Fluid in FAD compartment?

[fourfa]

I dropped in new front axle ball joints, and RCV axles (the ones that that keep the FAD) this weekend. To remove the middle axle stub (from front diff to FAD) you have to remove the FAD fork and actuator. When I did, unlike the ~15 videos I watched of people installing RCVs on various JL/JTs, some differential fluid poured out. Maybe half a cup or so - certainly not the whole contents of the diff, just some that had accumulated in there.

My guess is, some leaked past the passenger side axle seal and accumulated in the bottom of the FAD compartment, and can't really escape unless you drive at like a 45° right slope. But I suppose it could indicate a problem with the vent hose, or an axle seal problem? Obviously I will check the fluid level before I drive any significant miles (though it's likely been this way for a while). 35k miles and no drivetrain problems to report before this.

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[Vtur]

That's normal. The oil seal is toward the outer shaft. The inner one act more like a guide to help centering the shaft to the carrier. Without it, the seal can easily gets damage by the weight of the shaft on inserting.

Edit: Dana diff cover has 2 fill ports. Upper one for dry overhaul axle and lower is for drain & fill service. If you have the stock cover, recheck level after maybe 100 miles or so and add more if needed.

 

[Hootbro]

Edit: Dana diff cover has 2 fill ports. Upper one for dry overhaul axle and lower is for drain & fill service.

Using that upper fill port for a "dry" fill, does it level out eventually and is at the lower fill port when in service? Never understood exactly that recommendation from DANA on using the upper fill port and thought it was for "high pinion" angle use.

 

[Vtur]

Using that upper fill port for a "dry" fill, does it level out eventually and is at the lower fill port when in service? Never understood exactly that recommendation from DANA on using the upper fill port and thought it was for "high pinion" angle use.

Yes it leveled out. It's nearly a quart different. Some goes to the FAD and oil valley between the pinion bearing. And, same for the rear but some goes to the axle bearings. I drove about 50 mi then undo the lower plugs, and about 2oz drained out for the rear and 1oz in front. That's with the Mopar 2" lift springs with 1" spacers in the front.

 

[Hootbro]

Yes it leveled out. It's nearly a quart different. Some goes to the FAD and oil valley between the pinion bearing. And, same for the rear but some goes to the axle bearings. I drove about 50 mi then undo the lower plugs, and about 2oz drained out for the rear and 1oz in front. That's with the Mopar 2" lift springs with 1" spacers in the front.

Interesting. That may explain why the factory differential with the stamped cover seem to be under serviced when I have checked them.

 

[Vtur]

Interesting. That may explain why the factory differential with the stamped cover seem to be under serviced when I have checked them.

Yeah. I found that out too after i regeared mine when i had the steel covers. I then noticed on the Dana's torque spec sheet mentioned about the 2 fill ports. Bought the Dana's covers and i was able to tested out when i replaced my rear pinion bearing.

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