AL4 Autobox Torque Limiting

[jonsowman]

Hi all,

Friend has a problem with his 2003 406 HDi 110 Exec Saloon with the AL4 autobox. Keeps going into torque limiting mode (sticks in 2nd gear and limits acceleration).

Just had it on Planet:
Intermittent Fault: Fault in pressure regulation
Intermittent Fault: Slip: Clutch/brake

Any ideas where to start?

Cheers

[madmadmax]

to start with check the gear box oil and level

after that strip it down and look for the fault

edit: there's a good mechanic near you called krisb

[lozz]

+1

change the fluid, clear the codes
and see what happens,

Make sure you use the correct type of oil jon,

[madmadmax]

thinking about it sum and you may have a hydraulic actuator fault as the slip in brake/clutch may be a brake band ether being warn out or not griping

[jonsowman]

Cheers guys. Update:

Just been out for a drive, when it happened the guide pressure in Planet zoomed to 21.0 bar and the "Pressure regulation fault" was flagged. The actual pressure was nowhere near this, in the 3.0 - 11.0 bar range.

Under normal operation the guide pressure is around the 3.0 - 11.0 bar range and the actual pressure follows it very closely, the modulating valve percentage changing to keep this happening (percentage falling to increase pressure).

When the fault occurs the percentage falls to 0%, as if trying to actually reach 21.0 bar, which is clearly silly.

The "Slip" fault did not reoccur, so we can ignore that for now

The car has been to an autobox specialist recently and has had the oil changed, as well as the "valve block" changed (not entirely sure what this is). Going to get hold of the receipts to see what oil was used - does anyone know what it's meant to be? ServiceBox says "Esso ATF 4HP20/AL4".

[madmadmax]

Esso LT 71141 has become Mobil LT 71141 which is what should be fitted not many people do use it tho.

there are not many thing that that fault description could be check continuity in wires, have you cheeked oil level and color should be green if its red then bin the oil and the box.

the valve block is the electrovalves that put the transmission brake bands on

edit
i was wrong on the brake bands its a multy plate clutch system

have a look at this http://www.frenchcarforum.co.uk/forum/v ... 74&start=0

[lozz]

auto 406.png