what speed/revs should my autobox change gear

[scanner]

so basically it will never go into top gear around town (30mph), i guess i get used to it along with the roll and how far to press the pedal out of roundabouts, have'nt got the hang of that yet, at least my left legs stop reaching for the clutch

Thats right, 1, 2 & 3 only unless you get over 37mph(ish)

So - If you only get into 4th at 37 does that mean you get 4th gear AND lockup at the same time.

AND if you drop out of lockup you drop straight to 3rd?

[Alacrity]

So - If you only get into 4th at 37 does that mean you get 4th gear AND lockup at the same time.

AND if you drop out of lockup you drop straight to 3rd?

No. 4th comes in & then lock up shortly afterwards (on a light throttle), it feels a little like another gear. It will come out of lock up & still remain in 4th when, for example you, start going up a slight hill.

[widdowson2008]

As stated the gearbox has 4 gears & it also has a lock up clutch in the torque converter (to prevent overheating & to aid fuel economy), It will select 3rd on a light throttle (normal town driving) below 30 & top at about 37. Lock up will come in a little later & feels like another (5th) gear (it isn't). At any point between light throttle & flat out the changes are infinitely variable as it depends on throttle position & road speed.

Thats the part I have been waiting for - 'lock up'. Excuse my ignorance, but apart from what alacrity has said (and so clearly) what does the 'lock up' actually do? - does it force the box to stay engaged in the higest ratio for as long as possible? and what causes it to 'un-lock'? speed/torque/road conditions(hills)?
This may be easy for you but I seem to be on a perpetual learning curve with the Bongo.

[scanner]

It locks the torque converter so it no longer "slushes" - top gear is then fixed just like when the clutch is fully engaged on a manual car.

[widdowson2008]

Cheers scanner - almost there
what causes it to 'un-lock'?
(please excuse my ignorance)

[scanner]

Cheers scanner - almost there
what causes it to 'un-lock'?
(please excuse my ignorance)

Anything apart from keeping your foot down - so it would seem.

[widdowson2008]

Thanks scanner - sorry Darkstar - back to thread

[Darkstar]

dont know a thing about automatics, so any info about them is interesting, i'm sure

[Alacrity]

The lock up is controlled by the gearbox ECU via the gearbox valvebody, it is switched in & out as engine load (throttle) & road speed alter the demands on the gearbox. It doesn't happen at any fixed point but is variable to avoid overgearing judder. If you back off the throttle at, say for example 60mph, it will disengage then you feel it re-engage as you return the power.

When 4 speed overdrive units first came into being in the 80's they found that they would overheat when on a motorways & loaded due to the fact that the torque converter would start 'working' (i.e. multiplying torque) at speed & generated massive amounts of heat. The lock clutch was introduced to stop this & had the added benefit of improving fuel consumption as a fluid coupling such as a converter will always have a degree of slip in it no matter how close the clearances are. It simply locks the converter internals together giving solid drive from the crankshaft to the wheels.

As I have mentioned in other posts on the forum it is a early style very crude system on the Bongo.

[Tripewriter]

Lock-up is a myth, what you mean is overdrive which you force to engage by whizzing up to 40 then backing off the throttle.

[Alison01326]

I know even less than everybody, so I am going to ask an even simpler question than Steve did Is lock up when the engine sounds like it has "relaxed". That's about the only way I can describe it. It happens in pretty much the same place every day (provided I drive along the same bit of road, which has a 40mph limit and is on a slight upwards incline). The engine note changes and the revs drop a bit. Is that it?

Just curious.

You can get back on thread again when I've had my answer

[scanner]

I know even less than everybody, so I am going to ask an even simpler question than Steve did Is lock up when the engine sounds like it has "relaxed". That's about the only way I can describe it. It happens in pretty much the same place every day (provided I drive along the same bit of road, which has a 40mph limit and is on a slight upwards incline). The engine note changes and the revs drop a bit. Is that it?

Just curious.

You can get back on thread again when I've had my answer

Sounds like it and from that point on do the engine speed and road speed seem to be "locked" together?

[Alison01326]

Yes, Scanner, they do. Thank you.

[Alacrity]

You can always tell if it is in lock up by gently moving up & down on the accelerator pedal (just slightly, don't back right of or it will come out of l/up) when over lock up speed (roughly 40mph ish on level ground not accelerating anymore), and the rev counter needle shouldn't move it should remain steady. Try it at say a steady 30mph & you will see the rev counter needle dance about as you do it (slip in the converter).

As I say in all the Bongo's I have driven it feels like another gearchange a short while after it has gone into 4th (when the engine has some warmth in it).

[Velocette]

Very generally speaking low revs in high gear doesn't necessarily mean maximum economy. If the engine is designed to cruise at higher revs it will not be working efficiently, a bigger throttle opening will be needed and more of the fuel will go through the engine unburned. This seems to bear out in the results I got from my manual car and motor bike when I switched to 3rd gear in 30mph zones instead of top when I had points on my license and didn't want any more. I wasn't really going much slower. just that it is easier to stick to 30 by ear that way. My fuel consumption was no worse, possibly better.

This thread is very useful by the way and explains a lot. My Bongo does not seem happy if I feather the throttle, and I have to use hold if I am doing a steady 40 or 50 or if I am behind slow traffic or it hunts and "unlocks" I think. If I can just put my boot down and do my own speed it is much better. I do have some transient problems with the gearbox because the hold light flashes sometimes usually preceded by delayed changes jerky changes and hunting. It is going into ADS to be checked,