Afternoon all, 

Bit of a strange one today, recently had a replacement gearbox installed in a 2013 mk3 focus 1.6 6 speed diesel. 

As you know, on the dash the car suggests when you should change up or down a gear. The issue is that the car will now suggest that i switch into a gear that I'm already in. Driving down the motorway in 6th with the car constantly asking to change up to 6th.

Would anyone know how this might be fixed and if its a big job? 

 

Thanks in advance all

This indicates that the actual speed/RPM ratio does no longer match the ratio that is programmed into the PCM software.

This can be caused by a slipping clutch but because the gearbox is recently replacement it is highly likely that the replacement gearbox has an incorrect gear ratio or final drive ratio.

Since the programmed gear ratio's are deeply embedded into the PCM software this can either be solved by custom written PCM software or by replacing the gearbox for the correct one.

It does sound like you have the wrong gearbox. As @wilcosays the PCM needs new parameters which is beyond the ability of most of us. If the car seems to drive 'ok' (you're going to get less mpg) and the only issue is the annoying little light on the instrument cluster then I would be taking the IC out, opening it up and putting a bit of black tape over the LED. Not a perfect fix but better than having to change the gearbox again.

If the car has Cruise Control the Cruise Control will be switched off once the PCM detects a non matching speed/RPM ratio.

Getting rid of the shift indicator is pretty easy. Just disable it inside the CCC (Central Car Configuration) using a suitable diagnostic system.

You might find that if the gearbox ratios are different, your engine revolutions might be higher than expected for the given speed.  This will cause some increase in fuel usage, and engine wear, and reduce oil life slightly.  I’d be making sure you get this gearbox checked against the original if you can, and swap it out if its not correct.  Turning off the gear change light is just hiding the problem, not rectifying it.  

You may also need to inform your insurance company, as strictly speaking, the drive train is now modified for a different final drive ratio, and hence speed.  Out of curiosity, I don’t know how the speedometer works in fords, but the Subaru I had a few years ago used a sensor on the final drive from the gearbox, so this reading might be out too.

Thanks for the replies lads,

Based on what you've all said, i spoke to a mechanic friend of mine and he believe that it's possible that the second hand gearbox i got from a breakers yard is a petrol version and not a diesel model. Any idea if this could be the case?

If it's helpful, i have noticed the car revving at 2800 rpm at 70mph, and im really sure it was closer to 2000rpm before the gearbox change.

 

Thanks again lads

Since the Ford B6 gearbox that your car has was also used on the 1.0 ECOboost (125 HP and 140 HP) and 1.5/1.6 ECOboost (150 HP and 182 HP) it is perfectly possible that you have installed a B6 gearbox from a petrol version.

Apart from this there is also difference in gear ratio's between the 1.6 TDCI ECOnetic engines and the regular 1.6 TDCI engines.

15 hours ago, Defianse said:

If it's helpful, i have noticed the car revving at 2800 rpm at 70mph, and im really sure it was closer to 2000rpm before the gearbox change.

That’s a sure sign that it’s the wrong gearbox, and that increase in revs at 70mph will be costly in fuel, and wear.

 Diesel engines don’t rev as high, redlines usually around 4500-5500 where as petrol can often go up to 7000rpm, and some even as high as 9000 like the old Honda S2000. If you’ve fitted a petrol box, the ratios will be way out, and you might find some gears are totally useless, because of the torque of the diesel.

I’d be dropping that box out and getting the right one in, pronto.

On 8/30/2021 at 11:00 AM, Jus1973 said:

You may also need to inform your insurance company, as strictly speaking, the drive train is now modified for a different final drive ratio, and hence speed.

No need, the car will be slower.

5 hours ago, unofix said:

No need, the car will be slower.

Most insurance companies don’t care if its faster or slower, more that its no longer ‘stock’. I’d hate for the OP to be involved in an accident and then later find he wasn’t insured through not making a simple phone call to check.