Auto gearbox shift lock not working

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Med_tech3
Posts: 58
Joined: 01 Nov 2018, 12:18
x 1

Auto gearbox shift lock not working

Post by Med_tech3 »

I have just had a new gearbox fitted under warranty to my 2008 c3 automatic. It now judders before engaging when first put into drive after turning on the ignition. Also the shift lock doesn't work so you can move the lever from park to reverse, neutral or drive with the engine on and not touching the brake pedal! Do you know what the garage have missed/done to cause the failure of the shift lock and is a slight judder when first engaging drive normal?

Thanks
Simon
ozvtr
Posts: 97
Joined: 13 Oct 2020, 01:11
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Re: Auto gearbox shift lock not working

Post by ozvtr »

WOW, there are a lot of things that they could have done wrong!
Is it a new gearbox, reconditioned or from a breakers?
If it's brand new (doubtful but...) there shouldn't be a problem with the 'box itself. Maybe the alignment of things (see below).
If it's not brand new all bets are off! Even if it's reconditioned they could have made a mistake in rebuilding it.
Could be bad alignment of the Bowden cable from the selector in the cabin to the gearbox.
Bad alignment of the selector switch on the 'box (although this is typically associated with the gear indicator on the cluster flashing).
Bad alignment of the manual valve in the valve body and the selector detent quadrant in the gearbox. The leaf spring not adjusted correctly?
Bad/missing ground. The battery ground should go from the negative terminal to the gearbox then to the chassis. Those connections are under the battery box. Should be tight.
Bad electro valve(s) in the valve body.
Physical damage in the gearbox (break band(s), maybe).

The shift lock solenoid might be stuck. The amount of coffee I have seen spilt into the shifters is about the size of the GDP of Brazil! Although, the solenoid is tucked away and a bit more protected.
The brake switch might be faulty. The secondary contacts can give random signals to the gearbox ECU and the ECU thinks you have your foot on the brake.
Again, the shift lock might be tied into a potential poor alignment of the position switch on the gearbox and the gearbox doesn't think it's in park.
civvie
Donor 2020
Posts: 253
Joined: 27 Feb 2002, 00:49
x 8

Re: Auto gearbox shift lock not working

Post by civvie »

sounds to me the garage is some kind of mickey mouse outfit, don't these places check their work before handing back to customers. Was t a back street trader/garage.