OT Auto boxes and engine revs

[Capitol]

That's the Chrysler 4 speed auto box used in the Intrepid cars and the Voyager people carriers. It is very smooth most of the time, but doesn't like rapid up/down changes. The flex plate on these is a bit iffy and can give all the symptoms of a duff gearbox if it bends so that the timing sensor misses pulses. The only solution is a new flexplate. It's a difficult design decision setting the hardness of the flexplate, too stiff and the torque converter distorts, too soft and the flexplate bends. my experience of these units has been very satisfying.

[Capitol]

That's the Chrysler 4 speed auto box used in the Intrepid cars and the Voyager people carriers. It is very smooth most of the time, but doesn't like rapid up/down changes. The flex plate on these is a bit iffy and can give all the symptoms of a duff gearbox if it bends so that the timing sensor misses pulses. The only solution is a new flexplate. It's a difficult design decision setting the hardness of the flexplate, too stiff and the torque converter distorts, too soft and the flexplate bends. my experience of these units has been very satisfying.

[Andy Burns]

Mine will brake if it goes more than 2mph over the set speed, if you put your foot down to deliberately exceed the set speed, it refrains from braking when you let it take over again, until it's been down to the set speed, the ABS servo is used, you can hear the solenoid clicking, it also "wipes" the brake discs so there's no delay for them to dry off if it's wet

Given many people drive the same route over and again, surprised the cruise doesn't learn where oncoming hills are from the GPS, and then depending on if you're in sport or eco mode it could keep speed up, or go for economy,

[Dave Plowman (News)]

Will probably be in top at 60, unless till accelerating.

I'm not well up on the later 4HP22. Early versions were very basic but later gained electronic control. My 5HP which is on an earlier vehicle does drop a gear or two going downhill if it is running away and you touch the brakes.

If you're not used to an auto but observant of how an engine etc behaves, they can get some getting used to. Some are absolutely brilliant - doing more or less what a good driver would do with a manual - but some not so good. With modern computer control it should be easier to get a good match between engine and box.

[The Natural Philosopher]

I do remember my XKR changed up to 3rd at 100mph. In sport mode. Sigh. What a fantastic waste of money that was.

[David]

(snip)

I thought you had a 1997 528i E39 ???

David

[Scott M]

And before that he _had_ an E34 525i...

[Dave Plowman (News)]

Had an E34 before - the first production car with the 5 speed ZF, IIRC.

[David]

David

[David]

Thanks, see below

David

[newshound]

Seven "steps" on the paddles of the Jazz; with software to prevent over or under revving. Left to its own devices, the ratio shifts smoothly, giving a feel (and sound) rather like having a gas turbine under the bonnet.

[Vir Campestris]

Many modern diesels don't have any low-down torque.

My son has an Astra diesel. When driving it around he's forever changing gear, because the power band is so narrow. It needs those 6 gears.

Andy

[bert]

Just like a DAF!

[bert]

You do surprise me. I have bee impressed as to just how flexible by Puma engined Land Rover Defender is.

[John Williamson]

A lot of modern diesels do have a narrow power band, as it's a cheap way to keep the emissions within the required limits.

On coaches, it's now not unknown for the manual and automatic 6 speed boxes of not many years ago to be replaced by 12 speed auto boxes, which are in fact a computer controlled manual box and clutch, to keep the engine within it's acceptable rev range.

[The Natural Philosopher]

there are diesels and there are diesels and there are turbo diesels too.