957 Turbo 3rd gear slip
#16
10-17-2018, 08:08 AM
I just posted a subject very similar to this, but I experience it in 2nd gear, after a fluid change (see my post).
However, in 3rd I believe this is normal, I dont think its slip, its the torque converter locking up. Are you still floored when you feel this rpm drop again? I would think it should not lock up until you lift a bit on the accelerator?
Easy way to check this is or get a feel for it to see if its similar to what you are experiencing, is to put the selector in manual mode, so it holds a gear, then in 3rd, 4th, 5th or 6th, drive along at a constant speed, then step on the accelerator to the point you feel that last little click in the pedal (full kick down), and since your in manual mode, you will not change gears, but you will feel what is like a gear change, rpms will increase as the torque converter is unlocking. So you are sill in the same gear, but at a higher RPM cause you are no longer 1:1 (engine and tranny). I confirmed this is the case in 3rd, 4, 5,6 per my icarscan, torque converter disengages when you feel this rise in RPM (slip is no longer 0).
Also, per the 09D transmission literature I have found, TC locks in 3, 4, 5, 6.
My 2014 Volvo XC90 did the same thing (also has an Aisin trans).
However, in 3rd I believe this is normal, I dont think its slip, its the torque converter locking up. Are you still floored when you feel this rpm drop again? I would think it should not lock up until you lift a bit on the accelerator?
Easy way to check this is or get a feel for it to see if its similar to what you are experiencing, is to put the selector in manual mode, so it holds a gear, then in 3rd, 4th, 5th or 6th, drive along at a constant speed, then step on the accelerator to the point you feel that last little click in the pedal (full kick down), and since your in manual mode, you will not change gears, but you will feel what is like a gear change, rpms will increase as the torque converter is unlocking. So you are sill in the same gear, but at a higher RPM cause you are no longer 1:1 (engine and tranny). I confirmed this is the case in 3rd, 4, 5,6 per my icarscan, torque converter disengages when you feel this rise in RPM (slip is no longer 0).
Also, per the 09D transmission literature I have found, TC locks in 3, 4, 5, 6.
My 2014 Volvo XC90 did the same thing (also has an Aisin trans).
#17
01-25-2023, 08:30 PM
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Just a thought fom my own experience
Update from dealer, they tested another vehicle with 60000km on the clock and they said exactly the same symptoms, obviously the car just has the same problem in my mind, i could be wrong not being an expert in these vehicles.
So they are officially stating that the slip is from the gearbox deciding that there isn't sufficient torque available when going up the hill and instead of changing down it is slipping the gear, bear in mind this only happens in 3rd. Most exaggerated going up incline but also present when accelerating medium to high in third. I don't get this at all when I disable PSM, or switch to manual mode. In fact PSM mode off is so good I might just stay there.
Is there any way to prove this is a gearbox issue, some kind of monitoring or dyno run. Have you had this problem, please could someone run this simple test, just look for a steepish uphill and as it changes to third apply a bit more throttle and keep it there, then just check your revs and see if they rise then fall then rise again before 4th.
Or anyone in JHB or pretoria that we can compare with.
I would think if its the valve body then it should also happen when in manual mode, but perhaps the software is locking the clutch.
thanks for the replies so far.
So they are officially stating that the slip is from the gearbox deciding that there isn't sufficient torque available when going up the hill and instead of changing down it is slipping the gear, bear in mind this only happens in 3rd. Most exaggerated going up incline but also present when accelerating medium to high in third. I don't get this at all when I disable PSM, or switch to manual mode. In fact PSM mode off is so good I might just stay there.
Is there any way to prove this is a gearbox issue, some kind of monitoring or dyno run. Have you had this problem, please could someone run this simple test, just look for a steepish uphill and as it changes to third apply a bit more throttle and keep it there, then just check your revs and see if they rise then fall then rise again before 4th.
Or anyone in JHB or pretoria that we can compare with.
I would think if its the valve body then it should also happen when in manual mode, but perhaps the software is locking the clutch.
thanks for the replies so far.
#18
01-25-2023, 09:24 PM
Yea the aisin tranny ruined what would have been the perfect ride in the 957 and 958 CTTS for me. I now have an F85 X5M and the ZF is a perfect transmission. Wonderful in every aspect.
#19
01-28-2023, 07:24 PM
EDIT: ifailed to remember I already posted to this up a few.
at least my response is consistent.
Assuming its behaving like i think you are describing, its normal torque converter operation locking and unlocking.
I have the same situation every day going up a gentle hill and avcelerating in third and do not have the problem you are describing. I only have 89k on my 05 CTT.
it sounds to me like the torque coverter slipping. When PASM is turned off its likely keeping the torque coverter unlocked?
i have an icarscan and can see the slip ratio and torque denand to see how the torque converter locks and unlocks if you had similar you could see this abnormal behavior realtime and plot it.
have you tried it in manual mode in 3rd, so it won't shift out of 3rd. Then gently accelerate and recreate you problem, but then step down past the diwnshift click on the pedsl, this will force it to unlock the converter and feel like its shifting as the revs will rise but still be in 3rd. Maybe this transition is not happening correctly for you as it should.
When was the tranny last serviced, correct fluid, enough fluid.
sounds to me like something wrong with the torque converter or what controls it.
at least my response is consistent.
Assuming its behaving like i think you are describing, its normal torque converter operation locking and unlocking.
I have the same situation every day going up a gentle hill and avcelerating in third and do not have the problem you are describing. I only have 89k on my 05 CTT.
it sounds to me like the torque coverter slipping. When PASM is turned off its likely keeping the torque coverter unlocked?
i have an icarscan and can see the slip ratio and torque denand to see how the torque converter locks and unlocks if you had similar you could see this abnormal behavior realtime and plot it.
have you tried it in manual mode in 3rd, so it won't shift out of 3rd. Then gently accelerate and recreate you problem, but then step down past the diwnshift click on the pedsl, this will force it to unlock the converter and feel like its shifting as the revs will rise but still be in 3rd. Maybe this transition is not happening correctly for you as it should.
When was the tranny last serviced, correct fluid, enough fluid.
sounds to me like something wrong with the torque converter or what controls it.
Last edited by Corvetteboy6988; 01-28-2023 at 07:28 PM.
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