Hello all,

A new thread for a different issue since seemingly correcting the last fault.
Im recently having an issue with the car up shifting through the gears, 50% of the time its faultless and smooth the rest of the time once in 2nd gear it may hold the gears a little too long while making its way up to 5th, not always the same gears or all the gears it could be any gear at any time, sometimes i have to get revs to 3K or above to get it to up shift when it generally does it around 2k, doesn't really make any difference if im in sport or normal.
The car has a huge service history and i bought it around 3 month ago, since having it ive fixed the 2 upstream 02 sensors as they had codes pending that are now gone, new spark plugs, replaced a faulty coil pack, replaced an old fuel filter that was on the wrong way, fixed a big vacuum leak.
as i say the car has a huge service history and has been well maintained through most of its life with lots of money and part replaced throughout, but one thing I cannot see in any of the history is anything done on the gearbox.
I know they are the sealed for life box but from my understanding from the research if you want it to last it will require some tlc like the rest of the car, could my up shifting problem be a sign of low fuid in the transmission that may need a top up, or possibly changing the filter and topping up the fluid is the better route, has any one else had these up sifting issues that they have resolved or can anyone point me in the right direction of what to try next.
Many Thanks

 

Do you have a loss of power? Or does it perform normally? If there's a loss of power it might be your torque converter getting worn... If your gearbox hasn't been maintained before and you decide to do a fluid change: beware of the mudslide as a new oil will clean all and you might end up with the necessity of redoing the unit after it clogged. I'm in the middle of that so I'm speaking from fresh experience... Mudslide killed the torque converter and the solenoids...

 

I still have all the power and it goes well, I watched a video showing that the kickdown switch can hold it in gears and prevent up shift so I'm going to give that a little clean, also I've seen some videos on resetting the gearbox so I'm just going to try these out today.
Yes I am I little worried about the fluid change, please update me on how yours goes.

 

Well the gearbox reset and kickdown switch clean didn't do anything noticable, so while out I bought a 1 litre bottle of transmission fluid for this gearbox and put around 4 to 5 tablespoons down the dipstick pipe, I didn't want to put anymore in as I dont know the level of fluid inside so il buy a dipstick for this, I did notice a difference straight away as went through the gears up to 5th better, not perfect but better, that's why I only put a small amount in so if there was a difference I'd notice it with out effecting the transmission too much or damaging it.
I'm wondering if the fluid level has dropped just slightly over the years and only now is starting to effect it, I cant see any major leaks but il put a pic up of the underside of the transmission and I think you can see a that it may have leaked ever so slowly.
il change the filter and fluid then change it again after doing some miles in it to flush through the transmission. do you think the underpan has been slowly leaking from this picture?

 

I've had a look under the car today which isn't easy on the jag Jack and the car being lowered slightly, its definitely got a leak I need to get sorted, so I added more transmission fluid to see if it would make any improvements to the tiny amount I added yesterday, and it did improve very much.
so I'm thinking that the fluid is low I just dont know how low, I will order the new filter kit today and a dipstick and hopefully have it done before new year and il update this once it's done to see if the car is happy.

 

Probably low fluid. New transmission sump gasket to stop the leaks and filter and buy 5 quarts of transmission fluid that meet lt71141 fluid specs . I used non expensive fluid and it worked very well .

 

I know it probably won’t make a difference but, did you try doing a hard reset and seeing if conditions improve?

 

Hopefully this is now sorted.
I had a new filter and oil change with a new adapter plug as it was leaking at the plug, this seemed to improve the gearbox only slightly but still had shifting issues, tried resetting it and using the adaptive learning techniques but it didn't work.
so I ordered a new conductor plate and torque converter solenoid, another filter and the recommended mercedes oil. Once all was installed I drove it around for a few hours over 2 days manually shifting the gears to where I'd like them to change as this is what the mercedes guys told me to do so the gearbox re learns quicker after the reset, so shifting up through the gears and down through the gears as I'm slowing to a stop.
This seems to have done the trick and it's now a joy to drive again however I haven't used sport mode and probably shouldn't for a little while until I'm happy that the gearbox learning has settled in.