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Old 16th August 2018, 17:22   #1
minty2
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Default Normal Jatco behaviour?

Not really a cry for help but for opinions. I've had my Rover 75 2.5 KV6 (174 ps) automatic tourer for almost four years and apart from the abysmal fuel consumption, I've been very happy with it. While driving through Germany, I've been able to 'let her go a bit' and achieved speeds that I would never dare attempt in the UK. But one thing it's highlighted is the (on my car) annoying behaviour of the autobox seeming to change up from 5th to a mysterious '6th' gear while accelerating in 5th and holding the car back unless I blip and hold the throttle down to counteract it (it usually drops down into 4th). I think this 6th gear is actually the direct drive mechanism cutting in; it has the effect of dropping the revs a bit and I can feel the car holding back in 5th. Normally, this doesn't bother me, but on the autobahn, there's nothing worse than accelerating to overtake someone and finding the gearbox holding you back (unless I kick-down to or manually select 4th). Even then, it has the equally annoying habit of changing up too quickly (unless I keep in in 4th). My guess is that this is all completely normal behaviour that I've got used to on our slower roads, but I just wanted to confirm it.
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Old 16th August 2018, 17:51   #2
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Sounds like you are experiencing the lock up of the torque converter, mine does it around 65 -70 mph. perfectly normal
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Old 16th August 2018, 17:52   #3
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In these moments when you've got the 'need for speed', use Sports mode. It will change up at around 2200 rpm normally, hold onto fourth until 65 ish and generally kick down eagerly. Even in top gear.

All these figures from a dizzle auto. Yours may be a bit different.

I find the D mode quite frustrating as it is hell bent on changing up at the earliest opportunity, but have learnt to live with it (it is economy mode after all) and use Sports mode when I want better response and as you said use D3 and D4 when I want to be in total control.
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Old 17th August 2018, 07:04   #4
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Torque converter lock up, there to mechanically lock the box to the engine and save losses in the fluid link between them.

Pretty normal and always felt a bit slow at disengaging to me but hey ho.
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Old 17th August 2018, 07:46   #5
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Quote:
Originally Posted by first-things-first View Post

All these figures from a dizzle auto. Yours may be a bit different.

The KV6 auto definitely needs to change down more often for a decent burst of acceleration, including getting the VIZ motors working at their best. It's just that in economy 'D' mode, it does like to change up too quickly again!
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Old 17th August 2018, 19:24   #6
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David,

Have you checked that the pinhole restriction in your cam covers is clear lately?

Simon
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Old 18th August 2018, 07:37   #7
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Quote:
Originally Posted by SD1too View Post
David,

Have you checked that the pinhole restriction in your cam covers is clear lately?

Simon
About six months ago, when I checked the breather pipe.
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