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1997 SLK230
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17 Posts
Discussion Starter #1
My 1997 SLK230 with a 722.6 transmission (190.000km) is still going strong. Had a transmission conductor plate change around 8 years ago (speed sensor issue) and around 2 years ago applied a Transgo kit (new design pressure regulator and change of all springs) and Sonnax o-ringed sleeves to the valve body to fix some flaring issues. Everything was fine for a while but recently I've been having hesitation on the 2-3 shift when the engine/transmission is relatively cold (20C). It just won't shift for some time - the engine RPM goes higher than normal and starts to hold back when the shift should happen, but it takes 30 seconds or more for it to finally shift. Strange thing is that after this one hesitating shift, the gearbox then shifts normally for the remainder of the drive, until I park the car again for >4hours. My gearbox is running on 236.14 spec'd Febo fluid.

I'm totally puzzled if this is a stuck solenoid (or leaking solenoid o-ring) or an issue with the fluid pump (in the torque convertor). The moment the transmission is at 80C, all problems disappear and it shifts like a charm. But this cold first 2-3 shift is annoying the hell out of me... Note: the 1-2 shift is fine when cold.

I'm very curious if anyone encountered a similar issue or has any idea. Thanks!
 

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Registered
1998 , SLK 230
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247 Posts
Is this a different issue from the way the control system holds the gears down/revs up until the exhaust cats heat up?
 

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Registered
1997 SLK230
Joined
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17 Posts
Discussion Starter #3
Is this a different issue from the way the control system holds the gears down/revs up until the exhaust cats heat up?
Thanks for your answer, but yes, the control system will make the gearbox rev up higher when cold to achieve operational temperature faster, but when reaching higher speeds it will move to the next gear. My car currently (and only recently) is really hitting high rpm (~4000) and then the gearbox is trying to shift but it just seems “stuck” and starts limiting the rpm from going up further making the car hesitating and only after around 30~60 seconds it will finally switch gears. This is new behaviour to me and I’ve been driving this car for 12 years now. But I’m really puzzled what the root cause could be.
 
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