TRANSMISSION FLUID change or not?

[joeyjoejoe285]

My 2018 JLU Sahara has almost 126K miles on it. I asked the dealer service to do change the transmission fluid. They said they would not recommend doing it because of the mileage, it has not been done before and there are no issues. Does this make sense?

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[NWJeepr]

Yes, this can make sense.

New fluid contains high levels of detergent. Your old fluid has used up a lot of its detergent properties over time. There can be crud in the transmission from the miles and time of use, including varnish and other debris that new fluid can unseat or dissolve into the fluid. If large enough, it can clog passages in the transmission and cause issues.

New fluid isn't going to rebuild the transmission at this point, the damage has already been done by running the original fluid to 126k. So, that's why shops basically say you do this at your own risk and if the transmission isnt' having problems, it could be wise to just let it live out the rest of its life on the original fluid.

I'd want to know the quality of the existing fluid at this point. If it's dark and sludgy, the transmission might already be done. But if it's relatively clean and isn't burnt, chances are better a fluid change might actually help.

 

[CarbonSteel]

This is an old wives' tale that never dies. In the end, IF a fluid change causes the transmission to fail--it was going to fail anyway. Additionally, transmission fluid contains additives related to lubricity and viscosity stabilization and while it contains small amounts of detergents (about 1/5 that found in engine oil), it is typically not going to "strip" the material from the clutches.

This is because there is no combustion happening in the transmission which degrades additives and detergents; therefore, the additive and detergent levels are typically stable throughout the life of the fluid so new fluid is not "stronger". The new fluid can improve shifting and temperature control so changing it can help versus hurt.

 

[LukeDagny]

This is an old wives' tale that never dies. In the end, IF a fluid change causes the transmission to fail--it was going to fail anyway. Additionally, transmission fluid contains additives related to lubricity and viscosity stabilization and while it contains small amounts of detergents (about 1/5 that found in engine oil), it is typically not going to "strip" the material from the clutches.

This is because there is no combustion happening in the transmission which degrades additives and detergents; therefore, the additive and detergent levels are typically stable throughout the life of the fluid so new fluid is not "stronger". The new fluid can improve shifting and temperature control so changing it can help versus hurt.

This reminds me of the Toyota Tundra I once owned. That transmission was "sealed for life", unless it was used it for towing. The bad part, changing fluid and refilling was very complicated. Only about half the fluid drained out and was replaced.

My later reading indicated that Toyota wanted to reduce the amount of waste created during the lifetime of a vehicle. Sealed for life will reduce the creation of a lot of used fluids.

I tend to keep vehicles for a long time and high mileage, so I'm a firm believer in changing fluids on a regular basis.

 

[Rhinebeck01]

8 Speed Tranny on a 2018 JL .... Flushed with BG Machine / BG Fluid used... Tranny had 98,500..

Check out the before and after pics of the deed..

Before

After

 

[58Willys]

An experienced transmission tech told me if you have an automatic tranny with about 75k+ on it and have never change the fluid, change fluid but don’t power flush it. Drain and fill only, several times if needed. Flushing has a tendency to flush metal sludge into places it shouldn’t be. I know someone who flushed a Subaru tranny with 140k on it, and it died a very short time later.

 

[alphawolff]

An experienced transmission tech told me if you have an automatic tranny with about 75k+ on it and have never change the fluid, change fluid but don’t power flush it. Drain and fill only, several times if needed. Flushing has a tendency to flush metal sludge into places it shouldn’t be. I know someone who flushed a Subaru tranny with 140k on it, and it died a very short time later.

Flushing should never be done under any circumstance. That was shitty 3-party companies like BG selling tools to dealerships for up sales.

Drain it, change the filter, fill it. That's it. Suggested every 60k IIRC by ZF themselves. 40k for severe duty. Stellantis doesn't suggest it because by the time it's required it's out of warranty, so they don't care.

The never change fluid or it might fail thing is just nonsense, an old wives tale type of thing.

 

[MauiSteve]

+1 drain and refill, change filter or clean strainer, whichever applies. Fresh clean fluid is better than old fluid. If you are really worried do it twice separated by a few hundred miles.

 

[Rhinebeck01]

Just a follow-up to my earlier post.. The BG flush machine was only used as a tool lets say, to take the old ATF out and at the same time supplied new ATF to the pan .......while visually being able to actually monitor the fluid going in and out... The pump in the transmission did/does all the work to push ATF through all.

No BG cleaning solution was used for this service. BG machine was just used in the removal process of all old fluid in tranny and add of new fluid pretty much simultaneously.

Yes, BG fluid was used for the replacement fluid.

Anyway, actual BG Service was not performed, but I did use the BG machine and BG ATF. My first post with pics does give one the visual lets say that the fluid was indeed in need of changing..

Whether to use a machine to do the remove/add process is always a debated topic lets say... 8-)

 

[Vinman]

An experienced transmission tech told me if you have an automatic tranny with about 75k+ on it and have never change the fluid, change fluid but don’t power flush it. Drain and fill only, several times if needed. Flushing has a tendency to flush metal sludge into places it shouldn’t be. I know someone who flushed a Subaru tranny with 140k on it, and it died a very short time later.

I agree with just drain and fill versus a power flush. I’ve known a couple of guys over the years that had a power flush done and the tranny died shortly afterwards. (Not saying they weren’t going to die regardless).
One guy ended up with a tranny housing that had to be replaced due to how badly it was damaged.
Drain and refill only for me.

 

[Heimkehr]

My 2018 JLU Sahara has almost 126K miles on it. I asked the dealer service to do change the transmission fluid. They said they would not recommend doing it because of the mileage, it has not been done before and there are no issues. Does this make sense?

No, it doesn't make sense.

My selling dealer also refused to perform the service, leaning heavily on the [fictitious, IMO] "Lifetime fill" language evident in the Owner's Manual.

ZF themselves recommend this service at ~60K miles. So, I found this thread, purchased the related supplies, and got to work.

To my way of thinking, the dealers just want to get the vehicle to the end of the Powertrain warranty -- coincidentally, also 60K miles -- after which, they needn't care.

This reminds me of the Toyota Tundra I once owned. That transmission was "sealed for life", unless it was used it for towing. The bad part, changing fluid and refilling was very complicated. Only about half the fluid drained out and was replaced.

The system capacity the ZF 8HP (aka 850RE) in the Wrangler is approx. 9 quarts, of which only 5.5 quarts or so will drain out after the pan is removed. That's why at least two drain & refills (three is best) are recommended in order to maximize the replacement of old fluid with new. That's what I did, driving the vehicle 1K miles in between each DIY service.

 

[CarbonSteel]

Flushing should never be done under any circumstance. That was shitty 3-party companies like BG selling tools to dealerships for up sales.

Drain it, change the filter, fill it. That's it. Suggested every 60k IIRC by ZF themselves. 40k for severe duty. Stellantis doesn't suggest it because by the time it's required it's out of warranty, so they don't care.

The never change fluid or it might fail thing is just nonsense, an old wives tale type of thing.

 

[CarbonSteel]

No, it doesn't make sense.

My selling dealer also refused to perform the service, leaning heavily on the [fictitious, IMO] "Lifetime fill" language evident in the Owner's Manual.

ZF themselves recommend this service at ~60K miles. So, I found this thread, purchased the related supplies, and got to work.

To my way of thinking, the dealers just want to get the vehicle to the end of the Powertrain warranty -- coincidentally, also 60K miles -- after which, they needn't care.



The system capacity the ZF 8HP (aka 850RE) in the Wrangler is approx. 9 quarts, of which only 5.5 quarts or so will drain out after the pan is removed. That's why at least two drain & refills (three is best) are recommended in order to maximize the replacement of old fluid with new. That's what I did, driving the vehicle 1K miles in between each DIY service.

Here is a matrix to visualize what you are describing:

 

[CarbonSteel]

Whether to use a machine to do the remove/add process is always a debated topic lets say... 8-)

Not a direct response to @Rhinebeck01, but the issue with the "flush" machines on modern transmissions is two-fold:

1. The transmission has to be between a certain temperature range for all of the solenoids and valves to actuate and allow the fluid to completely flow. None of the dealers that I spoke with could tell me how that was achievable since the engine would not be running.

2. They could not tell me how they would not overpressure the system and damage some of the solenoids/valves.

Ergo--hard pass on the dealer--which aside from 2 of the 5, that I chatted with insisted the ZF8 was lifetime fill. To which I retorted--which means what? Until it fails?

The ZF8 is one of the easiest dump and fills you can do and if you replace the pan with a drain plug version, future transmission maintenance is a snap.

I wish the 10R60 on my Bronco was that easy...that nice exhaust pipe will brand you every time when checking the fluid levels.

 

[LukeDagny]

This thread has got transmission service on my radar. I'm at 35K miles and plan to drain and fill at 40K.

For those that have serviced their transmissions, is the drain pan gasket reusable, like the differentials?

EDIT: I just read the thread, by Carbon Steel, linked above. It has all the information I need.

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