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Following on from this thread: http://www.jaguarforum.co.uk/f32/lumpy-gear-change-low-speeds-36740.html I've finally had the gearbox on my 2003 Super V8 'flashed'. There's some improvement, but that ZF thump is still there - apparently a well-known problem, not just on Jags.

More interestingly, the diagnostics from the initialisation drive they do to 'bed in' the new software showed the torque was out of range on gear changes - about 50% over the limit. If it's letting more oomph through than the clutches are expecting, that would cause the bump, wouldn't it? So - torque converter, not gearbox?

My wallet hopes so.

Also, I do get that 'hunting' behaviour at about 30mph; another pointer to the converter.

The next logical step seems to be to get a transmission specialist to check it out. Can anyone recommend one? I live near Exeter and I'm really hoping to avoid long trips on top of the cost of the repair...

(If anyone has other suggestions as to the cause I'm still open to ideas!)
 

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I cant recommend a specialist near to you, but I have gone along the same route as you with the gearbox reflash. This made things a bit better, but the fluctuating revs problem was still there. As my RAC warranty was coming to an end, I decided to see if the torque converter was covered. Luckily, it was and Suffolk Automatic Transmissions picked the car up on the Tuesday afternoon and returned it to me on the Thursday morning complete with a new torque converter, filter and fluid at no cost to me, but £725 cost to the warranty company.

The car is now totally different to drive. The fluctuating revs problem has gone and the gear changes are smoother. Well worth doing.
 
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