A4LD torque converter lockup in top

[ajlelectronics]

Can anyone provide a truth table for the operation of TC lockup in third and fourth please? My recently acquired Scimitar GTC 2.8 has an A4LD and because it isn't being run by an ECU, there is no lockup in top. I can design a suitable interface, but I need to know under what conditions should it lock and drop out again? I phoned the specialists who screwed me for £426 to repair another one, but "Dunno guv" was the response.

Also the shifter has been bodged. Instead of the Granada staggered gate shifter, an original C3 shifter has been used, with the detents ground away to allow fourth to select. If anyone has an early Mk 3 lying about, I would be interested. (with shroud).

 

[Wallace]

Don't know about the A4LD but I have an A518 4 speed lockup installation that uses a couple of pressure switches and a vacuum switch to bypass all the original electronics. PATC do a lot of this type of conversion in the States link here to their A4LD page and here for a pressure switch conversion if it's any use to you.

 

[ajlelectronics]

Thanks. That article suggests it is purely down to road speed. I was under the impression that there was a vacuum sense too though, hence my question. My guess would be that lockup at speed would drop out or be prevented with low manifold vacuum as in accelerating.

 

[Wallace]

I have a vague memory of vacuum loss causing gearbox problems on Granada's, but don't quote me on that. On the A518 conversion the vacuum switch is used to sense a light throttle cruise condition and a pair of pressure switches (44psi & 52psi) then allow the 4th gear then lockup solenoids to engage as in the diagram below.

 

[colnerov]

Hi, I will admit that I'm not up to speed with modern electronic 'boxes. I thought that changes and lock up were controlled mechanically, in the last case by the governor on the tailshaft. Kicking it down usually selected 3rd and so lock up dropped out because it only did that in top. The electric side of it only controlling the shift quality i.e. comfort or sport, or tiptronic if fitted. It now seems that 'boxes are fully computer controlled.

The point of all this pre-amble is I did a bit of research and this 'box is not fully computerised but just a transitional one (for the want of a better word). I came across this fault diagnosis, which suggests that it is just a case of wiring a simple switch to prompt lock up or adding in a simple speed sensor to control it. -

http://www.justanswer.com/ford/18q2z-a4ld-transmission-doesnt-always-work-correctly-when.html

Hope this helps.

Colin