I am wondering if a transmission flush is necessary after 34000 miles? More importantly is there a better choice than Jag suggested fluid?

 

No transmission flush necessary or even possible. Just found out about this myself on our 07. Took it in for new fluids and flushes and they told me the transmission and the differential are non-serviceable areas. Who knew!

 

Are you sure about the differential? After the 40K service on my 07 XK the service advisor handed me a list of recommendations. One was for differential oil change. It was late in the afternoon, I wanted to beat the traffic and I'm an hour drive from the dealer. I got a second opinion from a closer eurocar specialist who (supposedly?) replaced the blackened differential oil he showed me with synthetic oil. (One has to wonder if Jaguar used a non-synthetic ?Castrol? differential oil when the car was new for it to oxidize as it apparently did.) OK, at 45K after an oil change and alignment, the service advisor handed me a list of recommendations that included a differential service. When I questioned the necessity I was informed that the tech had not actually checked the diff. oil and that the recommendation was based on the car's mileage. If there's no differential service I've been ripped-off. If there is, you might want to correct a misunderstanding.
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It appears that the transmission and differential are not serviceable.

See this link for the 2007 model year maintenance schedule:
TOPIx - JJM 18 11 99 701 USA - PASSPORT TO SERVICE - USA 07MY

 

With all due respect, although not listed in the required service schedule, one begs to differ regarding the serviceability of the differential - until corrected by a tech type. It has a screw plug.

There's probably extensive transmission information here on jaguarforums.com. However, if'n you'd visit the www.jcna.com/forums xk8-xkr forum you'll find a thread titled "Transmission Fluid and Filter Change" that addresses the ZF six speed auto transmission's fluid. I tried a link from this post to the specific thread but it didn't work.

About the ZF 6HP26 transmission > http://en.wikipedia.org/wiki/ZF_6HP26_transmission