My XKR has had the shift chirp from the sticking E Clutch since I got it three years ago at 30K. I took it to the dealer for the standard additive repair and they claimed they never heard it, they must need hearing aids! It now has 50K on it and the noise was getting louder and louder, becoming decidedly annoying. I took it in for a tranny oil and filter change and when I got it back, the noise is completely gone and in addition, the shifting is smoother! Although the tranny always shifted nicely, it is butter smooth now. I highly recommend this service, even at the $400 cost it ends up at. I asked the guys at the shop how dirty the oil was and they told me it was very dirty so I was glad I got it done early. I took 6 liters to fill it. I think the current Lifeguard 6 oil from ZF must have a corrected additive in it that fixes the problem.

 

Glad you had it resolved, too bad it took so long. I had my car to the dealership for the chirp noise and told them I wanted the fluid and filter changed regardless (I knew about the additive from this forum, but I never mentioned the additive to the dealer). They replaced the fluid and filter (60k miles) and it still made the noise. They called me to tell me that it would be another day before I got the car back because they "did some research and found out that there is an additive that will resolve this" but, they had to order it. Plus, they said that had to call around to other dealers and had a quart shipped to them because it was no longer available. I don't know if the additive is or is not still available, but I was considering thrying to purchase a quart for when I have to change the fluid again at 120k miles. BTW, I paid DOUBLE for this service compared to what you paid

 

In order to hold costs down, I ordered the kit from CTSC which cost $240. I then took it to my Jag Specialist who charged $150 labor to do the change. I may have erred in not getting the electronics sleeve changed but I thought that since it was not leaking and the last change on my XJ8 costs me $75, I would take a chance.

 

had the same exact experience, the chirp was taken care of by a zf fluid change without any additive needed. They must be sending out the new zf fluid with some sort of additive or perhaps the jaguar fluid that was produced by zf did not have the necessary additives to begin with. I'd say it is a better bet to go with the zf lifeguard instead of the dealer fluid which may not have the corrective additive.

 

It's too bad we have to rely on speculation for this but I think you may be right, the Jaguars have had a lot of chirping out there, the fluid has to be deficient in its original fill.
I never thought much about it since the Jag dealers were charging hilarious prices for the fluid that made it abundantly clear that they did not want the business, so I went to ZF who had fair pricing for the original stuff. ZF makes it clear right on the container that their fluid is the correct stuff for the 6HP26 and anything else is bogus, pretty much to be expected.
The only danger I see in getting the fluid at the dealer is that the dealer could only buy the fluid in 20 liter drums or larger, so if the formula got changed, the chances of getting the new stuff from the dealer is reduced since they don't do many changes there according to the service writers.