1992 V6sei auto gearbox repair

[MTXM]

This may or may not be significant, but I have noticed that the engine revs very slightly increase when gears are engaged and there is much less resistance when moving the selector handle. Regards, Matthew T.

[xantia_v6]

This may or may not be significant, but I have noticed that the engine revs very slightly increase when gears are engaged and there is much less resistance when moving the selector handle. Regards, Matthew T.

I guess that could indicate that something is releasing all of the hydraulic pressure, except in Neutral?

[MTXM]

It certainly feels like there is no pressure Mike, with no gears engaging and very little resistance when moving the lever, but what might be the cause? I understand failure of the pump is unlikely due to the robust design and there would be resultant overheating with discolored and smelly oil, plus probably metal debris. A blown seal or some other kind of leak would be more probable I guess, although where else in the box do such critical seals reside and are there many possible suspects? With regards, Matthew T.

[Dean]

Each clutch has a hydraulic piston that engages it, these have seals.

The detent you feel in the gear selector is from within the box, you can see the mechanism underneath the valve block when removed, it operates one valve which is not spring loaded and offers no resistance at all.
You can feel the detents cant you, i take it the selector cable has not snapped or become detached.

D

[White Exec]

Don't (autobox) engine revs increase slightly when a gear is engaged, to counteract t/c drag, and maintain a smooth idle speed?

[MTXM]

Hi Dean,
I note that each of the five clutches has a hydraulic piston with seals that presumably can sometimes fail, although my fault is effecting all gears. As the engine revs are slightly increasing when gears are engaged I am guessing that the selector cable and mechanism are operating, but I will certainly check when I next remove the valve block. The gear positions feel positive when I move the lever and there is just less resistance I guess as the drive does not engage.
With regards,
Matthew T.

[MTXM]

I believe you are correct Chris that the slight increase in engine revs is normal, which on reflection may be purely down to a message from the switch on the outside of the gearbox. Perhaps I am therefore wrong in assuming the mechanism inside the box is operating, although there is some resistance and the switch certainly works as the dashboard indicator reads correctly. With regards, Matthew T.

[xantia_v6]

Check the diagrams, but I don't think that the neutral switch connects to anything other than the starter relay, so can have no effect on the idle speed.

Maybe you should invest in a pressure gauge?

[White Exec]

Or just injection ECU looking after idle speed? Otherwise, engaging gear/drive would cause idle speed to drop, surely?

[MTXM]

I think you may be right about the gearbox switch not sending information to the engine ecu Mike, but what else would increase the revs when gears are selected? I also agree with Chris that engagement of gears should really lower revs as the engine takes up load, although there is of course no engagement in this case! With regards, Matthew T.