2001 C5 3.0 V6 auto box into 2003 C5 3.0 V6

[Wings]

Thanks for the advice Simon, I have now completed two oil changes with some improvement, not going to do any more. I am preparing to change the box over the next few thousand miles. Can any body recommend a good gearbox overhaul company to perform this job?

[Hell Razor5543]

How mechanically competent are you? If you feel up to it you could try sorting it yourself. This is where I would start, if I had an autobox;

http://www.eastment.net/4hp20/4hp20_introduction.htm" onclick="window.open(this.href);return false;

[Wings]

Still struggling with the gearbox, all is fine until speed drops to 20mph round town then the final change down to first is clonky and sometimes under rapid breaking the final dis engagement goes with a clonk. I love the car, now the anti pollution warning is on with associated lights! no other symptoms engine runs and idles very smoothly. Just another puzzle. What fun! Ha. Ha.

[CitroJim]

Still struggling with the gearbox, all is fine until speed drops to 20mph round town then the final change down to first is clonky and sometimes under rapid breaking the final dis engagement goes with a clonk.

That's pretty much normal on a lot of HP20s.. I find they vary but all do it to a greater or lesser extent. It should not happen every time though, just occasionally.

What really seem to throw the 'box is if it thinks you're slowing to a stop and instead you accellerate away. That can cause a really clunky change.

[Mandrake]

I wonder if that clonk on changing down on the overrun is made objectionable by worn engine/gearbox mounts ?

My old V6 had fairly worn engine mounts and it did the clonk as described quite noticeably sometimes, my new one still does it but its far less noticeable, and the engine mounts are in a lot better condition - not surprising at half the mileage.

And yes, both the old and new one get caught out by suddenly accelerating just as it tries to change down from 2nd to 1st - I think that's a known shortcoming of the freewheel free design of the gearbox...