Tranny fluid flush vs fluid change
 

Would like the collectives thoughts on a transmission flush vs a regular drop the pan and dump type change. I have 134000 miles on my 2005 XJ8L, bought it at 114000 a year ago and not sure of history. Running good.

In my opinion it would be far better to do a complete flush with that high mileage.

Far better to do a complete flush anyway no matter what mileage.

I agree with John, a flush is the way to go unless you have other issues like a leaking pan or mechatronic sleeve where a pan drop would be necessary anyways. While changing the filter/magnets is not a bad idea, I have not seen a lot of evidence they need changed if the fluid is changed at regular intervals and there are no other issues with the transmission.

Here is a recent thread in the x100 forum on the same topic that you could reap some varying opinions on from the topic:

https://www.jaguarforums.com/forum/x...-both-196866/L

Hi JaguarXJ8L2005,

Since both Jaguar and ZF (the transmission manufacturer) claimed the transmission was "Sealed for Life" when your car was new, it is unlikely the transmission fluid has ever been changed. ZF subsequently changed its recommendation to state that, "Depending on the driving style, ZF therefore recommends a transmission oil change every 80000 to 120000 km (50,000 to 75,000 miles), or after 8 years at the latest."

Since draining and dropping the pan leaves a significant amount of old oil in the torque converter and other sections of the transmission, a true flush is really important. The filter is built into the pan, so the pan must be replaced, and many owners have discovered that some of the pan screws will break during removal, so it's prudent to have at least a handful of new screws (if not a full set) when you do the job.

A sequence that seems to require the least amount of new fluid is to flush the fluid via the cooler lines until only fresh, new fluid is expelled. If I recall correctly, this will take 10-12 quarts. Examine the old fluid for any significant presence of metal or friction material particles.

Now, remove the drain plug and capture the (new) fluid in a clean catch pan for re-use. Drop the transmission oil pan, clean the gasket surface, and install the new pan. Replace the electrical connector plastic sleeve. Refill the transmission with the fluid you captured and set the fluid level per the Jaguar Workshop Manual or ZF manual instructions.

Use only ZF Lifeguard 6 or (Ford) Motorcraft Mercon SP fluid. Members of this forum have spent countless hours researching this issue, and these are the only two fluids proven to be correct for the ZF 6HP26 transmission. In North America, Mercon SP is typically significantly less expensive than LG6.

Cheers,

Don