Auto gear box question...

[simpT5]

Hi all, I'm looking for your opinions on my auto gearbox's odd behaviour!

My car is a 99 ME7 P1 V70 T5 with a four speed AW50-42 gearbox.

It changes up and down through all of the gears smoothly and shows no signs of flaring or slipping between the gear changes whether it's hot or cold.

The problem seems to be when the torque converter locks up when I reach speeds of 50mph and above. If I'm travelling at any speed above 50mph (which I often do!) and I lift off the accelerator completely, the torque converter then disengages and the engine rpm's drop slightly - normal. However there is a delay of about 2 seconds when I reapply the throttle while the torque converter sorts itself out and locks up again, during this time the engine rpm's rise slightly like it's slipping? It does this even if I reapply the tiniest amount of throttle too.

Just to confuse me further, if I accelerate from say 30mph, when I get to 50 it locks up perfectly with no delay, it's only when I lift off and reapply the throttle.

It's been like this for about a year/10k miles now and hasn't got any worse in that time, it's just recently started to annoy me!

The ATF fluid level is spot on, is dark red in colour and doesn't smell burnt.

I've had 15 litres of Dexron 3 fluid sat in my garage for over 6 months with the intention of changing it, but I don't want to make this problem worse by introducing fresh clean ATF into the equation!


Any thoughts or suggestions will be gratefully received thanks.
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[AndysR]

Are you sure it hasn't always done that. The torque converter never locks up straight away if your traveling at road speeds of more than 50mph letting off the throttle and reapplying regardless of throttle pressure.

[merc85]

You usually know your own car, especially over time, i would give the transmission a Oil change.

Let's face it it should be change at some point.

[simpT5]

Are you sure it hasn't always done that. The torque converter never locks up straight away if your traveling at road speeds of more than 50mph letting off the throttle and reapplying regardless of throttle pressure.

I've had the car just over 3 years now and I'm pretty sure it didn't do it when I got it!

[tim15888]

Sounds like the torque converter is draining itself for some reason, then having to fill back up when you give it big licks. Not that clued up on auto's too be honest, but a torque converter works by holding oil under pressure inside, and pushing the fluid round with the vains on the engine side, which then the moving oil in turn pushes the vains on the gearbox side round... If it's emptieng of oil then it would possibly do what you are describing.

[AndysR]

I've had the car just over 3 years now and I'm pretty sure it didn't do it when I got it!

Perhaps I am not understanding what your saying then. When you reapply the accelerator it takes a few seconds for the torque converter to reengage? If that's right I've had mine 4 years and it's always done it, my brothers S70 does exactly the same thing also and has done for the 3 years he's had it.

[merc85]

Perhaps I am not understanding what your saying then. When you reapply the accelerator it takes a few seconds for the torque converter to reengage? If that's right I've had mine 4 years and it's always done it, my brothers S70 does exactly the same thing also and has done for the 3 years he's had it.

Mine also done the same andy, but only when the Box got hot.

[AndysR]

Mine also done the same andy, but only when the Box got hot.

Are you saying its a fault or an operating characteristic? What I'm describing is an operating characteristic not a fault it does it hot or cold

[simpT5]

Perhaps I am not understanding what your saying then. When you reapply the accelerator it takes a few seconds for the torque converter to reengage? If that's right I've had mine 4 years and it's always done it, my brothers S70 does exactly the same thing also and has done for the 3 years he's had it.

Yeah it takes about 2 seconds or so to re-engage the torque converter and start accelerating again. I know this doesn't sound long but on a long twisty B road for example when you're constantly on and off the throttle it's quite annoying! Also with the revs rising slightly (about 500 rpm) for the 2 seconds whilst it engages, then dropping back when it does just doesn't sound right?

Hmmm you've got me thinking now lol!

[M-R-P]

Grabbing at ideas here... What mode is the gearbox in? (presuming it has the eco/sport modes)
Also, if the box mainly relies on mechanical feedback to an ecu, perhaps its just showing its age and responding to normal wear and tear. If its not slipping or flairing, I wouldnt worry but a tranny flush won't hurt.

[tim15888]

Sounds like the oil has gone thin and is draining from the torque converter then. If merc85's did it when hot, that supports the theory more, as ATF, like most oils gets less viscious when hot... Unusual fault though,

[AndysR]

Yeah it takes about 2 seconds or so to re-engage the torque converter and start accelerating again. I know this doesn't sound long but on a long twisty B road for example when you're constantly on and off the throttle it's quite annoying! Also with the revs rising slightly (about 500 rpm) for the 2 seconds whilst it engages, then dropping back when it does just doesn't sound right?

Hmmm you've got me thinking now lol!

Lol, well lock up is like another gear and usually accounts for around 400 ish rpm. Tbh it sounds normal to me perhaps you've never paid attention to it before and now you've noticed it you've become paranoid. Usually if something goes wrong with an auto the fluid condition is usually a good sign if something is up, also reverse gear will become clunky when selecting and general gear selection will become delayed.

[M-R-P]

Lol, well lock up is like another gear and usually accounts for around 400 ish rpm. Tbh it sounds normal to me perhaps you've never paid attention to it before and now you've noticed it you've become paranoid. Usually if something goes wrong with an auto the fluid condition is usually a good sign if something is up, also reverse gear will become clunky when selecting and general gear selection will become delayed.

Lol, mines a manual and acts like that! It's a LK tho...

[simpT5]

Thanks for the replies lads, most interesting!

Martin, my gearbox is the last of the 4 speed AW50-42's with just a 'W' button as opposed to the three sport/eco/winter buttons. I think it's supposed to be electronically adaptive or summat like that!

I like the theory of the oil losing it's viscosity when hot and draining out of the torque converter, makes sense I think!

I like to think I'm pretty handy with a spanner, infact I'm an auto electrician for a living but an auto box is one of the most complicated devices known to mankind!

Perhaps I'll change the atf (when the weather gets warmer!) and see what happens?

[tim15888]

Can't do it any harm lol. Alot of automajic cars you measure the oil levil with it running so the torque converter is full of oil... Not 100% sure about on these but are you measuring it runnung?

[M-R-P]

Thanks for the replies lads, most interesting!

Martin, my gearbox is the last of the 4 speed AW50-42's with just a 'W' button as opposed to the three sport/eco/winter buttons. I think it's supposed to be electronically adaptive or summat like that!

I like the theory of the oil losing it's viscosity when hot and draining out of the torque converter, makes sense I think!

I like to think I'm pretty handy with a spanner, infact I'm an auto electrician for a living but an auto box is one of the most complicated devices known to mankind!

Perhaps I'll change the atf (when the weather gets warmer!) and see what happens?

A flush won't hurt late. Empty, fill,.drive, empty, fill.drive etc. The more modern ones can be picky with new atf.

[simpT5]

Can't do it any harm lol. Alot of automajic cars you measure the oil levil with it running so the torque converter is full of oil... Not 100% sure about on these but are you measuring it runnung?

Yes, car on a level surface, atf up to temperature, cycle through each gear for a few seconds and back to park, engine still running and its bang on the max mark on the dipstick.

Maybe Andy is right about the paranoia theory!

I've read so many horror stories about cars being effectively scrapped through auto box faults, I'd hate that to happen to me as its taken me three years to get the car as I want it, both mechanically and aesthetically!

[M-R-P]

Yes, car on a level surface, atf up to temperature, cycle through each gear for a few seconds and back to park, engine still running and its bang on the max mark on the dipstick.

Maybe Andy is right about the paranoia theory!

I've read so many horror stories about cars being effectively scrapped through auto box faults, I'd hate that to happen to me as its taken me three years to get the car as I want it, both mechanically and aesthetically!

I know where you're coming.from there mate, have you seen my "is it worthit" thread?

[simpT5]

Yes I read your thread with great interest Martin!

Including the one where you took a chainsaw to your faulty dim in 'revenge of the skint'!!

Quality video that mate!

[tim15888]

Yes, car on a level surface, atf up to temperature, cycle through each gear for a few seconds and back to park, engine still running and its bang on the max mark on the dipstick.

Maybe Andy is right about the paranoia theory!

I've read so many horror stories about cars being effectively scrapped through auto box faults, I'd hate that to happen to me as its taken me three years to get the car as I want it, both mechanically and aesthetically!

What have you done to the car so far? Can't really tell from pics. Is it an ex-plod?