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        General >> Problems >> Autobox
        
(Message started by: PJDavis on Dec 11^th, 2011, 9:16pm)

Title: Autobox
Post by PJDavis on Dec 11^th, 2011, 9:16pm

Just a quicky. As a follow-on to what has happened in the past. Whilst driving the car at a steady speed around 3000 revs in O/D, very occasionally it feels as if it drops out of gear, and just as soon, it goes back into gear! No flashing O/D light, and otherwise the car drives like a dream whether I drive gently or thrash it. There doesn't seem to be any sort of definite formula to this problem, the fluid is clean, the MAF is clean, the only way I can describe, is as if I've taken my foot off the gas, then flicked the green button, and just as quick flicked it again, then the car drives perfectly again. There's no distant related formula either. It happened the first time about the time I last posted about the gearbox, it happened next just two days ago, I'm waiting for it to happen again! The car has always 'Fiddled-about' when doing just under 50mph with the O/D light out, almost as if it can't make up it's mind to change up or not, but I thought this was a common thing with the gearbox? Any discussion welcomed.

I might not be able to reply quickly though, because I'm going through a family bereavement at the moment.
Peter.

Title: Re: Autobox
Post by Glyn on Dec 12^th, 2011, 2:58pm

Peter, I don't know whether this is relevent but a few years ago I had a similar problem especially under load and it was said to be a cone in the gearbox associated with the overdrive. I had to have the box rebuilt with a new cone but this was on my 24v csworth and I was told it was more prone to happen on the cossie as the box is not exactly the same- I don't know whether this is true but someone will. They did look at the electrics first in case it was a faulty solenoid.
Glyn

Title: Re: Autobox
Post by PJDavis on Dec 12^th, 2011, 9:46pm

Thanks for the reply Glyn. Mine doesn't happen under load, in fact, the 'box seems to work at it's best when I've got my foot hard down in kick-down, it changes up smoothest all the way into O/D as well. It doesn't have a pattern, I've looked for that. In fact the first time it happened I had just tipped it out of cruise control because I was leaving a motorway. The second time it happened I was on a level throttle to just thinking of coming off the gas.

Title: Re: Autobox
Post by Aguc on Dec 13^th, 2011, 1:17am

Check the vehicle speed sensor (VSS) fitted near the output of the gearbox. My gearbox was thumping gearchanges somedays and smooth as silk otherdays. Recently however this culminated in NO gearchanges at all...1st and 2nd I could achieve manually but in "D" would loose drive completely like the box was in neutral!. I had to limp the car home 5 miles in 2nd. Checking things over at home I discovered the 3 wire pigtail from the speed sensor had corroded/broken away just as they exit the sensor. 2 wires were severed completely and the 3rd hanging on by 2 strands, fortunately as a quick fix I was able to remove the VSS and resolder the wires. The gearchanges are now seamless again. This may or may not be the root of your problems, but its so easy to check visually ...I think its worth a look. I have since aquired a new sensor to replace the repaired one.......the wiregauge used on these is really poor!
Happy hunting

Title: Re: Autobox
Post by PJDavis on Dec 13^th, 2011, 3:56am

Good info Aguc. I can check that. Is it on the near-side or off-side of the car? I looked at the diagram on here, how far back down the 'box is that lead?
Peter

Title: Re: Autobox
Post by Aguc on Dec 13^th, 2011, 8:44am

At the very rear of the box just in front of the prop flange. Looks like this.........
http://i192.photobucket.com/albums/z306/Aguc/IMG_0729.jpg
Above the heat shield.
Got this one through E-Dix the Ford old spares platform.

Title: Re: Autobox
Post by PJDavis on Dec 13^th, 2011, 9:10am

Jolly Good. I'll check that out as a start the next time I get onto the ramp at my work. (college)

Title: Re: Autobox
Post by Mike H on Dec 13^th, 2011, 1:44pm

on 12/11/11 at 21:16:16, PJDavis wrote:

The car has always 'Fiddled-about' when doing just under 50mph with the O/D light out, almost as if it can't make up it's mind to change up or not, but I thought this was a common thing with the gearbox?

No, mine did that but worse, a new MAF fixed it. (That is to say cleaning it did naff all, from which I concluded MAF was just "worn out")

The symptoms you describe are very similar, i.e. is thinking about changing gear while at a constant cruising speed when actually it shouldn't, what should happen is soon as it can pull O/D, it stays there, only changing down for a steep hill or if you've had to slow down to say < 30 - 40 mph, or if you boot it a bit. This is for 'E' economy mode.

As you hinted the converter lock disengages when you come off the gas, then when you go back on revs rise slightly for a second or so until the converter locks up again, but throughout, it should still remain in overdrive gear.

In fact it should try to hold O/D for most of the time as this keeps the revs low for best fuel economy.

I think the "cut-off" point is 2k rpm, problee about 40 mph, if it goes less than that then it's got to change down to 3rd at least.

Which BTW is so unobtrusive that most of the time I don't notice that it's even done it. Until it changes up to O/D again later. So I think "oh right so somewhere further back along this road it must've have changed down then." ;D

HTH

Title: Re: Autobox
Post by PJDavis on Dec 13^th, 2011, 10:18pm

I have kept the MAF clean, do it every 5k or there abouts, or even less than that if I think about it. In fact I cleaned it about 500 miles ago! I've got a brand new MAF but I reckon it's a pattern part, the supplier gives an instruction on how to fit it including disconnecting the battery for the prescribed time so that the ECU reverts to base. What is the correct way to fit a new Maf? Will a pattern part do the job? Should I disconnect the battery to re-set the 'whatever'? I also have a good condition MAF from a Mondeo, with the same numbers on it, it was working ok. I know what a dirty MAF behaves like, and the acceleration is crisp and throttle pick up is smooth and quick. I remember when the MAF was dirty the car ran like a dog!
Thanks for all replies so far. Peter.