer, as the owner's manual suggests. Used synthetic ATF+4.

Manual transmission: Mildly dark, not much metal. Glad I changed it early. Towing. Used synthetic ATF+4.

The transmission and transfer case required removing and replacing some skid plates, but that's OK. I used anti-seize on install so the bolts came back out fine. Took the opportunity to install better washers than the aftermarket skid manufacturer provided, which bent on install and are already rusting.

I haven’t looked it up- this Jeep is our first automatic so…. Anyways. If the JT manual is the same as the JK manual- amsoil synchromesh fluid was a significantly noticeable improvement over valvoline or Mopar fluid…. Also used to squat the drivers side and “over fill” the thrans a bit helps too.
If they are totally different transmissions- my apologies.

 

[bd100]

Dealer Tech Authority and DANA rebuild guidelines both call out 75W-140 for towing or use in rebuild. Not rumor.

Now wondering what the factory fill was if towing package was included.

 

[ShadowsPapa]

Dealer Tech Authority and DANA rebuild guidelines both call out 75W-140 for towing or use in rebuild. Not rumor.

So we are to ignore the book when servicing or when you decide to tow you must drop out the brand new fluid with 500 miles and swap fluid.
Nice. Almost everyone who has changed fluid then towed has a fried differential.

 

[ShadowsPapa]

Now wondering what the factory fill was if towing package was included.

But what if you add a receiver later ... Or bumper tow.
My bet is nothing bad happens. Think of all of those who tow with a ball on the bumper or later add a receiver.
Anyone who goes by the book certainly isn't ending up with trashed gears.

 

[Hootbro]

So we are to ignore the book when servicing or when you decide to tow you must drop out the brand new fluid with 500 miles and swap fluid.
Nice. Almost everyone who has changed fluid then towed has a fried differential.

A little snarky there partner.

I posted it because the data is out there from both dealer service data and OEM supplier data that 75W-140 can be used.

I am not telling anybody to not follow the OM, I just putting the info out that there is engineering data in place that supports the use of 75W-140. As to why the OM does not call it out, that is known only to them but it is not because engineering does not support the use of it.

 

[Hootbro]

Now wondering what the factory fill was if towing package was included.

I would say probably the 75W-85 grade as meeting the EPA mpg estimates is a higher priority to them.

 

[bd100]

Here is the back differential's drain plug at 20,000 miles, with a few cross country towing trips with a 2000lb trailer. It's been a few hundred miles now since I cleaned the plug and changed the fluid. I'm considering taking out the fill plug, then the drain plug, stuffing the fill into the drain as quickly as possible to preserve the new diff lube, and check the drain plug for more filings. Replace and top off. I bet I'll lose most of the new fluid even if I move quickly.

So is this a reasonable amount of break in debris? That's quite a mound of sludge with filings on top. And something back there is making noise, but it does not depend on accel / decel / coast.

 

[Blade1668]

I'm not a SME on this or really anything.... so here is my opinion on gear oil in axles.. good call to change it early. When I changed the oil in mine it was within early ownership " I didn't pull covers" I should have, but did note how little gear oil that was in them. I commented in different thread on that shortage of it being possible reason for many axle seal failure and leaking. I used Valvoline synthetic gear oil to refill around 2 times as much as I drained out. If I'm not mistaken. No leaking axle seals and at 77000 miles or so. On my list is to change transmission oil and T-case, hopefully I get around to installing front locker. Then I'll change axles gear oil again then. ? more stuff on my list of to do.
My LJ is a manual transmission it's had 3-4 transmission fluid changes done at least. The fluid was gunked up and turned dark it's at over 1/4 million miles on second clutch. In past I would change the brake fluid and power steering fluids every year or so even.

 

[bd100]

something back there is making noise, but it does not depend on accel / decel / coast.

I take that back. Now it is beginning to change depending on accel / coast. Metal scrubbing metal sound. Worse on gentle accel vs coast. Looks like a trip to the service dept is in order.

(EPA strikes again!)

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