How exactly does the autobox determine when to change from overdrive/fourth to third gear.

 

Mine seems to be doing it even when cruising or in cruise control the second a slight incline is met leaving me to cruise around in third for most of the time. MPG is bad enough with the overdrive.

yeah that happens on ours, it seems pretty wierd, set the cruise on a motorway and the second it gets to a hill it shifts down, soon as it gets flat again it shifts back up.

Anyone explain why the hell it does that?

Wish i could my cruise control has never worked do you guys use it often????

 

Marc:confused:

hardly ever, when it does get used its only on long tedious motorway journeys.

Its hard to use it on UK motorways as you have to change speed all the time. When I use it its only for 5 mins at a time so I can move my feet a little.

 

 

Stuart

The handbook warns of this shunting in and out of overdrive at certain speeds on an incline etc. It recommends dropping out of overdrive if shunting in and out is uncomfortable.

 

Its normal.

 

It decides based on speed, engine rpm, and throttle position.

Oh so im not missing much then,oh well i have a auto anyway that saves the legs in the long runLOL:D

 

Marc

No

 

I dont mean the normal operation of the overdrive i meanat cruising. The instant cruise is put on it dros to third.

 

When cruise isnt on and i barely touch the accelerator she drops to third. Can only drive in overdrive if I barely touch the accelerator.

 

Any ideas whats causing this drop????

Sounds like a kickdown problem to me. sensitive switch maybe?

maybe worth checking the tps. If it is giving the ecu the wrong throttle opening signal then this could do it. Sounds like its telling the ecu its open much more than it really is. See manual get a voltmeter and check it - also check the connectors for corrosion and bad contact. Another poss is the speed sensor saying you are going much slower than you really are but then the speedo might also read slow if this was true.

I do alot of motorway miles and the switching down doesnt bother me at all, the car just wants to put less strain on itself so it switches down, clever old thing.......:D :D

If you have a Jap Auto, you can put in Hold and it should reduce it changing gear as often. Seems to make my box feel much smoother as well.......?

 

(And I found it a good way to check boost, as you can floor it without kickdown, and get reasonable operation in boost before hitting warp speed!!!)

 

StuartR

When cruising on light throttle it should be in OD top and locked up - 2700rpm ish at 80. It doesnt just drop a gear to put less strain on itself when there isnt really any strain. The only time it'll drop out and drop to 3rd is on an incline or something when you or the cruise control will open the throttle a little to maintain the speed.

 

I dont think you can put a hold on a UK auto. Mine always drops a couple of gears on kick down, then red lines before changing up.