E270cdi 722.6 Strange one!! target & actual gear Implausible

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New Member
Jul 21, 2022
milton keynes
Hey guys

I've got a nice 270 cdi that might have the wrong box in it.

Trouble is it's so hard to read off the little flat area where the actual gearbox spec is stamped, I know it should be a 722.640.

I've changed the conductor plate and checked plug/wiring/tcm and fitted a couple of spare known good solenoids all to no avail. (only fitted solenoids as I was there I knew they wouldn't cure it)

Start off creeping forward all is well...it's in 1st gear but much above a creep and live data for target and actual gear immediately display implausible (Autel scanner) at which point the car shifts up to what I think is 3rd and thats it.

Switch off and on again and until you move much more than creeping it is ok again. It cant be slipping because you dont have to move enough to generate any slip - it's literally like the speed readings are wrong - it is getting readings from everywhere - wheel speed, engine, conductor plate etc but something is off and appears to be triggering limp.

All speeds inside seem to be reading as they should, I know that N2 and N3 dont always read the same depending what gear you're in but they match when they should (in 3rd) and for the brief moment you get to drive in 1st you get no reading from N3 which I believe is correct.

My question is could the gearbox be say one from a 220 and so the internal ratios are wrong ? Or a 320 for that matter...

Checked the diff and it's the correct 2.64 the car left the factory with.

Just looking for any help before I replace the trans.

Oh also it had another TCM floating around behind the footwell panel so someone has obv been trying to solve this issue in the past. What I assume to be the car's original TCM was also there, neither of them make any difference.
I have come across a broken toothed ring inside the transmission, if you remove the valve body and look through the holes in the trans casing (above where the speed sensor on the plate is) you can rotate the cage and check for cracks??

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