Automatic Transmission fluid change interval s on 2021 JT

[ShadowsPapa]

In any case, I'm having a dealer transmission fluid service with my next oil change as I just passed 60K (no issues). I'm in AZ and the heat here/environment is extreme so a little preventative maintenance is better than $3500 or more for a new ZF.

60K miles where you live and drive (the heat and hills) is very reasonable thinking.

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[BearFootSam]

From my memory over the years - 175-225 is pretty normal and ok. Even 240 isn't "I'm KILLING IT!" area.
Old school ATF will sort of "cook" above 240 and that's why you see some transmissions with a "varnish" inside - a brown stuff that looks sort of like the old varnish used on sewing machine cabinets and furniture. And it discolors parts, and can eventually build up if you keep running it above that. Periodic hits of 240 aren't destroying it, but if you run there too often, that's where you really need to get into more frequent changes because with each hit to 240 or above, you are "removing" more of those additives.
That's the older stuff.....

Modern synthetic fluids can handle hitting 250 without worry (but then you get into what about the seals? Hopefully modern seal materials, too)

I used to view 250 and above danger territory, today to me I don't like it, but I'm not destroying it but I use that as a point I'd rather not touch.
I view 250 as "time to take control and drop the temps.
But with modern fluids even that isn't the danger point any more.
Real life example - Valvoline MaxLife Dex/ Merc ATF can easily withstand extreme temperatures of 280*F for up to an hour.
Dexron 6 is rated to run up to 285 degrees.

You should be able to assume that the ZF fluid can do over 250.

I'd not do that. I would try hard to keep it under 250, 240 is sort of my watch point but then I'm basing that on the old school ATFs so my reactions are still based on the red ATF we are familiar with.
I suspect, like Hootbro said in another post, the sensor is in or around the valve body so it's getting some of the warmest fluid, however, if that TC isn't locked and it's doing it's torque converting, temps in it may be hotter.
A lot of shifting adds to heat, TC working - adds to heat, hard pulls, more heat because of the load on the gears shearing the fluid generating heat.

Modern fluids are nothing like the Type A, Type F, early Dexron and other fluids - these can handle a heck of a lot more, but only the driver knows the real use that vehicle has seen. Hard use is hard use - it wears things, contaminates fluid and "uses up" the additives.
Highway use without towing, little gear hunting is a different animal. You can go farther.
Only the driver knows. Books are guidelines.

Do keep in mind, if you look it up, you're going to find people posting the numbers they've known or been told over the years based on the red ATFs like the earlier Dexron numbers. So all over the web you are likely to see people saying over 220 is killing it. No, even then it really wasn't, but today it's even less of a worry. That's the trouble with the internet...... the old numbers keep coming forward instead of being current with modern tech.
It's wild the people STILL today posting stuff from that old fluid. It's almost as bad as people still insisting we need high zinc levels (not understanding it's not even the zinc that does the protecting)

Anyway, old school red stuff, early Dexron numbers- keep below 250, 240 should be a limit.
Modern stuff - 250 isn't killing it. The fluid can handle that and more. But temper that with the sort of use you are giving that vehicle. If it's running that hot, you are stressing the transmission a bit - meaning wear and where do the bits that "wear" off of the parts go? Not out into the air.

Fortunately the JT's AT cooler is dialed in from my observations. It's a rare day that my AT temps get past 205 degrees. The highest temps I've seen were nearing 225, and that was very briefly while towing a trailer, with a full bed and two passengers climbing a steep mountain grade into a headwind. In every case the temperatures have climbed above 205, they've dropped rapidly after whatever the brief high load scenario was.

Taking advantage of the auto-stick function (per the manual) is the easiest way to control high temperatures, even though the 8HP is darn good about not hunting. I couldn't say the same of the Tacoma AT I drove, it was hunting like a field dog just rolling down the highway with nothing on board.

Though I haven't seen high temps, because I spend a great deal of time loaded and slow driving forest service roads I intend to do a fluid change about 50-60k miles.

 

[713gladiator]

I have a post on doing my first transmission drain and fill from back in November 2023 with 57,000 miles on the dash posted here:

https://www.jeepgladiatorforum.com/forum/threads/first-transmission-drain-and-fill.74234/

I am an Accountant with a very basic knowledge of vehicles.
Thank goodness for Youtube and forums like this. I was able to DIY the service in my garage.

As of September 12th, 2024, my current mileage is 68,500
No issues
Transmission runs exceptionally well
Shifts are smooth between all gears

I plan to do another transmission drain and fill at 80,000 miles which I expect to happen around November 2025. That will be 2 years from when I performed my first drain and fill. That will leave me with approx 21% of the original fluid. I'll do another drain and fill at 100,000 miles around November 2027

 

[rharr]

I have a post on doing my first transmission drain and fill from back in November 2023 with 57,000 miles on the dash posted here:

https://www.jeepgladiatorforum.com/forum/threads/first-transmission-drain-and-fill.74234/

I am an Accountant with a very basic knowledge of vehicles.
Thank goodness for Youtube and forums like this. I was able to DIY the service in my garage.

As of September 12th, 2024, my current mileage is 68,500
No issues
Transmission runs exceptionally well
Shifts are smooth between all gears

I plan to do another transmission drain and fill at 80,000 miles which I expect to happen around November 2025. That will be 2 years from when I performed my first drain and fill. That will leave me with approx 21% of the original fluid. I'll do another drain and fill at 100,000 miles around November 2027

are you doing the filter to? seems silly not to change the filter if going through all the effort.

 

[713gladiator]

are you doing the filter to? seems silly not to change the filter if going through all the effort.

Yes.
Installed a new Mopar Transmission Filter and Mopar Transmission Filter Gasket.

 

[The Yeti]

So, Ive done this on a BMW X5 ZF 8 Speed trans. Same deal except more annoying and difficult to get to everything (assuming because it was a stupid annoying to work on BMW that the engineers laugh at the mechanic when designing, but I digress) looks like same temps 30-50 c* range when checking and go through forward and reverse, neutral etc before/when checking. So next question is, can you buy just the filter? Like drop the pan swap the filter out refill check and be good to go OR likethe BMW 8 speed is the filter built in to the panamd only aftermarket pans have the removable filter? Follow up to that is parts #'s 68362041AC seems to be the pan, not sure what all comes with it...? And finally why does it not have a drain plug in the bottom of the pan dammit. Allison does it right from the factory, guess I was spoiled by that.

 

[Mr._Bill]

It's a ZF designed transmission produced in a Stellantis factory. They say the fluid is a 'lifetime' fill. Why would they spend the money to include a drain plug for the fluid that they say doesn't need changed?

 

[The Yeti]

If I had only known I would be buying a Gladiator 1 day rewind back a year I would've kept the pan from the X5 to see if it is the same. (I used a Dorman replacement with a drain plug for quick future drain and fills on that one) if that pan would fit the same as this one it would be a perfect option for the Gladiator AND it has a replaceable filter with the magnets in the pan in various spots too.
Does the Mopar pan have a removable filter then? Replaceable separate from the pan & you can actually buy the gasket separately? Curious on how many liters for the drain and fill too...think 6 to be safewhen double checking after the fact

 

[Hootbro]

Does the Mopar pan have a removable filter then? Replaceable separate from the pan & you can actually buy the gasket separately?

Gladiator has a steel pan (no drain plug) with a replaceable filter and reusable pan gasket.

FWIW, the ZF 8sp plastic pans with integral filter will fit but removes the point of having the steel pans for off road protection.

 

[The Yeti]

Gladiator has a steel pan (no drain plug) with a replaceable filter and reusable pan gasket.

FWIW, the ZF 8sp plastic pans with integral filter will fit but removes the point of having the steel pans for off road protection.

Well thats worth quite a bit actually. Good point on the plastic vs steel and off road. AND nice ti know they will fit, I dont rock crawl but winter snow wheeling I mean could potentially do some damage but 'maybe' not... famous last words. A skid plate and the cheap trans pan would give the best of both worlds though. BUT, the fact that the fluid might be replaced once or twice would swing me towards dropping the pan putting new filter in bolting it back up and filling it up. If I can reuse the pan amd gasket then thats probly the way to go. Honestly its not that bad a job just takes some time and best done in the cooler weather and winter is coming... personally I found filling with the temp at 35-38 degrees celcius worked well enough in the X5 when I did it in my cold ass garage on 4 ramps. I didnt do the spin the wheels in 1st and 2nd gear part like that video showed as that wasnt the process for the BMW with the same/similar ZF 8 speed and it turned out well.

 

[Hootbro]

Well thats worth quite a bit actually. Good point on the plastic vs steel and off road. AND nice ti know they will fit, I dont rock crawl but winter snow wheeling I mean could potentially do some damage but 'maybe' not... famous last words. A skid plate and the cheap trans pan would give the best of both worlds though. BUT, the fact that the fluid might be replaced once or twice would swing me towards dropping the pan putting new filter in bolting it back up and filling it up. If I can reuse the pan amd gasket then thats probly the way to go. Honestly its not that bad a job just takes some time and best done in the cooler weather and winter is coming... personally I found filling with the temp at 35-38 degrees celcius worked well enough in the X5 when I did it in my cold ass garage on 4 ramps. I didnt do the spin the wheels in 1st and 2nd gear part like that video showed as that wasnt the process for the BMW with the same/similar ZF 8 speed and it turned out well.

I have done the job twice on the ground on two separate Gladiators. I just used a Mity-Vac and sucked out the fluid through the fill/level port before dropping the pan and changing the filter.

The OEM FILTRAN made filter can be hard to source sometimes, so it behooves to plan ahead for sourcing that. I have also used a Crown Automotive aftermarket filter with no issue.

While not mentioned the OEM instructions, it helps to remove the frame crossmember. Then when dropping the pan down, you want to twist it 45 degrees left after you break the seal and then move towards the rear on the passenger side at the same 45 degree angle to clear the exhaust cross pipe.

 

[The Yeti]

I had to modify a torx bit and use a special thin ratchet style bit holder ratchet to get one bolt on the BMW and figured that out the hard way mid job. Luckily I had the tool and equiptment in the shop to modify the tools on the fly. Thanks for that tip, always good to know that stuff in advance.
Maybe I missed it but how many quarts to drain and fill? Looking back at my orderfor the ZF 8 before I ordered 7 and had a little bit left over

 

[Hootbro]

Maybe I missed it but how many quarts to drain and fill? Looking back at my orderfor the ZF 8 before I ordered 7 and had a little bit left over

First one I did, needed 6.5 liters. Second one need just 5.5 liters. The longer it sits cold, the more that drains back out of the torque converter into the pan sump.

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