Jatco in sport mode

[SteveThackery]

Colleagues!

I've been playing around with Sport mode on my 2.5 KV6 automatic. Strangely, it doesn't seem to ever go into top (5th) gear when Sport is engaged.

I drove it at a steady 85-ish (indicated) with a very light throttle, and even after several minutes of a steady speed it remained in 4th gear. This is nothing like my Lexus, which engages top gear easily enough even in Sport mode - the only difference is it changes down much more readily and holds the lower gears slightly longer.

I know the Jatco box was still in 4th gear, because the moment I disengage Sport mode it changes up into 5th.

The transmission seems to work OK in every other respect (still some slightly jerky changes, though much improved after an oil change). Is this hanging on to 4th gear normal for our cars?

[xsport]

Yes thats correct. Stays in fourth to utilise the full power of the engine. Other things come into play as well with regards the tune and gearbox .Quite enjoyable on the motorway, but heavy on the pocket !:icon_

[SteveThackery]

Originally Posted by xsport

Yes thats correct. Stays in fourth to utilise the full power of the engine. Other things come into play as well with regards the tune and gearbox .Quite enjoyable on the motorway, but heavy on the pocket !:icon_

OK, thanks for letting me know, xsport. Much appreciated.

[jon cee]

recently had a 160 remap done by Terry of TS Autos, I only have the 2.0cdti auto MG ZT-T, and didnt put it in Sports mode till a few days ago. but Mine stays in 4th gear too at 80 - 90 ish ...
I hadnt give it a thought when i did the remap, 'what might change regarding the different AUTOMATIC modes' ... but I've since spoke to terry and he told me 'the gear ratios remain the same, they are set using mechanical plates/cogs and pressures, they are set using its own part of the ECU seperate to the part of the ECU remapped ... they broaden the limits of the boost within the ECU, fuel pressure remains the same', so if my 2.0cdti is still in 4th at 80mph too, and you have the 2.5L V6, id imagine in sports mode its going to hold on to 4th gear comfortably until about 90-100mph ...
regarding fuel economy, I wouldn't sit at 80+ on the motorway, in sports mode, use sports mode to get you there quicker, then once at the required speed, move back into Economy (drive) mode.

[SteveThackery]

Originally Posted by jon cee

I wouldn't sit at 80+ on the motorway, in sports mode, use sports mode to get you there quicker, then once at the required speed, move back into Economy (drive) mode.

Yes, totally agree. It does make sense to switch out of Sport mode as soon as you're up to speed. I think Rover made a bad decision by preventing the use of top gear when in Sport mode; it's the only automatic I've ever owned that does that.

To be honest I'm still not entirely happy with the gear change on mine, although changing the transmission fluid does seem to have improved it. Mine seems reluctant and slow to kick down, and sometimes when it does, it does so with an alarmingly vicious jerk. I've started using the selector to manually change down to 4th or 3rd when I need a sudden burst of acceleration (such as on a slip road) and those changes are pretty smooth.

[Southern Star]

Most motorcycles achieve their maximum speed in the next gear down from the highest so I suppose it makes sense.

[SD1too]

Originally Posted by SteveThackery

Mine seems reluctant and slow to kick down ...

Hi Steve,

I recognise that. Two things:

Have you looked at the VIS balance flap recently? Check that it isn't stuck in the mid-position and that it moves freely with the lightest touch of your little finger.

Removing the cam covers and clearing the breather hole behind the gauze filter of carbon deposits made a dramatic difference to my automatic downchanges.

Simon

[SteveThackery]

Originally Posted by SD1too

Hi Steve,

I recognise that. Two things:

Have you looked at the VIS balance flap recently? Check that it isn't stuck in the mid-position and that it moves freely with the lightest touch of your little finger.

Removing the cam covers and clearing the breather hole behind the gauze filter of carbon deposits made a dramatic difference to my automatic downchanges.

Simon

Hi Simon! I've just recently fitted two new VIS motors, which gave me the opportunity to check the balance flap and the actuating lever for the power flaps. I did give the balance flap a fettle with some wet 'n' dry. I didn’t open the chamber to check the six power valves, but the lever feels OK. Finally I checked both motors by earthing the appropriate terminal on the connector, and they both sound like they are operating correctly.

Thanks for the tip about the cam covers. I will definitely try that as soon as I can get the front of the car under cover (I'm waiting for the men to fix the garage roof). What is the mechanism by which those breathers affect the gear changes?

[SD1too]

Originally Posted by SteveThackery

What is the mechanism by which those breathers affect the gear changes?

I've no idea Steve!
What I have learnt along the way is that if the engine "tuning" isn't spot-on the automatic gearbox won't like it. The danger is a misdiagnosis that the gearbox is at fault.

Many years ago my SD1 developed a fault where the gear change from 1st to 2nd was hugely delayed. Another owner showed me a perished rubber sleeve joining the inlet manifold to the pipe leading to the vacuum modulator. That's all it was; nothing wrong with the gearbox at all.

Simon