Hello everyone.
I have a gearbox from citroen c5 3hdi from 2008 and i want to ask if its possible to change hydroblock from this gearbox and put it to older model c5 2006 2hdi? Gearbox number are the same tf80sc.
Aisin gearbox hydroblock
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mickthemaverick
- Moderating Team
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- Joined: 11 May 2019, 17:56
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Re: Aisin gearbox hydroblock
You may find the answer in this thread: viewtopic.php?p=624030#p624030
I used to be indecisive, now I'm not so sure!
I used to ride on two wheels, but now I need all four!
I used to ride on two wheels, but now I need all four!
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Citrus1
- Posts: 2
- Joined: 06 Oct 2025, 19:24
Re: Aisin gearbox hydroblock
Thank you, but there is not enough information.mickthemaverick wrote: 06 Oct 2025, 20:00 You may find the answer in this thread: viewtopic.php?p=624030#p624030
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niko10977
- Posts: 4
- Joined: 01 Nov 2024, 15:28
- x 1
Re: Aisin gearbox hydroblock
Hello everyone, I’m looking for some advice regarding an issue with my transmission.
Car: Citroën C5 X7, 2.0 HDi 163 hp, RHH engine, automatic transmission Aisin TF80-SC (AM6 / BVA AT6), Euro 5. No active fault codes in the TCM and live data looks normal. ATF level is correct and checked by procedure.
The issue only appears while driving and only when slowing down. When downshifting, usually from 4→3 or 3→2, instead of a smooth shift the gearbox seems to “lose” the gear for a moment and then engages the lower gear with a noticeable jolt / harsh kick. If I brake harder (more aggressive deceleration), the issue is almost not present – shifts down normally in that case.
When the car is stationary and I shift between P-R-N-D, everything is smooth with no issues. During acceleration and upshifts, it also behaves perfectly fine, no delays, no slip. Engine runs smooth, no vibrations, no noises, no leaks, no suspension or driveshaft problems.
Diagnostics have been performed while driving, but nothing out of the ordinary shows up in the live data. All connectors to the transmission control area have been checked and appear fine.
My suspicion is that the problem is in the hydraulic control of the downshifts — possibly a sticking shift solenoid/valve inside the valve body which reacts too slowly when hydraulic pressure drops during deceleration. Could also be a minor pressure loss or delay in one of the circuits, or an early valve-body/mechatronic issue. When the car is stationary, everything looks normal because the hydraulic system is not under the same load conditions.
My questions:
1. Has anyone experienced the same symptom — harsh downshift with **no fault codes**?
2. Did replacing only the shift solenoid fix it, or did you need to replace the whole valve body?
3. Are there any specific AM6 live-data parameters to monitor during deceleration that might help diagnose this?
4. Could this be related to the torque converter lock-up control during braking?
I can provide live-data logs from DiagBox or even a video of the issue happening while driving, if needed.
Thanks in advance for any help or suggestions!
Car: Citroën C5 X7, 2.0 HDi 163 hp, RHH engine, automatic transmission Aisin TF80-SC (AM6 / BVA AT6), Euro 5. No active fault codes in the TCM and live data looks normal. ATF level is correct and checked by procedure.
The issue only appears while driving and only when slowing down. When downshifting, usually from 4→3 or 3→2, instead of a smooth shift the gearbox seems to “lose” the gear for a moment and then engages the lower gear with a noticeable jolt / harsh kick. If I brake harder (more aggressive deceleration), the issue is almost not present – shifts down normally in that case.
When the car is stationary and I shift between P-R-N-D, everything is smooth with no issues. During acceleration and upshifts, it also behaves perfectly fine, no delays, no slip. Engine runs smooth, no vibrations, no noises, no leaks, no suspension or driveshaft problems.
Diagnostics have been performed while driving, but nothing out of the ordinary shows up in the live data. All connectors to the transmission control area have been checked and appear fine.
My suspicion is that the problem is in the hydraulic control of the downshifts — possibly a sticking shift solenoid/valve inside the valve body which reacts too slowly when hydraulic pressure drops during deceleration. Could also be a minor pressure loss or delay in one of the circuits, or an early valve-body/mechatronic issue. When the car is stationary, everything looks normal because the hydraulic system is not under the same load conditions.
My questions:
1. Has anyone experienced the same symptom — harsh downshift with **no fault codes**?
2. Did replacing only the shift solenoid fix it, or did you need to replace the whole valve body?
3. Are there any specific AM6 live-data parameters to monitor during deceleration that might help diagnose this?
4. Could this be related to the torque converter lock-up control during braking?
I can provide live-data logs from DiagBox or even a video of the issue happening while driving, if needed.
Thanks in advance for any help or suggestions!
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niko10977
- Posts: 4
- Joined: 01 Nov 2024, 15:28
- x 1
Re: Aisin gearbox hydroblock
A detailed diagnostic of the Aisin TF-80SC/AM6 automatic transmission was carried out on the vehicle using Diagbox, along with road tests. It was confirmed that the TCC / lock-up clutch is operating within specifications – when locked, slip is close to zero, in “sliding” mode the values correspond to those requested by the control unit, and with the converter open the slip is as expected. No evidence of a faulty TCC was found. When reproducing the customer’s complaint (noticeable shifts/jerks on 2nd and 3rd gear when releasing the accelerator and lightly decelerating), it was established that the torque converter was in TCC OFF mode, the engaged gear remained Ratio 2/3, and the cause of the jerks was related to the operation of the B-clutch pack (B1/B2 in combination with C1) and its associated hydraulic control valves in the valve body.
The valve body was removed and disassembled; the relevant hydraulic valves and channels related to the B-pack and line pressure were cleaned, inspected and reconditioned, and the condition of the B-frictions was checked and restored where necessary. The automatic transmission fluid and filter were replaced and an adaptation procedure of the gearbox was performed. After reassembly and repair, test drives were carried out, during which the previously observed jerks on 2nd and 3rd gear when releasing the accelerator and decelerating did not reoccur. Gear changes are now smooth and the transmission behaviour is within normal limits.
The valve body was removed and disassembled; the relevant hydraulic valves and channels related to the B-pack and line pressure were cleaned, inspected and reconditioned, and the condition of the B-frictions was checked and restored where necessary. The automatic transmission fluid and filter were replaced and an adaptation procedure of the gearbox was performed. After reassembly and repair, test drives were carried out, during which the previously observed jerks on 2nd and 3rd gear when releasing the accelerator and decelerating did not reoccur. Gear changes are now smooth and the transmission behaviour is within normal limits.