ZF8 50K Mile Transmission Service -- DIY How-To Instructions

[The Chad]

So I saw where several others had reported the fluid was low from the factory. I'm curious if somebody has the time to measure the expansion difference between 5qts @ 86* and 122* fahrenheit.

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[GATORB8]

FYI, I did Mopar fluid since I'm still under warranty (probably unnecessarily) and I have the electric clutch pack in mine.

Rock Auto had it in stock for $24.79/qt.

 

[blnewt]

FYI, I did Mopar fluid since I'm still under warranty (probably unnecessarily) and I have the electric clutch pack in mine.

Rock Auto had it in stock for $24.79/qt.

What JL models have the electric clutch pack? I assumed we all got the same ZF model??

 

[GATORB8]

What JL models have the electric clutch pack? I assumed we all got the same ZF model??

4xe, clutch and electric motor instead of TC.

 

[OldBlue]

@CarbonSteel - thanks for documenting this as you have. My wife's '20 just turned 35k, so I'll probably be doing this next year on hers (mine has the manual trans) and it's good to see how you did it and the results of the testing.

 

[blnewt]

4xe, clutch and electric motor instead of TC.

Nice! Always find some new nuggets of info around here!

 

[CarbonSteel]

So I saw where several others had reported the fluid was low from the factory. I'm curious if somebody has the time to measure the expansion difference between 5qts @ 86* and 122* fahrenheit.

Not even sure how you would effectively and accurately do that. Mine was low and there have been others report the same.

One thing that I think leads to the fluid being low is that you need to allow the air to be purged (like from the filter and lines) and after that check the levels again. Mine was not to capacity on each change after I checked it again after 25 miles or so.

 

[CarbonSteel]

@CarbonSteel - thanks for documenting this as you have. My wife's '20 just turned 35k, so I'll probably be doing this next year on hers (mine has the manual trans) and it's good to see how you did it and the results of the testing.

Anytime! So many OEMs treat systems as a "black box" OR make it "maintenance free" so the end user does not have the data needed to make informed decisions regarding maintenance regimes.

The OEMs also have a "mission" to increase MPG and thus make some of their design/maintenance decisions around that desire. Changing the axle viscosity from Dana's recommended 75W-140 to 75W-90 is a prime example of that.

In any event, "lifetime fill" is an oxymoron at best...

 

[lashlee]

Finally got around to doing this today. Got everything setup with the drain pan, loosened the fill plug and was quite surprised at the amount of fluid that came out!! Mine was not low!!! Like @CarbonSteel noted, loosening the bolts was simple and I let it drain from the rear of the pan while I aired up the tires after wheeling yesterday. Used my Motive Products power fill to refill the fluid without effort!! I went ahead and flushed the brake fluid after I finished the pan swap/fluid fill.

Thanks again for posting this!

 

[CarbonSteel]

Finally got around to doing this today. Got everything setup with the drain pan, loosened the fill plug and was quite surprised at the amount of fluid that came out!! Mine was not low!!! Like @CarbonSteel noted, loosening the bolts was simple and I let it drain from the rear of the pan while I aired up the tires after wheeling yesterday. Used my Motive Products power fill to refill the fluid without effort!! I went ahead and flushed the brake fluid after I finished the pan swap/fluid fill.

Thanks again for posting this!

Anytime! Note that pulling the plug without the engine running will result in quite a bit of fluid coming out.

The only way to check if it is low is to bring the transmission up to temperature and with the engine running pull the plug. If fluid does not drip out, then it is low.

I assume you did the final fluid check at temperature with the engine running, right?

Also, drive it a bit and check it again. It will likely be a little low after the filter fills and system purges the air.

 

[Chocolate Thunder]

Anyone know what a dealership service department charges for this service?

 

[CarbonSteel]

Anyone know what a dealership service department charges for this service?

Here in COS it was between $700 and $800, but no one had all of the necessary parts.

CT - you can do this yourself (including dropping the skids), I did it once with help and twice alone.

 

[Chocolate Thunder]

Here in COS it was between $700 and $800, but no one had all of the necessary parts.

CT - you can do this yourself (including dropping the skids), I did it once with help and twice alone.

Thanks. There’s not much I’m not able to do. But sometimes there’s things I don’t want to do or have time to do.

 

[WrangleDangle]

I changed the filter and fluid today and not a bad job aside from having to pull two of the three MC skid plates to get to the transmission and transfer case. Loosen the pan bolts all the way around and then loosen the back bolts a little more (towards the rear of the Jeep) to allow the fluid to drain and it will be less messy. I had to rotate the pan 90° to get it out from under the 3.6L exhaust pipe. A drain plug would have made the change a breeze.

I used a Mopar filter and ZF Lifeguard 8 fluid and it took a little over 5 QTs. The two magnets in the pan had a fair amount of metal "paste" on them, but nothing that I did not expect to see after 50K miles. Note the magnets are simply held in the pan via magnetic force and are not permanently attached which makes cleaning them a breeze. There was no debris in the pan which is a good indication the clutches are not shedding material.

FCA states to snug the filter nuts and then back off 1/2 round which I did (they are locking flange nuts and new ones are included with the filter). This is so the filter can move horizontally slightly to allow for alignment of the filter nozzle into the valve body housing. I lightly lubed the o-ring on the filter with new fluid and then mounted the pan.

ZF states the pan bolts should be 12nm and FCA states 10nm, so I split the difference and went with 11nm and followed the torque sequence in the attached PDF. Although I have a new gasket, I re-used the old one because it was in great shape. I used the process documented in the attached PDF to refill and check the fluid.

I plan to run it for about 5K miles and dump the fluid again. I sent two samples off to be tested--one virgin sample of LifeGuard 8 and one of the used fluid and I will share the results here.

With all of that said, the fluid was VERY dirty as compared to the new fluid (see pictures). I would not under any circumstances run the fluid and filter for 100K miles or "lifetime" as FCA states. I think that FCA is doing a serious disservice to owners when they say "lifetime" fill--which is complete and utter bovine scatology.

EDIT: Though I had bought a pump-up sprayer to install the new fluid, it was not needed. There was more than enough room to use a Flo-tool nozzle which fit the ZF bottles with no issues:

https://smile.amazon.com/dp/B000EH4UXM/



Enjoy!

Left pan magnet:

Right Pan Magnet:

Clean Pan and Magnets + New Filter:

Old Fluid in Drain Pan:

Old Fluid on White Paper Towels:

Comparison of New and Used Fluid:

The attachment does not show the 850RE Transmission.

 

[CarbonSteel]

The attachment does not show the 850RE Transmission.

That is because it is a ZF document--FCA renamed the 8HP to 850RE. The document is fully applicable to the 850RE.

Here from Wikipedia for a 8HP, you can clearly see the main document is for the 8HP, yet in the Jeep section, it calls out 850RE:

https://en.wikipedia.org/wiki/ZF_8HP_transmission#Jeep

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