Ml 270 CDI transmission not shifting when warm

[Tsiou]

Hello to everyone in the forum, when I drive for more than 100 kilometers or go up a mountain road or any other scenario that puts the transmission under load I start getting very delayed shifts and in the end it only shifts at the limit almost 4500rpm. The tiptronic can be used to force it to shift but in the end this stops working aswell. The transmission connector has been replaced it has mercedes official ATF and filter. It was scanned by 2 mercedes dealerships absolutely zero errors or codes. when the ATF was changed there were a few small metal particles inside but I believe in a transmission with 340k kilometers some metal is to be expected and doesn't necessarily mean catastrophic failure. I have also used Lucas oil transmission fix no difference. I can't find anyone with this problem on the internet It feels like my trans goes to another "map" and shifts up late and downshifts aggressively to keep the revs high like I am on a track . I am all out of ideas I think some radiator or hose is clogged and can't circulate fluid properly causing overheat and TCU tries to keep revs high to spin the pump and cool the trans. Finally I should mention that there is no slippage no harsh shifting or weird clunking noises nothing that indicates that something is wrong with the transmission. You can put your foot to the floor and it will do 0-100 in less than 11 seconds most of the time so better than factory spec. Thanks to anyone who reads it all and sorry for the long text

 

[Tsiou]

TLDR:
transmission upshifts latet and later if the car is stressed or driven for a big distance, no codes or errors no slippage no harsh shifting no weird sounds .oil is changed to official merc ATF .

 

[Dodipops]

Get a full scan done for engine, trans and abs fault codes. That’ll give a better clue.

 

[mersum1es]

Ask them to investigate what happens when fault is on

 

[DSM10000]

Check the transmission fluid level is correct, too high a level can be as bad as too low and that the transmission oil cooler isn't blocked.

 

[mersum1es]

Too high transmission oil temp begins to drop gears off one by one, starting from highest gear. BUT that should trigger a code, now IF your dealership knows what tahey are doing, and its is 100% true there is no codes, car thinks everything is ok. Then its something which effects to gear change event, like said from transmission on engine side.

Edit: Engine is not remapped?

 

[13enzy]

Check the transmission fluid level is correct, too high a level can be as bad as too low and that the transmission oil cooler isn't blocked.

Hi
where is the transmission oil cooler
and how do check my transmission oil correctly (engine hot & cold)
Mercedes ML 270 cdi Auto 2002 (UK)
Thanks

 

[13enzy]

Too high transmission oil temp begins to drop gears off one by one, starting from highest gear. BUT that should trigger a code, now IF your dealership knows what tahey are doing, and its is 100% true there is no codes, car thinks everything is ok. Then its something which effects to gear change event, like said from transmission on engine side.

Edit: Engine is not remapped?

Hi
what could be the problem as "Transmission on engine side" etc ?
Thanks

 

[mersum1es]

Engine data is affecting how transmission is controlled. So if there is something weird happening in engine side (or faulty data), that will cause transmission to misbehave.

 

[Tsiou]

Ask them to investigate what happens when fault is on

Its not really a fault if driven at 50-60 kph or left to cool down it slowly goes back to normal within 5-10 minutes and this behaviour is sadly only occuring at summer at 30-35Celsius outside temperature so I can't troubleshoot properly.

 

[Tsiou]

The car was sitting unprotected for 10 years prior to that and the ATF was unchanged for at least 100k kilometers so maybe some radiator or heat exchanger is clogged unless the pump on the trans is destroyed and can't circulate the fluid

 

[DSM10000]

The car was sitting unprotected for 10 years prior to that and the ATF was unchanged for at least 100k kilometers so maybe some radiator or heat exchanger is clogged unless the pump on the trans is destroyed and can't circulate the fluid

If the fluid wasn't circulating you wouldn't have drive or gear engagement.