AM6C Gear Shift Issues

11 Comments12 January 2017  |  Stu

Affecting: C4 & Picasso C5 C6 C8 307 308 3008 407 508 5008 607 & 807

Specifically the vehicles above equipped with the AM6C Automatic transmission

The AM6 box is generally considered a good transmission. But, they can have issues with the solenoids and valve bodies, usually when they get older (150,000 km +) which requires the valve body to be replaced (they wear out internally due to the housing being aluminium which causes fluid bypass). This often doesn't produce fault codes, and tends to be worse when hot They may produce a number of shifting issues but usually don't cause the ecu to veg out or drop into a limp-home mode.

If the Sport and or snow-mode lights are flashing this is generally not a good sign, and indicates a major problem. Ideally factory diagnostic software like DIAGBOX or LEXIA should be utilised to interrogate the ECU for fault codes. Generic test equipment is usually unable to delve deep enough into the system to be of any useIf the transmission is unhappy enough about the engine sensors to go limp mode then it will log 'remote' codes in the transmission ECU declaring its disapproval.

These boxes are sensitive to fluid condition -gear shifts are much better on new oil- so, if it's done above 80,000 km and on it's original oil then a fluid change is in order. Be sure to use the factory specified Esso/Mobil ATF 3309 (JWS3309 spec) oil for this. Avoid modern 'super' transmission oils that claim to do everything under the sun.


Steps to diagnose:

  • Road test to experience fault.
  • Check with DIAGBOX to confirm presence/absence of codes, check live data for excessive fluid pressure fluctuations etc.
  • Given it seems to fault predictably, road test with diagbox running to check/record live data when it faults.
  • Check trans fluid level/condition. Replace if at all dubious.

If there are no other indicators by this stage, prepare yourself for a likely valve body replacement. We can supply a new unit to order;

Valve Block

Peter Quirk
12 January 2019  |  0:55

2008 308 2l Hdi VIN VF34CRHRJ55187745
trouble with car moving from 5 to 6 gear and sometimes from 4 to 5 without manual assistance. seems the higher the revs and incline the more the car wnats to hold on to 4th . 5 to 6 rarely changes without manual assistance
no warning lights no flashing S or W
any ideas?? do u have part number for solenoids?

28 January 2019  |  22:37

The TPMS system is separate on that car as far as I know. The TPMS fault may be caused by a faulty transmitter in one of the wheels, itís even possible that the system is displaying a low or faulty pressure because one of the wheels has been swapped for the spare and the transmitter is not emitting a reading. I would recommend a diagnostic check on the TPMS and ABS computers. The tyre pressures and wheel speeds can be verified that way. You say it rarely changes to 6th gear on its own, does it ever change to 6th on its own, if so, thereís probably nothing wrong with the gearbox. Iíd still be looking along the lines of tyre wear.

12 January 2019  |  15:26

The symptom of not changing into higher gears may, surprisingly, be caused by enevenly worn or incorrect size tyres. The ecu doesnít store any fault codes and itís a rare problem but we have experienced it more than once and it was cured by replacing two tyres. Other than that, more information / diagnostic check would be required.

Peter Quirk
24 January 2019  |  19:33

Is it usyally fronts or rears Stewart that cause the issue

Peter Quirk
28 January 2019  |  22:12

mate i am now getting a TPMS fault tyre low pressure warning but pressures are fine. is it possible that the faulty sensor is talking to the auto box and causing the fault?? I only get the PRND triangle at cold start. start and check is ok. put it into gear and PRND comes up.
Disconnect battery and wait 10 min reconnect all ok again drive off.

Peter Quirk
30 January 2019  |  9:44

Hi stewart.. so new tyres solved gear change issue. On to motorway straight to 6th gear. Still getting tpms low tyre pressure warning. Have isolated to right rear. But on the way home i stoppped on off ramp then when taking off got ESP/ASR and faulty gearbox with limp mode.. any ideas?

How much are TPMS EACH?

Peter Quirk
21 January 2019  |  22:51

2008 308 XTE 2.0l HDi with AM6C.. holding 5th even on motorway will not change to 6th unless manually changed. also if accelerating a little harder will hold 4th even up to 3500rpm and wont change to 5th even when you come off accelerator. will do multiple fluid changes and advise outcome. only 70k on clock so surely not a valve body??

Peter Quirk
26 January 2019  |  0:11

ok so now i have tyre pressure low reading on central display and then the triangle transmission warning with PRND inisde sa in a transmission fault.
Tyre pressure are fine.
Do these cars 2008 308 HDi VIN VF34CRHRJ55187745 engine no 10DYVQ4005235 have direct or indirect tyre pressure sensors . If its indirect its leading to tyres and ABS sensor if its direct it looks like a sensor failure.

If i disconnect battery and leave car restarts with no faults or warning re tyre pressure. could i have cracked the abs ring??

30 January 2019  |  13:15

Hi Peter, the tyre transmitters are £103.91 each (5430W0). You need a diagnostic check doing for the gearbox fault warning, could be an engine management fault as that would explain the ESP fault due to invalid information from the engine ECU.

08 October 2020  |  20:35

Greetings! I have a DS5. I have a problem with the gearbox. When I take it to "D" it gives me a car kick. I checked it with PC but it does not register any problems.I take the first gear with a strong kick as it moves the car completely. has a super kick.

The Gearbox Am6 Does Not Transmit Power to the Wheels.
14 March 2023  |  19:19

Good day,
please, would it be possible to advise you regarding the AM6/TS80SC.
The gearbox does not transmit power to the wheels. Any gear (R/D) but the car won't even move. Diagnostics showed error P0765, but after erasing it, there is no error anymore, but the car does not move.

Thanks for any advice.