First Transmission Drain and Fill

[Viper501]

This may be redundant but https://www.fcpeuro.com/blog/how-to-service-a-zf-8hp-transmission

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[whysoserious]

Interesting... have you figured out at which fluid change number the "new" fluid you are putting in your transmission becomes the new "percent of old fluid remaining"? Or is this a new variant of Zeno's Paradox?

 

[GoHack]

First time automatic transmission owner here.

First of all, I've always own manual transmissions w/my Jeeps, so I do know how to use them.
With that said, this past summer I bought a new 2024 Rubicon w/a 6 speed manual.
After around 1500 miles, the transmission started grinding when I would downshift from 4th to 3rd.
I brought her in, and they confirmed the noise, including draining the transmission oil and finding metal chips. When they pulled the transmission, they also checked the clutch assembly and found a broken spring there. So, it looks like they still have problems w/them on the JLs.

They ordered a new transmission/clutch assembly, which took a month and a half to get and when they finally got them, they installed them, and I picked her up.
I was able to look at everything while up on the lift, checking to make sure everything looked OK, including the mountings bolts.
Sorry, but I've had issues in the past where mechanics left bolts and such off on things.
Thanked the mechanic for his work.

Driving her, including some offroad, everything seemed to be OK, but w/in a week, some error lights came on. I brought her back in, and after two weeks they determined that a sensor on the clutch petal went bad. They replaced it, but it required tearing the dash apart. I got her back w/no more error lights but was bothered by the tearing of the dash apart, so I traded her in at a loss for a new Gladiator (Rubicon), but w/an automatic transmission this time, my very first.
With Jeep's mark downs, I saved something like $13K on her. Otherwise, I would never have bought the Gladiator.


I've known a lot of people over the years who owned automatics, which failed on them, no matter the mileage or conditions. As I saw them, they were junk, and so I never wanted one. I didn't trust them.
Then Allison came out w/their transmission for diesel GM trucks. Reading about it I was impressed, especially w/its external spin on oil filter rather than some small dinky little so-called filter that automatics use to come with.

Reading up on Jeeps ZF, it too impressed me and the reviews on it, and especially the large oil filter that it comes with, though it is a part of the cover, a plastic one no less.
So, I bit the bullet and got it.

That said, being new to automatics, I'm nervous. How do you break them in?
I did around 500 miles local driving, including some offroad, taking it easy driving, but come Thanksgiving, I had to go on a long trip to visit family. Before leaving, I went and changed the engine oil/oil filter. The dealer uses Pennzoil Full Synthetic 0W-20 Motor Oil, which is said to be good oil, made from natural gas, but went w/an Amsoil engine oil filter rather than OEM.

I drove over 1900 miles on the interstate but kept her at the speed limit using cruise control. I was in no hurry.
My RPMs averaged around 2K, when doing 65 to 70 mph, but when I would come up to a hill, she would down shift w/the RPMs jumping up to 3 to 4K. Is this OK w/an automatic transmission, as well as the engine, w/only 500 miles?

Other than that, the transmission seems to work OK and shifted smoothly and quietly.
Oh, I averaged around 18.5 mpg w/the V6/automatic transmission, doing 65 to 70 mph. After all, it's the Rubicon w/4.11's and 33' AT tires.

I'm already thinking about maybe doing a transmission oil/filter change at around 10K. The idea is to remove the break-in material for some nice clean oil.

Sorry for my long posting here, and thanks.

 

[ShadowsPapa]

First time automatic transmission owner here.

First of all, I've always own manual transmissions w/my Jeeps, so I do know how to use them.
With that said, this past summer I bought a new 2024 Rubicon w/a 6 speed manual.
After around 1500 miles, the transmission started grinding when I would downshift from 4th to 3rd.
I brought her in, and they confirmed the noise, including draining the transmission oil and finding metal chips. When they pulled the transmission, they also checked the clutch assembly and found a broken spring there. So, it looks like they still have problems w/them on the JLs.

They ordered a new transmission/clutch assembly, which took a month and a half to get and when they finally got them, they installed them, and I picked her up.
I was able to look at everything while up on the lift, checking to make sure everything looked OK, including the mountings bolts.
Sorry, but I've had issues in the past where mechanics left bolts and such off on things.
Thanked the mechanic for his work.

Driving her, including some offroad, everything seemed to be OK, but w/in a week, some error lights came on. I brought her back in, and after two weeks they determined that a sensor on the clutch petal went bad. They replaced it, but it required tearing the dash apart. I got her back w/no more error lights but was bothered by the tearing of the dash apart, so I traded her in at a loss for a new Gladiator (Rubicon), but w/an automatic transmission this time, my very first.
With Jeep's mark downs, I saved something like $13K on her. Otherwise, I would never have bought the Gladiator.


I've known a lot of people over the years who owned automatics, which failed on them, no matter the mileage or conditions. As I saw them, they were junk, and so I never wanted one. I didn't trust them.
Then Allison came out w/their transmission for diesel GM trucks. Reading about it I was impressed, especially w/its external spin on oil filter rather than some small dinky little so-called filter that automatics use to come with.

Reading up on Jeeps ZF, it too impressed me and the reviews on it, and especially the large oil filter that it comes with, though it is a part of the cover, a plastic one no less.
So, I bit the bullet and got it.

That said, being new to automatics, I'm nervous. How do you break them in?
I did around 500 miles local driving, including some offroad, taking it easy driving, but come Thanksgiving, I had to go on a long trip to visit family. Before leaving, I went and changed the engine oil/oil filter. The dealer uses Pennzoil Full Synthetic 0W-20 Motor Oil, which is said to be good oil, made from natural gas, but went w/an Amsoil engine oil filter rather than OEM.

I drove over 1900 miles on the interstate but kept her at the speed limit using cruise control. I was in no hurry.
My RPMs averaged around 2K, when doing 65 to 70 mph, but when I would come up to a hill, she would down shift w/the RPMs jumping up to 3 to 4K. Is this OK w/an automatic transmission, as well as the engine, w/only 500 miles?

Other than that, the transmission seems to work OK and shifted smoothly and quietly.
Oh, I averaged around 18.5 mpg w/the V6/automatic transmission, doing 65 to 70 mph. After all, it's the Rubicon w/4.11's and 33' AT tires.

I'm already thinking about maybe doing a transmission oil/filter change at around 10K. The idea is to remove the break-in material for some nice clean oil.

Sorry for my long posting here, and thanks.

Drive it like you plan on driving it. Don't baby it, but don't abuse it. Best thing for engine and transmission is to vary the speed. Don't get onto a flat highway and set the cruise at 65 and let the RPM stay steady. That's not good. Vary the RPM. Don't let the transmission hunt a lot - meaning no up and down, up and down, all within a mile or two.

As far as RPM, yes, let it wind up. Just in normal driving around here mine sees 3,000 to 4,000 rpm, sometimes a bit over 4,000, keeping our hills, especially when windy.
A load with some RPM helps force the rings out harder against the cylinder walls, taking off the microscopic high points sooner.
Best thing - don't lug it, let it decide the RPM and 4,000 is not bad for it, and don't drive a real steady speed and RPM for a while.

I bought both of mine, and just drove them like normal (but varying the speed - no cruise for a while). Oil analysis shows up nice and normal every time, transmission works like a dream (even when towing)

 

[bmoran]

I just did my first transmission service on a 2020 Gladiator Overland with 50k miles. A few things I came across:

1). I would recommend anyone doing this service to get a proper fluid extractor. I have one from Harbor Freight which was $90. Makes it WAY easier. I was able to extract 5.5L of fluid (and see exactly how much I extracted) before I dropped the pan. There was only a few tablespoons of fluid left in the pan. Without the extractor, this job gets messy.

2). One of the pan bolts snapped on me. I’m an experienced mechanic - this wasn’t me being a goober. It was super corroded at the top of the threads and snapped with minimal force. There were three other bolts that had significant corrosion while the rest were super clean. After sleeping on it I’m pretty sure this was galvanic corrosion. Turned an easy job into a PIA. I’d recommend applying anti seize to the threads - especially and liberally where the threads meet the bolt head.

3). Unsure if I have a different config than others but there is an exhaust pipe running right under my pan. I looked online to see if others encountered this but couldn’t find anything. At first it appears that you can’t remove the pan without disconnecting the exhaust. But if you spin the pan 90 degrees it just barely comes out. (Without the extractor mentioned above, spinning that pan with fluid inside will get really messy.)

4). After reinstalling the pan, I was only able to put in four liters of fluid. Confirming that Maximus Gladius’ directions on filling are spot on. Once you start up the motor, the transmission will suck up another 1.5L or so of fluid while in park. I’ve done a lot of fluid changes and this was the most complicated.

 

[Stan H]

I just did my first transmission service on a 2020 Gladiator Overland with 50k miles. A few things I came across:

1). I would recommend anyone doing this service to get a proper fluid extractor. I have one from Harbor Freight which was $90. Makes it WAY easier. I was able to extract 5.5L of fluid (and see exactly how much I extracted) before I dropped the pan. There was only a few tablespoons of fluid left in the pan. Without the extractor, this job gets messy.

2). One of the pan bolts snapped on me. I’m an experienced mechanic - this wasn’t me being a goober. It was super corroded at the top of the threads and snapped with minimal force. There were three other bolts that had significant corrosion while the rest were super clean. After sleeping on it I’m pretty sure this was galvanic corrosion. Turned an easy job into a PIA. I’d recommend applying anti seize to the threads - especially and liberally where the threads meet the bolt head.

3). Unsure if I have a different config than others but there is an exhaust pipe running right under my pan. I looked online to see if others encountered this but couldn’t find anything. At first it appears that you can’t remove the pan without disconnecting the exhaust. But if you spin the pan 90 degrees it just barely comes out. (Without the extractor mentioned above, spinning that pan with fluid inside will get really messy.)

4). After reinstalling the pan, I was only able to put in four liters of fluid. Confirming that Maximus Gladius’ directions on filling are spot on. Once you start up the motor, the transmission will suck up another 1.5L or so of fluid while in park. I’ve done a lot of fluid changes and this was the most complicated.

Engine off and 5.5L came . Then only 4 back in . Something doesn't add up . Should have been able to get 5.5L back in the pan

 

[bmoran]

I was surprised by the difference. My guess is that the cause of the difference is the engine being off. Once I started up the engine, I was able to put in another 1.5 L. I’ll assume this is because the transmission pump sucked fluid up into the transmission internals.

This process above (and the subsequent putting it in gear and getting it up to temperature) is something I haven’t seen before. Hence my comment about this being more complicated than other transmissions I’ve done.

 

[ShadowsPapa]

I was surprised by the difference. My guess is that the cause of the difference is the engine being off. Once I started up the engine, I was able to put in another 1.5 L. I’ll assume this is because the transmission pump sucked fluid up into the transmission internals.

This process above (and the subsequent putting it in gear and getting it up to temperature) is something I haven’t seen before. Hence my comment about this being more complicated than other transmissions I’ve done.

After every transmission rebuild I did - I'd fill it, run the engine, and keep adding fluid until full, then ran through all gears (wheels off the ground) and then back into Park (neutral for TF transmissions) engine running and checked it again. Servos, clutch packs, made sure they were all wet and had fluid, then checked after a while. When things start out dry and empty, takes a while to fill the converter and all of the passages in the valve body, servos for bands, accumulators, clutch packs.
Fluid always was checked warm.
I've never just started one and checked the fluid. Always warmed it up, most advise to check it warm. Toyota has specific temperatures for defining warm and cold fluids.

 

[Maximus Gladius]

Doing this, or most anything for the first time, has that “I don’t know what I don’t know” factor until it’s it’s done a couple, three times, then is super easy, can be done blindfolded.

You did good figuring it out and you got it all back in there.

 

[Stan H]

After every transmission rebuild I did - I'd fill it, run the engine, and keep adding fluid until full, then ran through all gears (wheels off the ground) and then back into Park (neutral for TF transmissions) engine running and checked it again. Servos, clutch packs, made sure they were all wet and had fluid, then checked after a while. When things start out dry and empty, takes a while to fill the converter and all of the passages in the valve body, servos for bands, accumulators, clutch packs.
Fluid always was checked warm.
I've never just started one and checked the fluid. Always warmed it up, most advise to check it warm. Toyota has specific temperatures for defining warm and cold fluids.

Try and explain to me the 5.5liters out. And then only 4 back in until starting then 1.5L more. If the pan was holding 5.5L when drained it should hold 5.5L without starting it . That dont make sense to me

 

[Hootbro]

Try and explain to me the 5.5liters out. And then only 4 back in until starting then 1.5L more. If the pan was holding 5.5L when drained it should hold 5.5L without starting it . That dont make sense to me

If he did it stone cold and sitting for a good bit, about 1.5 L or quarts will gravity drain out before it is level with the fill plug with the remaining left to be extracted.

I get it though, what he wrote does make it sound like the whole 5.5L was extracted with the tool.

 

[Stan H]

If he did it stone cold and sitting for a good bit, about 1.5 L or quarts will gravity drain out before it is level with the fill plug with the remaining left to be extracted.

I get it though, what he wrote does make it sound like the whole 5.5L was extracted with the tool.

I guess I see what your saying . YES your right it did sound that way .

 

[ShadowsPapa]

Try and explain to me the 5.5liters out. And then only 4 back in until starting then 1.5L more. If the pan was holding 5.5L when drained it should hold 5.5L without starting it . That dont make sense to me

Quite possible - things will drain back after sitting. So unless he did it hot right after driving it............

 

[bmoran]

You got it right. I drained the fluid when the vehicle was cold. Out came 5.5L. Then I filled it until fluid came out the fill hole. It took 4L. I then started the vehicle and was able to put in another 1.5L before it started coming out the fill hole. And then I went through the process of running it through the gears and bringing the transmission up to speed. And then topped off the fluid.

I was trying to communicate (not very well apparently) the significant gap between the initial fill without engine running and what happens as soon as the engine is started. To help the next guy doing this.

 

[Maximus Gladius]

What t

You got it right. I drained the fluid when the vehicle was cold. Out came 5.5L. Then I filled it until fluid came out the fill hole. It took 4L. I then started the vehicle and was able to put in another 1.5L before it started coming out the fill hole. And then I went through the process of running it through the gears and bringing the transmission up to speed. And then topped off the fluid.

I was trying to communicate (not very well apparently) the significant gap between the initial fill without engine running and what happens as soon as the engine is started. To help the next guy doing this.

What temp did you settle with for your oil level?

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