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Old 11-01-2017, 09:05 AM
Fotherm Fotherm is offline
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Join Date: Sep 2014
Location: warwick
Car: C Class / 2006/ 3000
Posts: 5
Default Automatic Gear Change

Grateful if anyone could advise on the recent problem my C320 has developed - occassionally the car will not go into the next gear at around 50 mph. If I switch off the engine the problem is resolved. Any advice welcomed
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Old 11-01-2017, 10:17 AM
Flyinspanner Flyinspanner is offline
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Join Date: Aug 2010
Location: Ruislip
Car: CL500 -W215, A140-W168
Posts: 408

How many miles has it done?

Is the transmission fluid at correct level?
How does fluid look? (Hopefully cherry red, sweet smelling)

If brownish or smells 'burnt' then you may well need a fluid change (has it ever been done in the past?)

If looks n smells ok, then get a STAR diagnosis.

If it feels sluggish and won't change up or down, (have you tried 'manually'- tapping selector sideways) then it may be the speed sensor on the gearbox electric 'plate' - it would be around 400 at an Indy inc trans fluid & filter.
Stick back, houses small.....stick fwd, houses big!

Last edited by Flyinspanner; 11-01-2017 at 10:20 AM.
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Old 11-01-2017, 12:24 PM
umblecumbuz umblecumbuz is offline
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Join Date: Sep 2010
Location: Wales and Gozo
Car: S204 cdi, C220cdi 2005. C 270cdi (gone and regretted), SLK 3.2 (ditto), other non-Merc machines
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Check fluid level before doing anything elee.
If it hasn't been regularly serviced, this is the obvious first step.

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Old 12-01-2017, 09:32 AM
Steve@Avantgarde Steve@Avantgarde is offline
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Join Date: Dec 2009
Location: Bristol/Somerset
Car: Mercedes-Benz C32AMG and SLR Coupe 2005.
Posts: 5,050

Valve in the valve body is sticking or the speed sensor on the TCU is filthy so it cannot read a permissible speed ratio.

You can try removing it, cleaning it and flushing the ATF, if it still happens after that then a new TCU will be required.
Avantgarde Automotive, Unit 14 Hither Green Trading Estate, Clevedon, North Somerset, BS21 6XU
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