Well, since opinions are like you-know-what, and everybody has one.......here goes.

I'll stick with the 'Filled for Life', mostly because, as you have yourself noted, the ZF fluid is an extremely high quality fluid. Today's fluids just do not break down and oxidize as fluids in the past.

Second, and I have mentioned this before elsewhere, a ZF technical fellow once made a case that I have yet to find a way to dispute. Transmissions operate with clutch packs that are stacks of alternating steel and friction disks or plates. Hydraulic pressure presses them together to hold various gears, and allows minor slippage during gear changes. Obviously friction plates wear over time, and this shed material goes into the fluid. His contention is that this material, suspended in the fluid continually circulates with the fluid and keeps coming back the the party and plays a roll in the friction packs. These are fully adaptable transmissions that adapt to the friction properties [or the changes in friction properties] over time. By flushing and exchanging the fluid, you in essence flush out a good bit of 'friction modifier', his words, right out in one fell swoop. This causes and immediate change in friction property within the transmission. He said,"Ever heard of a trans inexplicably acting strange after a fluid change?" Made me ponder......I've lived by that ever since.

To the point of the dealer's 'change of heart'? I'm thinkin' a vendor has come through and sold them on a new revenue source. [I hope my boss doesn't see this] More than likely that vendor also wants to supply that "compatible" fluid.

Just my opinion, and not necessarily that of the management.

Cheers,

 

Thank you for your valuable input!

Isn't viscosity change a concern, even with an adaptable transmission? At what point would you change the fluid? I got the impression after real world experience they decided to advocate the need for fluid changes under some conditions.

And while we are talking about fluids, what do you think about the rear ends being sealed for life?

In my industry our engineers always discover a change in longevity when shifting from controlled environment lab testing to the real world where the variables are much greater than accelerated environmental testing.

 

My wife's VDP has the "whoop" sound on the upshift and downshift. After reading the info on the forum and talking to my local mechanic who knows Jags inside and out, he is of the same mind as xjrguy. He said he talked to his ZF guy and they had not heard of the info saying that "spirited drivers" should change the fluid at ~60K miles. His feedback was the fluid lasts for well past 100K miles in his experience.

Someone on the board is selling me an unopened bottle of the additive and I am gonna have him put it in. He was *completely* against changing the fluid out provided there was no other mechanical issue going on.

TIFWIW...

 

Always nice to have an appreciative audience, thanks!

Well the viscosity change idea speaks directly to the stability of the fluid, which we've agreed is very good in this case. Since you mentioned the 'controlled environment', think of it this way; these units, trans or differential, are basically sealed units, a controlled environment. About the only things that can happen are:

A leak and fluid gets out
Vent caps or tubes get damaged or broken off [giving access to contaminants]
Something breaks, an outright failure [We'll include abuse here]
**This is rare these days, with the exception of the 5HP drum failure
The fluid gets contaminated, say the car gets underwater for instance.

Metallurgy, fluids, manufacturing methods are all so much better today, that unless the things listed above occur, the fluid will outlast the unit for the most part. Certainly long enough that I'm not gonna waste any worry on it.

Used to I would consider maybe changing trans fluid if there was a serious overheat and the car was not shut down in a short time; but with these synthetics, I don't worry about that very much.

Just remember this is all opinion. Someone else will tell you I'm full of it.


Cheers,

 

Only way to realy know the condition of your oil is to do an oil analysis. Have done this on my MB box a while back, and it was needed after about 70Kmiles. Mercedes also came back on their filled for life policy, and advices now 40K intervals even. Not implying these boxes are the same, but also ZF recommends to change the oil between 50K and 70K milespendign on usage.

ZF 5-, 6- and 8-speed as well as the ZF 4HP20 automatic transmissions are filled maintenance-free with specially developed partially synthetic ATF oils. Maintenance-free fills are intended for normal operating conditions. Especially driving at very high operating temperatures can result in accelerated aging or increased wear of ATF oils. It is recommended, in the event of severe operating conditions, such as:
- frequent highway driving in top speed range,
- offensive, sporty driving style,
- frequent trailer operation,
being above average, oil purification (oil change) on automatic transmissions is recommended between 80,000 km and 120,000 km, or 8 years, depending on the load. In each case, only released ATF oil may be used for oil changes. And oil changes must be performed in accordance with the relevant specifications.

 

"- offensive, sporty driving style,"

That would be every other driver found on the road

 

Hi guys,

I am new to Jaguars (am looking to buy an XJ8 this summer) but I do know about transmissions and fluids, so I'll chime in here. The ZF transmission used in these cars is purchased as I think you know and it is ZF that does the design and manufacturing, not Ford/Jaguar. I can tell you that the fluid designed for the ZF transmission is not at all specific to Jaguar, although it will be supplied in Jaguar branded bottles. It is specific to the transmission design. Any vehicle this transmission is used in will absolutely use the same fluid, afaik.

Now, there are several important things to understand about ATFs. This is the most challenging automotive fluid application of all for several reasons, but a big one is the service life. Engine oils get changed every 5 to 15k mi, but not ATFs. So, the components that make up the ATF experience a longer life cycle and have to be more durable (for lack of a better simple term). There are components in the fluid that protect the metal parts from wear, components that disperse oxidized materials, components that control friction, components that control viscosity, etc etc.

Now the friction profile is very significant - it _will_ affect your shift quality, no matter the age of the fluid or transmission. Barring mechanical changes through wear to your transmission, you will want to stick to the manufacturers fluid - for ANY transmission. The friction profiles are absolutely designed to meet the manufacturers specifications - not only for performance and lifetime but critically for "shift feel" and the torque requirements of the transmission. Using a different fluid - particularly any fluid that says it is good for any transmission - is asking not only for long term trouble but also you will experience different feel.

For example, probably the best transmission fluid in the world today is Dexron VI in GM products - but you cant use this fluid, for example, in a Daimler. It is just different - I could explain but its technical. What you would notice is a different shift feel. In some cases you would experience degraded durability in the long run.

Finally, changing your ATF. There are components - the smelly ones that contain sulfur, that get used up over time - they are doing their job, but they get used. There should be enough in the fluid for 100k plus miles, but it will never hurt to swap out that fluid - with the same fluid. Using a different manufacturer's fluid is not a great idea - you dont know what to expect out of it.

I would suggest you change it as often as you need to for piece of mind - but absolutely stick with the manufacturer's fluid only - they have designed and tested around this fluid and you should use it.

Hope this helps.

 

Oh, I forgot to add: For the most part, synthetic/non-synthetic really makes very little difference these days - the non-synthetic fluids are based on more refined oils that are just as durable, but still different, from the synthetic oils. Another term you will begin to hear is GTL - gas to liquid - and these are another variant. Performance differences among these high quality base oils will be minimal (but slightly different) and you shouldn't generally worry about them. If you use cheap or old-specifications (such as Mercon 3 or Dex3, for example) then the synthetics and gtl will be improved, but mostly these fluids will have replacement, modern formulations to use instead.

There will be specific situations where this generalization will not be correct but for modern fluids, basically this is the situation.

Use the manufacturer recommended ATF =)

 

Welcome to the forum!

So is that without a doubt confirmation that Mercon SP Ford specifies for their ZF 6HP26 transmission at $5 per quart is the same as the Jaguar Lifeguard 6 at around $60 per quart? Unfortunately there seems to be a great deal of mystery around this.

 

I don't know that for sure, but I would be surprised if they weren't the same. It is possible that the Jaguar fluid was reformulated to meet different shift feel requirements. I wouldnt say without a doubt, but its a guess.

 

Only a petro chemist with access to the files can tell us what the fluid differences really are. The rest of us are relagated to following the manufacturers recommendations. ZF recommends doing a drain and refill on the 6HP26 at 60K miles. They do this in their rebuild website, not their main website, so it is hidden from normal view. I have done this on my two 4.2's and can tell you that it makes a noticeable difference in driveability. The trannys in both cars had developed some bad habits by 50k such as lurching after a stop, rough 1-2 shift at start up, loud chirping from a sticking E clutch at the 3-4 shift on hard acceleration and shifting that is not as somooth as it should be in all gears. After the fluid/flter change with the Lifeguard6, all this behavior stopped, not just some, but ALL. For the cost of about $500 each at the experienced indie, it was money well spent for me. My guess is that the friction modifiers in the fluid lost their effectiveness and needed to be replaced...simple as that.

 

I should have mentioned that the fluid in the XKR was black at 50K, the XJ8 was not quite as bad. Since it starts out basically colorless, this is an indicator that the fluid is contaminated. I also replaced the Motronics sleeves in both units at the same time to preclude the usual 60K leak that can start there.

 

Wow Jahummer - Mercon SP is 5$/quart compared with 17 for the ZF fluid.
I dont have the date sheet anymore since the SP was 15$/quart at the ford dealer at the time I was looking for fluid and the ZF could just be ordered online, but I compared the SP data sheet with the ZF and it is exactly the same fluid - I remember clearly.

 

Of course this only covers the physical and Chem. properties as viscosity, pour point, flash point etc. but all this was a match - obviously the basic chem. composition could be different, it did not mention that - I doubt it though. When I had my sleeve replaced I brought the ZF fluid to my dealer (since I did not want to pay 30/quart) and dealer made a point that the zf lifeguard6 I had brought was the right fluid for the transmission.

 

Just had the transmission serviced for the first time at 88k (just took ownership not too long ago) using the liquid gold zf Lifegaurd 6.

The small clunk noise that sounded like drivetrain lash when starting from a dead stop is gone. It also seems to shift a bit quicker, with less effort. Obviously this is qualitative data, but I'm confident there is an improvement. I will likely do a drain and fill (no pan) in another 20k miles to get more fresh fluid in there, then go back to every 60k as scheduled.

IOW, even if you didn't do it when ZF recommends, do it!

 

I'm using Mercon SP on mine XJR and i'm using it on customers cars - no problems at all, transmissions works flawlessly.

 

A little over a year ago my wife's '04 XJ8 started shifting rough on the 1-2 upshift and 2-1 downshift sometimes prompting the 'gearbox fault' alert. With more than 150,000 miles the car isn't worth having a transmission overhaul so I tried changing the fluid. I read all the ZF, Jaguar, BMW and other manufacturers BS propaganda about only using the insanely expensive ZF Lifeguard fluid so I did a little more research and found some Ford Motorcraft SP fluid recommended only for ZF equipped Lincoln Navigators and changed the fluid and pan/filter assembly with good results. The transmission still shifts rough at times but for the most part the problem is solved. Although the car is still in pristine condition it's worthless on the used car market so it was worth experimenting with a "non-approved" product. Furthermore since the car's warranty expired, it has only been at a Jag dealership one time and that was for the replacement of the air suspension compressor. I found a shop manual on ebay and I've done all the maintenance myself. I've since bought my wife a new C class Mercedes so I guess I'll drive it until it quits and then I'll sell it to a salvage yard.

 

I have just got my new pan kit, bolts, sleeve and Lifeguard 6 ready for the changeover

I know many others say Mercon SP is ok but Lifeguard 6 is now readily available and reasonably cheep.

Just my 2 cents but for me I see no reason not to use the genuine Lifeguard 6

Cheers
34by151

 

Way to go Kratzerap. You did the exact right thing. This proprietary Lifeguard fluid for ZF products is simply a marketing ploy to sell high priced stuff. No disputing that Lifeguard is a good product but several other products work just as well at a lot less cost. I ran Mobile 1 in my XJR with excellent results.


Let the purest games begin.

 

As long as you actually change it and disregard the sealed for life nonsense, all is well, from a purist standpoint ;-)