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So over the winter, I changed out the transmission fluid on my ZF 8HP. While Aston Martin has a 'lifetime fluid' policy with no servicing of the fluid planned on the vehicle life, ZF themselves post a '8yr , 50k-75k miles' service interval.
There's a couple things I wanted to achieve on this fluid change:
1. Recover/Refill as much fluid as there is
2. Pan kit and Upgrade kit if possible
3. OE or aftermarket fluid for refill
I'll format this post in those 3 sections.
#1,
You can read online that draining the fluid from the pan and refilling from the fill port will yield ~3.5Qt of fluid being swapped. This is well documented in a lot of owner forums for Dodge/RAM, BMW, Audi that also have the 8HP. Thing is, there's a LOT more fluid in the systen than that drain capacity, and some people resort to drain&fill multiple times to try to get as much 'old' fluid out and mixed in with the new. I thought this was pretty wasteful. At the same time, I did not want to remove the valve body from the transmission to get to more fluid out, and had to contend with the Torque Converter also holding fluid!
So, let's start with the drain part...
First, it's apparent from looking inside the pan (once removed) that the drain plug threads are recessed somewhat inside the pan, and that will prevent the pan from fully draining.
The procedure is quite simple, make way for the fill plug access by loosening / removing a couple heatshields, crack the fill plug open first (#8 hex), and then remove the drain plug (#10 hex). You'll get about 3.5Qt out.
Then, I removed the pan by loosening the Torx attachment bolts to first be able to break the pan off the transmission case, and carefully angle it downwards so I could catch the rest of the oil, and there was still quite a bit!
With the pan dropped, I was at about 4.1Qt recovered, so things were going well!
The next part of the process was the get up to 90% of the oil out of the rest of the system. I used a 3rd party air pressurization tool that is suited for the 6HP , 8HP and other MB transmission. The trick is to slowly pressurize at about 4psi the valve body (where oil is usually at 14psi) to get the air to displace the oil and get it overflowed and drip back in the pan. I must say this worked surprisingly well, but one must be patient and let it run its course. It takes some time initially for the air to build up into the system and fluid to come out, but once it does, it's a steady stream.
The tool itself consists of a pressure regulator, transmission valve body adapter, and air line with a valve. I found the pressure gauge on the regulator to be pretty useless because its scale is way too high for the minimal amount of air pressure needed. As you can see on the picture below, I barely get the gauge needle up for 4-5psi.
However... the thing just works great. Got about 90% of the gearbox case oil out.
Here's an animated GIF of the valve body dripping out its fluid when I feed it low pressure air:
At this point I had achieved a good target with almost 6.5L recovered.
From that point, there were 2 other locations for fluid to stay in... the transmission cooler + piping, and the Torque Converter.
So I set out to disconnect the tranmission cooler thermostat that is just in front of the gearbox. This would help me get the oil from both places, as I would have access to the cooler lines, and the oil pump to feed the cooling system is in the torque converter , so I'd be able to think of something to pump it out.
The thermostat can be removed easily to let the lines drain themselves immediately. Afterwards, instead of using some jury rigged plug, I simply used a poly tubing with 5/8 I.D. that I warmed up and was able to easily slip over the cooler return line. Then I used an air gun with a rubber tip that fit the cooler line and SLOWLY pushed air into it and got the lines and cooler to empty.
This is the Harbor Freight air blow gun kit I used. The rubber tip works great and is sized just right.
Again, not a lot of pressure required here and because the piping is long, there's a 'delayed' reaction let's say to the oil building up on the way back and coming out, so be careful!
So now with the cooler+line done, there was an additional 1.5L recovered.
That left the Torque Converter housing. While I dont think it's realistic to expect the torque converter to be emptied completely, there is a pump in the housing (according to ZF's diagram feeding the cooler).
So skipping a head a bit, I reinstalled the pan, filled til the fill hole started to drain. A trick I picked up in the Dodge community... crank the motor 4-5 seconds so the pump can run and catch the old oil. It's important NOT to run the gearbox empty! And at the same time, the fill I did (~3.5Qt) was way less than the capacity of the system.
I monitored the return hose while I had a helper crank the car for a short period of time. I ended up getting less fluid back than I anticipated before seeing the new fluid (more on that later), below the 1L mark,
In this step, just a bit more than 1/2 Liter recovered.
The pump pipe is the hose on the transmission side, closest to the pan
In total, recovered just above 9L in the jug... Accounting for some spills, maybe about 9.25L total. You can see by that Qty recovered that a simple pan drain and refill will not be sufficient to swap out the fluids, unless you go into a painstaking and wasteful multi-drain exercise.
This also means the refill procedure is going to have to be a bit different.
The well documented ZF approach is to fill the pan til the fill hole drips, plug it, then start the car til it warms up, do the procedure, then refill. The pan will only hold ~3-3.5Qt , which means that in this case, filling the gearbox, and cooler will drain it quite quickly.
The thermostat isn't a full bypass, it has a 10% flow to the cooler even when in cold temps so that will contribute to the oil being spread everywhere quickly. So I approached this in a similar way to the Torque Converter drain. I filled the transmission , ran the car for 10 seconds. Shut it down, and filled it again.
I did this 3 times and almost put in almost 8L back total.
This procedure is important as it allows the oil to work its way into all the components, and get warm enough to expand everywhere. That's the procedure to follow, after which the entire fill procedure is complete.
In total, after all was said and done, I used my electrical transfer pump to fill back in 10.2L + about 1/2L waste dripping back out.
More on the discrepancy between total drain and fill volume just below!
#2 The Pan
The Aston Martin 8HP replacement basic "Oil Pan Kit" (the pan has integrated filter) contains OE pan, attachment bolts and fill plug.
The pan is made of plastic.
It is Aston Maritn part # FD33-22700-AA ,
Which is ZF part # 1087.298.364
The ZF piece pan on my car was manufactured by Filtran. Newer version of the same part # are also made by Hengst.
It's also possible to fit the same pan, made for MOPAR, with the "Pentastar" on it to fit our car. There's quite a few OE versions.
In the service part aftermarket, you can find this pan made by Febi Bilstein, Meyle, Vaico etc.. These are OEM shop suppliers and the part is likely identical. Then there are Chinese knockoffs you can find on eBay, but I wouldn't seriously consider them if I were you.
Then there are aftermarket "Performance" parts pan for the 8HP. Most of them look very good, and are cast Aluminum instead of plastic. One of the popular one is PPE, (Pacific Performance Engineering) 8HP aftermarket pan.
Unfortunately, most of these pans have a higher fluid holding capacity, which means they are somewhat thicker, and would not fit under my gearbox due to the undertray shield that's fitted there. So I had a to be conscious of that when looking for what would fit.
In the end, I settled on a very good Aluminum 8HP pan made by "IN Power Developing" in Taiwan. It has out of the box fitment compatibility with Toyota (Supra), BMW, Land Rover, Jaguar, Maserati, etc... and directly compatible with the original ZF pan kit #.
Side by side, you can see it has a similar integrated filter, and the kit comes with mounting hardware, magnetic drain plug, and replacement fill plug (like the OE ZF kit).
More info from the manufacturer of the pan on youtube here:
The pan is SLIGHTLY deeper, which means that it will hold some more fluid than the original, but will still clear the undershield tray on the car when installed. This explains the re-fill fluid I used was different than the drain volume.
It's just a shame once mounted, that it's hidden away like that, because it is a VERY nice looking item worthy of the car.
#3 Fill Fluid
The ZF 8HP on our car comes with ZF LifeGuard fluid.
Overall, I would categorize the fluids for the 8HP in 3 classes:
OEM:
There are actually 3 compatible LifeGuard fluids for the transmission (4 if you have a 6HP as the fluids are backwards compatible):
They are all semi-synthetics made to/by Shell Oil specification M-L12108
ODM, Manufacturer:
These are OEM relabelled version of the SAME oil, approved by ZF in document TE-ML 11:
They are mostly relabelled under manufacturers (Audi, Aston Martin, BMW, Jaguar, Bentley Porsche), but also available under Oil brands (Petronas, Iveco)
If you're price conscious and want to stick with OE fluid, these are often on sale much cheaper than the ZF branded fluid.
Aftermarket:
Here the availability is a bit wild. There are probably close to a 100 products labeled as "Suitable for Use" or outright "Meets ZF criteria". Some of it you can even buy at the local gas station: the 8HP is not a 'unique unicorn' on the market, and given its wide adoption, there are PLENTY of good aftermarket fluids.
The top two on my list were:
#1 Valvoline Max-Life Multi ATF. This fluid is very popular and has an excellent track record. It can be bought at Walmart, for like $20 / 5Qt . I would recommend this oil in a heartbeat. It is red in color.
Also the Valvoline Extended Protection ATF appears to be an even better fully synthetic version. https://www.valvolineglobal.com/en/e...rotection-atf/
HPL Green ATF, Cold Climate. This is the oil I picked and bought during a Black Friday sale special. It is fully synthetic oil.
The regular version uses a Group III synthetic base, and the Cold Climate version I picked uses a higher end PAO base which means it has the same viscosity specs, but a much wider Viscosity Index and low temperature pour point. It's also the same green color.
If you want more info, you can check this link https://www.advlubrication.com/colle...41597446226113 or product data sheet: https://www.hplubricants.com/wp-cont...04/ATF-PDS.pdf
If you want more info or feedback on these oil there is a well known Oil related forum run by Bob that will provide a LOT of info!
The other contenders I looked at: Amsoil , Motul, Liqui-Moly, Redline, Ravenol, Castrol (Transmax) . All of these major brandname products looked VERY good. So there's a lot of choice out there that will meet or exceed ZF's fluid.
A lot of oils are also available from local known brands , Mannol, Mobil-1, Petro-Canada, etc.... There are a LOT of compatible oils and most of them are very good. So shop around!
In Conclusion: Was able to do a comprehensive fluid change of the 8HP gearbox, recover the majority of the fluid (I dont have a clear # of what the whole system holds, but was told 10Qt), upgrade the drain pan and refill with a superior aftermarket product.
Happy to share any more details if anyone wants to ask. I'll likely put up the 6HP/8HP flush tool in the classified section as I wont be using it anymore , if anyone wants it.
Last edited by UltraMarine; Mar 29, 2024 at 05:47 PM.
I've contemplated doing the 8HP in my DB11 V12. I've done a number of 5HP and 6HPs in the last couple of decades (all of which had fill for life specs). On all of these I used the refill process that has the engine running and starting out with cold (room temp) fluid then monitoring the expanding fluid temp to spec while the excess drips out, then capping the fill plug.
I know many use the method of measuring the drain then replacing that same amount.
I am planning on having this service done next season. I'll be over 50K by then. I've had it done on a couple of Jags. One of them because the pan was cracked some how. That one was done at like 25K.
I am planning on having this service done next season. I'll be over 50K by then. I've had it done on a couple of Jags. One of them because the pan was cracked some how. That one was done at like 25K.
The pans are plastic. Wouldn't take much of a bump on something in the street to crack it on a Jag. They weren't covered with a wind tray. I've done a "few" on Jags.
Sorry for the trivial question, but how did you measure the fluid temp during the refill process?
Good question. I used a Thinkdiag2 to stream the temp data to my phone. It supports both 6 & 8HP .
The temp sensor is in the oil gallery of the control module assembly, so it's accurate and what the same reference the shops will use. Do not use a thermometer against the external casing
I took a screenshot while waiting for the temperature to rise.
Last edited by UltraMarine; Mar 30, 2024 at 07:25 AM.
Sorry for the trivial question, but how did you measure the fluid temp during the refill process?
Because you are monitoring the fluid level with the fill port open, and the fluid level is just at the brink of the port lip, fluid temp can be taken directly at this point. Fluid temp, AND NOT CASE TEMP is essential in getting the correct level at the threshold temp of 40*C (for the 5HP and 6HP, not sure if 40 is correct for the 8HP). Some were using an infrared gun and measuring case temp which will give a very incorrect fluid level BC the fluid would be well past 40*C before the case got there.
I modified a digital thermometer with a probe to work directly through the port and into the fluid itself. The whole process of getting to 40*C from cold, with the engine running took about 12 to 15 minutes depending on initial fluid temp cold. Here is the temp gauge I used.
