transmission fluid theory?
 

What is the theory behind sealing the transmission fluid within its case forever and never changing it. There is no drain plug, right? So I assume that the engineers behind this change must have come to the conclusion that fluid changes are unnecessary and perhaps even harmful. How long do they think the car should be able to go with its original fluid, i.e., do they see a 'life' to the transmission or if one could get a million kilometres out of the engine and drivetrain, the transmission fluid would still function successfully?

Life of the warranty period, not life of the transmission, but I always change my filter and fluid every 60k. But caution if you are well over 100k and fluid is black and dirty. You can well find that you put new fluid in and then no longer shifts correctly and slips. And thats a drain and fill, I do not recommend a flush.

Bill has given the official and accurate answer.

For those of us who can recall when our new XJ Jaguars used to dissolve into a pile of rust in less than five years, transmissions ALWAYS exceeded the lifetime of the vehicle.:icon_lol:

Graham

Hmmmm. So Jaguar Heaven should be full of functioning sealed transmissions buried under tons of rust. Not sure if my S type has ever had its fluid and filter changed and its over 180 000 km right now. I expect it was changed while under warranty at least. No way of checking it.

I guess the theory was [and is?] that the missing drain plug would force owners to change the filter on a regular basis and that would preserve the transmission.

Iirc that trans is a ford unit and it should have a drain plug

I am nearly sure it would not have been due a change under warranty!

As Brutal says, it is a Ford unit - 5R55N - and has such as a drain plug. Cheap fluid.

BTW better to post in the S-Type forum :) and also there are many posts about that box already, with full details.