Any advice would be welcome, When cruising along at about 40 I sometimes get a speed variation slow fast slow fast at about the rate that you would say the words.
Everything else seems ok.

 

Thommo,

I've moved your question from Jaguar Forums Advice / Feedback & Suggestion Center to S-Type forum. The Advice / Feedback & Suggestion Center is for posts about the forum and not for technical questions.

Members here with the same model will be able to help.

Graham

 

Could be the TC (torque converter) failing to lock up. Lots of posts and a TSB about it if you have a look around. (But I thought it was a rev change rather than actual speed change.)

 

Thanks Jag v8, would an oilchange in the auto box help that problem? I also notice a slight growl in time with the variation when this happens. It only seems to happen between 1500 and 2000 revs which may be when the torque converter is locking and unlocking.

 

Unless it's low on fluid - see stickies for the vital way to check - then I don't see how that would help.

 

So it's engine speed and not vehicle speed that fluctuates. As JagV8 stated there's lots of discussion here on the subject and a factory TSB involving a reflash that may fix it.

A fluid change will do nothing.