Automatic Transmission fluid change interval s on 2021 JT

[ShadowsPapa]

Papa, you’re scaring the poor guy. It’s not hard and no, my checking my oil and pulling a sample and having a certified transmission shop do the flush did not implode my transmission. Come on now, you know my story intimately and focus needs to target the glycol contamination which will destroy every transmission it contaminates.

Not trying to scare, just a reality check. Anyone doing this should totally forget they have even seen an early transmission. Don't even think of comparing.
And yes, like the videos show, it's a lot of in and out of the cab, under the truck, back out, under, back out unless you have the monitor under the truck with you or a friend in the cab. Either way, the only real temp test is a monitor like the fellow on YT used.

If one assumes it's simple and does any comparing, they'll find out........
Start as if you've never worked on a transmission, and keep in mind if you touch the parts with a cotton cloth, you could trash the transmission. That I have seen personally. Cotton rags, rags, don't use them. Lint free cloths only. A piece of lint can lock a shuttle solid in the valve body.
Cleanliness isn't next to godliness on automatics, it IS god.

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[Maximus Gladius]

I do agree if you miss the temp window, it has to cool or, if you can, wait till the next morning to start again. But if you want a good idea how much time you have in that window, start your truck and put it on the screen that lets you see your transmission temp. Watch it and time how long the temp takes from 88-122F.

 

[Nitroexpress]

Because it IS complex. They don't really want driveway "mechanics" messing with it. The tolerances in these are crazy tight.
Have you see how you add fluid? There's no dipstick. You do it from under the vehicle
No big deal? Go watch the youtube videos of a guy doing the fluid check - it can take hours as if you miss that temperature mark, you do it again. It's a small window.
Yeah, you can do it, but you've not worked under a vehicle, watching for the correct temperature and working quickly to take a check under a truck with hot exhaust.
No, it's not as simple as switching through the gears and watching. In fact, with some of the ZF transmissions, there's things you don't want to do while doing the check and flipping through gears to get it warmed up is likely among them.
There's no dipstick for a reason, and special instructions for a reason. You see the words "pain" and "complicated" because it is.
A member has been through it.

(now he also has a trashed transmission but that may or may not be related)

Guess what - I'm a former auto tech, I used to rebuild transmissions as part of my job - I'm not messing with my JT transmission.

Thanks for the input!

I've worked under plenty of hot vehicles, but the temp checking procedure is done up top, not underneath.

I have watched the video's. This guy does exactly what I outlined as far as shifting through the gears: (start at 11:16 for shifting instruction)


I do question the method of using the built in transmission gauge vs. a 'proper' scan tool.

 

[Maximus Gladius]

88f is the temp of a really nice summer day. It takes about 10-15 min of engine running to get the transmission to warm. 122F is fricken hot and it takes about an hour of idling to get there. Checking the level doesn’t require rags getting inside so yes, one can scare themselves when it’s a non issue.

 

[WhyNotJeep]

I just got my '22 JTR and in about 6-7 years it will have 50K on it. By then I'll be ready to get a new one and I'll be in my middle 70's. Not going to even think about the tranny fluid change.

 

[Nitroexpress]

It’s the gasket and fasteners that are a one time use. Yes, the filter is fastened on the pan with nuts but unless you can get a gasket by itself, there’s no use in buying it all split up.

The oil change is super easy but you must reflash or relearn the transmission when the oil is changed and would take some gizzmo to do that.

What is your MILAGE? Would very much appreciate it if you would send off a sample of your oil to a lab so I can at least compare what “good” metal numbers look like to that of mine that imploded at 32k kms due to glycol contamination.

Great information.
- I THOUGHT the gasket and fasteners are re-usable.
- I DIDN'T know it requires a re-flash. I've seen that in none of the video's I've watched. Do you have a reference or video for this?
- I'm at about 48k Miles. I will try to get a sample sent to Blackstone.

 

[Maximus Gladius]

Great information.
- I THOUGHT the gasket and fasteners are re-usable.
- I DIDN'T know it requires a re-flash. I've seen that in none of the video's I've watched. Do you have a reference or video for this?
- I'm at about 48k Miles. I will try to get a sample sent to Blackstone.

I don’t have a reference but I had come across some info about a year ago, right after getting my truck February 2021 where I had first heard about the need to “relearn” the transmission after oil change. I searched it and found nothing. When all my troubles came to head at about 20-24k kms (transmission whine, transmission pan/gasket/fasteners finally came in, oil analysis showing glycol contamination and extreme levels of copper and iron and finding transmission shop for flush) dealership also confirmed relearn was necessary for an oil change and transmission shop also confirmed its required after flush.

 

[Nitroexpress]

Not trying to scare, just a reality check. Anyone doing this should totally forget they have even seen an early transmission. Don't even think of comparing.
And yes, like the videos show, it's a lot of in and out of the cab, under the truck, back out, under, back out unless you have the monitor under the truck with you or a friend in the cab. Either way, the only real temp test is a monitor like the fellow on YT used.

If one assumes it's simple and does any comparing, they'll find out........
Start as if you've never worked on a transmission, and keep in mind if you touch the parts with a cotton cloth, you could trash the transmission. That I have seen personally. Cotton rags, rags, don't use them. Lint free cloths only. A piece of lint can lock a shuttle solid in the valve body.
Cleanliness isn't next to godliness on automatics, it IS god.

I honestly still don't get the extreme differences being portrayed.

- You drop a pan, change a filter and gasket, bolt a pan back with proper torque spec. Don't allow any contamination. > I say No different than 'old school'.
- You fill through a filler plug rather than a dipstick tube. > I say different from 'old school' in a very minor way, and no different that myriad other gear boxes and differentials.
- Correct fill level. > I say different from 'old school' in that you must hit a specific temperature range, which is generous. 'old school' was on a dipstick at Operating temperature. You portray this differently than shown on videos, where they sit comfortable in the cab watching a monitor until the temp is reached, then go under the vehicle to do the final fill.

The biggest difference, and one you didn't mention, was the potential for a TCM re-flash/learn. I'd like to understand more about this one.

 

[Maximus Gladius]

When I approved the initial FCA investigation into what happened to my transmission, the tech dropped the pan, photos taken of the implosion damage and tech noted on the service order “oil level correct”.

Checking the oil level on this tranny is not rocket science. Some small details to know and to watch for but it’s a user friendly process.

 

[Mac]

May or may not be applicable, my MDX has a ZF 9 speed, at 50k the transmission need to be serviced, code pops up on the maintenance minder, I just did a drain and refill but the procedure is very similar with specific temperature and measuring through a port on the side of the transmission. I did not do any of that. I just drained it carefully, measured exactly what came out and put the same amount back in, then reset the minder, close to 20k miles ago no issues. If the JT needed transmission service I would do the same except drop the pan and change the filter as well. YMMV

 

[Hootbro]

For a "simple" drain, filter change and refill, I have never seen anything about having to flash or relearn for the transmission.

Doing the filter change and fluid drain/refill, is not voodoo. Just have to do your homework, watch some videos and understand completely what you are getting into. There is more info on the RAM side that has had these same transmissions for a bit longer than the JL/JT that info can be gleamed from.

90% of the job is the prep. Do it once, you will find the job was not that scary after all.

 

[Nitroexpress]

https://aftermarket.zf.com/remoteme...38411/si-zf-si-oelwechselkit-8hp-50130-en.pdf

I found the above information sheet from ZF. Here's what I glean:

- No mention of a TCM reflash or need to put it in a learn mode. (Not saying you aren't correct Kevin!)
- ZF states specifically that "flipping through the gears" is indeed part of the process.
- The filter is integrated with the pan in plastic pan applications. Mine has a metal (not aluminum) pan.

I'm still sticking with my idea that this isn't too far different from an 'old school' transmission pan drop, filter change and fluid fill. achieving the proper fluid level is important (like old school) and must be done within the designated temperature range (slightly different than old school).

 

[Hootbro]

Attached is the OEM procedures from Tech Authority. Only thing that cannot be reused is the two small nuts for the filter that thread to studs in the pan. New OEM filter will come with new nuts.

The gasket is a rubber molded into metal gasket and is reusable so long as you do not ham fist it out when removing the pan.

OEM filter part number is 68417054AB. This is the one item I would say do not go cheaper aftermarket and spend the coin for the OEM.

 

[Maximus Gladius]

https://aftermarket.zf.com/remoteme...38411/si-zf-si-oelwechselkit-8hp-50130-en.pdf

I found the above information sheet from ZF. Here's what I glean:

- No mention of a TCM reflash or need to put it in a learn mode. (Not saying you aren't correct Kevin!)
- ZF states specifically that "flipping through the gears" is indeed part of the process.
- The filter is integrated with the pan in plastic pan applications. Mine has a metal (not aluminum) pan.

I'm still sticking with my idea that this isn't too far different from an 'old school' transmission pan drop, filter change and fluid fill. achieving the proper fluid level is important (like old school) and must be done within the designated temperature range (slightly different than old school).

Specifically look for the 850RE transmission. I’m guessing the 8HP models are made in Germany??? The 850Re Is assembled in the US.

 

[jac04]

... I did not do any of that. I just drained it carefully, measured exactly what came out and put the same amount back in, then reset the minder, close to 20k miles ago no issues. If the JT needed transmission service I would do the same except drop the pan and change the filter as well. YMMV

That's kind of my plan as well. If/when I ever decide to do my JT, I'll just drain/extract fluid through the fill port, then measure & refill with the same amount. I'll do this a few times with about 50-100 miles between extractions. With the low miles I put on it, I'm not going to bother with the filter. This is the same process I use on my 5A JK. Every 25k it gets 3 extraction/refills (although it is much easier because everything is done from above through the dipstick tube).

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