www.jec.org.uk

Hi, I have had to suffer from the gearbox lurch since I bought my 2005 s type diesel in 2008 with 35000 miles on the clock.
Many visits to the main dealers did not stop this problem.
It had the software replaced with the latest version, but nothing stopped the lurch from coming back. I have got used to it as the car has now done 90000 miles.

Until I had the gearbox oil and filter replaced and the brakes overhauled by XJ Restorations.
The Lurch has not re appeared since, the car has done 1500 miles since the service and my driving has not changed.
The brakes were in need of a full set of discs and pads, it seems the problem of the gearbox dropping into first gear while still slowing down at junctions etc. is actually due to brake problems not the gearbox.
I hope this may help anyone else with the Xf gearbox that does the same jump/lurch when slowing down.

I think the software for the Abs, when the brakes are below parr upsets the gearbox self learning, causing the problem.
I hope this helps anyone who has the same trouble.
Happy motoring.

Hi Vernon I had the same thing but a gearbox flush/filter and reflash sorted it out. I don't think it was anything to do with you'r braking system.

Jeff

Oil quality, or the lack of it in higher mileage vehicles does seem to make quite a difference to how the ZF six speed units operate in service. There are I believe several difference types of "lurch"which can develop with seemingly different situations where that issue crops up. www.the lurch.com is the site where much discussion takes place on the matter.

Seemingly the most popular form of lurch is a very hard downward shift from second to first gear in slow traffic. Many owners so affected have remarked that the effect is as if the car gets rear ended.

If not already visited, the above site might shed further light on the issue. Similar transmissions are also to be found in other highly popular German vehicles so take some heart that it is not Jaguar models that are affected.

Mike

I have visited the lurch.com and have gathered all the info available, including Jaguars own workarounds for this problem.
The car had only done 30,000miles when I purchased it and the lurch was there from the start.
Not only does it lurch when slowing drop into first, it also speed up the car. If it was just the gearbox going into first gear it would just slow with a jolt, but it jumps forward, requiring more brake pressure to avoid the car jumping forward to far.
That's why I think the Abs, gearbox and engine management processers are all involved with this problem.
Still it's stopped now so all good.

For what it's worth.
My STR had a similar problem with low speed shifts. Often feeling like a gear was not selected and suddenly making a decision. (lurch ?)

The car has covered some 85K so I decided to have the transmission serviced, new oil, filters etc. Not a cheap job at circa £300.00 but oh what a difference. Just drives so much better.

Recommend it

Hi all, I have the same problem I have had the gearbox oil changed but it still some times lurches, i think the next step like you say is to have a reflash. Fingers crossed this might sort out the problem.

Did the garage just change the oil alone without reflashing the software by cycling the gearbox with a laptop to obtain the correct operating parameters? This is part of a "proper job" procedure after changing oil.

Mike K