P38 auto box gone sticky

Hi all,
This could very well be in my head, but I've got a feeling that my gearbox has changed character lately. It takes off and changes up just like it should, but then stops short of the last cog. It sits at 2100rpm at 80kph for about 5 minutes until it's properly hot, then changes up. After this it works perfectly. So this only happens from cold. It might have been like this always, but I don't think so. I topped up the ATF yesterday but it made no difference this morning.
Any ideas? FYI, the car is a 97 4.6 HSE.

Cheers,
Henrik

Change the fluid and run for a week, then change again and the filter and stick some Lucas in it.

When was the oil and filter changed? That last gear at 80kph is actually the torque lock up, the actual speed at which it locks up varies with load and throttle opening as well as speed, so for example, a binding brake could affect it, so could heavier boots.

Datatek said:

When was the oil and filter changed? That last gear at 80kph is actually the torque lock up, the actual speed at which it locks up varies with load and throttle opening as well as speed, so for example, a binding brake could affect it, so could heavier boots.

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Hah! That explains why I've counted five gears even though I know it's got only four
It behaves as you describe once hot, i.e. changes up or locks up when I ease off the throttle. It won't lock up when cold though. The fluid and filter were changed two years ago, so about 30.000km. I will try Wammer's cure and hope it sorts it.
Thanks!

Henrik97 said:

Hah! That explains why I've counted five gears even though I know it's got only four
It behaves as you describe once hot, i.e. changes up or locks up when I ease off the throttle. It won't lock up when cold though. The fluid and filter were changed two years ago, so about 30.000km. I will try Wammer's cure and hope it sorts it.
Thanks!

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Not sure on the 4HP22/24 but on the 5HP24, it employs a 'Warm Up' procedure where it holds the lower gears for longer to aid in warming up the fluid/box and then reverts to a normal shift pattern....

Do the 4HP's do similar??

Saint.V8 said:

Not sure on the 4HP22/24 but on the 5HP24, it employs a 'Warm Up' procedure where it holds the lower gears for longer to aid in warming up the fluid/box and then reverts to a normal shift pattern....

Do the 4HP's do similar??

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Well, that would certainly explain it. It works perfectly when warmed through, so this sounds like a plausible explanation. Hoping it's not just wishful thinking....

it should be sticky valve

Henrik97 said:

Well, that would certainly explain it. It works perfectly when warmed through, so this sounds like a plausible explanation. Hoping it's not just wishful thinking....

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Reading RAVE and the EAT operation - doesn't look like the P38 used a 'Warm Up' shift Pattern....

It does state that gear change durations can increase due to component wear, and the Hydraulic System tries to modulate hydraulic pressure to the valves to adapt to the wear....but these will no doubt only last so long!

Henrik97 said:

Hah! That explains why I've counted five gears even though I know it's got only four
It behaves as you describe once hot, i.e. changes up or locks up when I ease off the throttle. It won't lock up when cold though. The fluid and filter were changed two years ago, so about 30.000km. I will try Wammer's cure and hope it sorts it.
Thanks!

Click to expand...

So, the fluid and filter are due a change. Mine certainly holds lower gears longer when cold but there's no chance to check the lock up as I can't get to that speed round the lane where I live before it warms up.

My 4.6 will only go up to 4th until the temp gauge reaches just before the middle, after 5 mins or so. Then the lock up will engage at 40 mph every time until the engine has cooled again, usually the next day. Its done this as long as I've had it. I assume its normal

stewie said:

My 4.6 will only go up to 4th until the temp gauge reaches just before the middle, after 5 mins or so. Then the lock up will engage at 40 mph every time until the engine has cooled again, usually the next day. Its done this as long as I've had it. I assume its normal

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The 4.6 is different, it has the 4HP24 box not the 22 and the ECU is different. Lock up occurs at around 50mph on the 4.0 and diesel with the 4HP22 box.