Thread: XYZ switch

Originally Posted by lewy

perhaps a dum question but what does the XYZ switch do.I know the electrical parts talks to the computer but what about the mechanical part [spline into the gearbox]is its only job to engage the park mechanically and the gear selection is left to the electrical side.why i ask this is can the electrical side be bypassed and switches put inside the cab somewere.

It acts as an inhibitor switch, ie. if the 'box isn't in Park or Neutral it won't let the car start, as well as telling the electronic box of tricks exactly what gear + park and neutral has been mechanically selected.

Originally Posted by rick130

It acts as an inhibitor switch, ie. if the 'box isn't in Park or Neutral it won't let the car start, as well as telling the electronic box of tricks exactly what gear + park and neutral has been mechanically selected.

So the functions D,R 1,2,3 of the XYZ switch could be moved to say a rotary switch inside the cab,but the cable is needed to put the box in park which is a mechanical process.

Originally Posted by lewy

So the functions D,R 1,2,3 of the XYZ switch could be moved to say a rotary switch inside the cab,but the cable is needed to put the box in park which is a mechanical process.

The cable selects all of the gears and the XYZ needs to reflect that for the starting inhibitor, transmission computer control and the dash read out. I suspect if you substituted the XYZ for a switch in the dash you would just end up throwing loads of faults.

Why would you do that? It wouldn't end up being full electronic control like the ZF 8HP by doing that.

It's also a fair bet that such a modification could render the vehicle unroadworthy, with consequent impact on insurance etc.

You already have such a switch in the cab, cleverly disguised as a gear stick.

The electrical side of it can be emulated hence the compushift thing: Compushift – Ashcroft Transmissions

Originally Posted by lewy

perhaps a dum question but what does the XYZ switch do.I know the electrical parts talks to the computer but what about the mechanical part [spline into the gearbox]is its only job to engage the park mechanically and the gear selection is left to the electrical side.why i ask this is can the electrical side be bypassed and switches put inside the cab somewere.

The XYZ switch combines the function of the old school neutral safety switch that is in hydraulic shifting boxes as well as the function of signalling to the Transmission Control Unit (the separate auto trans electronic control unit) and I think the engine ECU (too lazy to check the circuit diagrams) what position the auto trans lever is in (ie P R N D 3 2 1)

The 'spline into the gearbox' as you refer to it also moves a piston and re routes fluid in the valve body , so what you are driving at, which is to do away with the mechanical shifter and use electronic control in the cab to change gear selection, will work better by using a servo motor of some sort or a linear actuator to still move the 'spline going into the gearbox' while having a rotary switch or other electronic setup in the cab which controls the servo motor/ linear actuator but leaving the XYZ switch where it is.

A Compushift replaces the factory transmission control unit, but still needs the XYZ switch or an equivalent (ashcroft has a replacement for the xyz switch that works with the compushift) to tell it what position the "spline" is in (ie P R N D 3 2 1)

Can I guess you mean 'I want to get rid of the shifter and look cool with a rotary or push button selector how do I do it'

'I want to get rid of the shifter and look cool with a rotary or push button selector how do I do it'

That's it you have caught me out,i am 68, short, fat, bald, I want to look cool again.or perhaps i don't want to get under the disco ever again to change that bloody xyz as here in Darwin anything electrical simply don't last in the Humidity or the 1200mm of rain we drive through every year.but thanks for the reply it has made it pretty clear as to how it works,might look at the ashcroft offering.