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Transmission swap


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Hi all 🙂 been a few thousand happy S-Type miles since I last posted, but i've run into a few issues with the 6HP26 auto box - repeatedly getting ratio errors and 5th Gear ratio incorrect - making some nasty noises on hard kickdown too before shuddering and locking into 2nd with "Gearbox Fault" on the Info display.

I've sourced the correct grade of gearbox oil (Thanks to Smith & Allen - excellent products, price and service 😄 ) and a filter set to see if a fluid change sorts the issue, but as part of planning for something more serious, I've been looking at more drastic measures. I've found a local breaker who have a 6HP26 box from another 3 litre 'S with low miles on the shelf for a quite reasonable price, so I'd like to ask of those with more knowledge - are transmission swaps a simple matter of physical exchange ? or will I run into issues with the TCU spitting it's dummy at a "foreign" gearbox wired up to it ?

Any advice ?


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Yes unfortuanately, the TCM on the 6HP26, is built into the gearbox

so swapping the gearbox, will cause loads of problems and the car will not even start

the gearbox tcm is networked and talks to most of the modules on the car

it would need programing to the car with something like Jaguar IDS/SDD

lots of jaguar indy's have it and should be able to program it, problem is once you swap the box your stuck, wont drive or start

Serviced my gearbox a few years ago and only used genuines part and oil, ZF lieguard 6, lots of people use cheaper oil and end up with a host of problems after

usually the main problem is the mechatronics, which is the valve body in the bottom of the gearbox, this has the tcm built in, you can get service kit which will cure most faults, like a sonnax kit, which replaces all the little pistons and valves in the body , also a set of solenoids whichs controls all the gear selections and clutches, is usually replaced which comes seperate.

also if the software is the original build that can cause problems, updates can cure a few issues like banging gears and surging when cold, a adaptation reset will also be required, this clears all the learnt data the gearbox learns and helps the gearbox to drive smooth again



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Comprehensive reply - many thanks 🙂


I'll start with a flush, oil and filter and see where that gets me. My fluid is dark, but doesn't look or smell burnt so hopefully ill have some luck !

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