My transmission unit recently failed on my 2005 Jaguar XJ Super V8, and I had it changed (Donor car was a Merc S Class from the same year I guess, as they used the same transmission).

I have put around 3000 miles on the car since the transmission change, and while everything seems to be running perfect, I do have a problem when shifting from Park to Drive when I want to leave my house.

Unless I literally jam my foot against the brake pedal, the transmission jerks heavily and produces a LOUD clicking noise when engaging Drive, otherwise, the shift is smooth (again, provided my foot is pressing down exceptionally hard on the brake pedal).

What could be the reasons for this?

  • What RPM is the engine idling at while in park?
    – HandyHowie
    Oct 13, 2021 at 8:49
  • Is it possible that the replacement transmission has an issue? Was it new, rebuilt, or just used?
    – jwh20
    Oct 13, 2021 at 14:00

1 Answer 1


Jaguar will have made their own settings and control points in the transmission and gearbox control ecu.

Unless the box has been recoded to match then you should expect things like this. Jag may even have particular ratios so it may have been a better idea to source a Jag unit. Just because the outer case is the same does not mean the internals are.

  • I understand that, but Im assuming that some sort of damage is being done everytime the jerk happens, like gears grinding... etc (not really familiar with transmission internals). Is this true? Oct 13, 2021 at 8:33
  • 1
    While what you say is likely, I'm not clear how this would cause the symptoms described.
    – jwh20
    Oct 13, 2021 at 14:01

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