Dipping

[ken newbold]

Who are "those that know" though - do they actually? Logically, keeping it in D whilst stationary creates frictional effects and heating. Clearly the box is having to dissipate unnecessary energy amongst other things. I always go to N at lights and it's benefit can be seen on the oil temperature guage. I imagine too, correct me if I'm wrong, that it probably keeps the valves and oilways with less risk of congestion if they are usually operated?

Ok had a sniff around and this is from the Rospa driving manual.....

When stationary in traffic, even for many minutes, it is not necessary to move the gear lever into neutral because the torque converter absorbs the engine’s propulsion force but does not transmit it all to the gearbox. No wear is taking place. In fact, more wear will take place if you engage neutral then engage a drive gear when it is possible to move off. Most gearboxes will automatically select first gear when the vehicle becomes stationary.

I had an auto box in my GTi once. Terrible power draining things. But very enjoyable around town - apart from the fuel consumption.

That figures.
I guy I know who only has an auto licence always puts his in neutral even when at traffic lights. He's gone through more gearboxes than I can tell you about.

[mike st gilles]

Ken said <That figures.
I guy I know who only has an auto licence always puts his in neutral even when at traffic lights. He's gone through more gearboxes than I can tell you >
Got to agree, my b in law bought my wifes 924 auto (horrid thing) which had had no probs at all during its time with us and was probably one of the better 3 spd autos I've driven (excepting those at work ). Within a short space of time he was ringing up asking if we'd ever had probs re the auto box as it was making strange noises.....found out he was doing the shifting into N bit at lights etc. I advised him re the habit and he disagreed despite my experience and quals. Paid for it with a new/recon g/box and got rid shortly after.
Re the AIM bit....... some of it is a bit outdated agreed but I don't think you'll find that any of it is actually wrong and the bit re the auto box is probably very relevant to Phil's car as the gearbox is basically the same as those referred to.
I've owned many autos in the past and do at this moment have 3 in the household; 03 Hyundai Santa Fe auto diesel 90k, Honda CRX vtec Auto 42k and my BX 19tzd Auto 240k (kms) and I have never shifted into neutral at lights etc and never had a problem.
Nor have I with any of my past cars many of which were old Merc autos many with astronomical mileages.
I have driven probably hundreds of thousands of miles in my past occupation many of which in fairly high powered automatics and again never put the car into N at lights.
Neutral should never be used for coasting.
In fact cars should never be coasted full stop; manual or auto.
If at a stop in drive the car is noisy (vibration etc) then the idle needs adjusting or a stepper motors not working to raise the idle with the gear engaged or something as the car should be ok to wait at lights without being shifted into N. Normally (old) autos have a higher idle speed to combat this problem.

[DLM]

Just one observation: I'd be sure to do one step at a time in trying to isolate causes (unless of course you're paying for the work each time, when different considerations may come into play).

On the "bleed rear brakes" suggestions, I've personally never had any experience of sink at the rear as a consequence of air in the rear brake circuit - just raising of the rear under braking. But it can't do any harm to try this first, assuming that the bleed nipples haven't been left to fester.

Also, have the rear suspension cylinders ever been replaced during the life of the car?

[Philip Chidlow]

Thanks for the advice. I have a few things to check now.

And no more shifting into N! The vibration isn't cured by altering the idle speed. I will report back when we get to the bottom of it.

[Aerodynamica]

I've personally never had any experience of sink at the rear as a consequence of air in the rear brake circuit - just raising of the rear under braking. But it can't do any harm to try this first, assuming that the bleed nipples haven't been left to fester.

It's certainly what I've experienced over the various cars I've had - It's caused by the higher pressure of the LHM supporting the rear suspension meeting the low pressue, (relatively) large volume bubble of air in the brake lines or in the caliper pot itself. As soon as the brake valve opens to connect these two the higher pressure LHM from the suspension compresses the bubble to a tiny dot but this loss in volume causes a loss in rear end height.

Only on my Xantia did I get the lifting up tail characteristic through unbled brakes but even after it had jumped up the brakes would then bite at the back (late) and the rear end then fell to the floor - it always went lower because it would then compensate by jumping back up half as much.

Lots of fun

[retrodriver]

I was always told by those in the know when I used to run old BMW automatics that shifting into N at lights is bad for the gearbox as it may not be being cooled properly, that was on the old ZF4 HP... boxes, and I believe the BX runs a ZF 4 of some type. I certainly never shift into N at lights when driving any auto, ive been told not to by an autobox repair man so he should know! Also when the car is in D, the pressure is constantly correct, the bands and valves are working properly and everything is being nicely lubricated. Certainly old BMWs used to be able to blow the autobox if you constantly revved them hard in park, as the pressure would build in the system and wouldnt be released until a gear was selected.

A mate of mine is on the way to ruining the box in his Audi A4 Quattro, he slides it into neutral and coasts in on the handbrake!! It was smooth as silk, now its clunky and whiny, proof enough for me!

On point...I sometimes find that if I come tearing upto some lights and dont release the brakes until I move off, the back of my BX jumps, my rear spheres are new and fully bled out so I suppose its normal?!

[docchevron]

Ok, if I'm going over whats already been said, deal with it, it's late, I camt be arsed to read it all and I'm a bit pissed.
But in short, yes, leave the thing in D. It causes alot more stress and wear to the box to move between D and N all the time.

Also bear in mind that ZF's are F clever boxes.
When it's stationary in gear NOTHING other than the oil pump and torque converter are moving. The epicyclic is entirely still.
Therefore, unless the car is idling at 3000RPM or some such the heat build up caused by holding it in gear is sweet FA.
Conversley, selecting N and sitting there idling allows both halves of the converter to spin, and with the brake band relased the box itself will of course rotate with a much reduced oil flow than at higher engine speeds.
Wear on the brakeband and hydraulic clutch pack will increase by going from N to D etc often since the as the car is at a standstill the output shaft is stationary and therefore the internals that are happily spinning around freely in N have to be brought to a halt.

Ok, this over simplifies things a bit, but you get the idea.
Of course if you have a proper ZF, like a 5HP500, then you can leave it in Drive for ever at idle, since they are the gearbox of winners.
I have 2.

As for the juddering when stationary in D, could be one of a couple of things really.
You say it doesn't improve if you increase the idle speed yes?
It could be the kickdown cable wants adjustment, I've yet to find one thats actually been right (except dads of course), and you would not believe the difference that innoffensive cable makes to how well the box works, or doesn't.
Does it feel like it slips at all if you boot it in any gear except for top?

[Philip Chidlow]

Does it feel like it slips at all if you boot it in any gear except for top?

Nope. In fact it seems to be working fine except for the idle in D vibration. I will make sure the kickdown cable is adjusted correctly. I'm lucky there's a chap locally who is a Citroen veteran and auto box specialist.