So not a diesel but a shared transmission. Picked up a 06 e350 4matic from family with the 722.6 with 108k. All maintenance had been done at the dealer. Trans fluid was serviced once prior at around the 40 to 50k mark. Car was used primarily stop and go city driving. First thing I did was check for any pending codes and it was clear. Shortly after i took ownership i changed the oil and trans fluid. Used maxlife fluid rated for the nag1. Did a new filter, gasket did change the harness plug. Did not see at leaks. Fluid wasn't burnt but pretty dirty, no where as bad as some fluid swaps ive done on some Cherokees. I didn't think much of it, filled to level and drain pan twice before dropping the pan and changing the filter. Afterwards the shifting seemed slightly more crisp.

Fast forward to Friday maybe 1k since service, the wife tells me that trans is slipping and it went into limp mode. Pulled the codes and see a intake flap code and p2500. I immediately start googling and see reference to leaking harness plug. So I pulled the plug and it spits fluid. Ordered a new plug on amazon, arrived on Sunday. Pulled the plug on the pan to check the fluid. Around a 1/2qt low still dark red and no burnt smell. Replaced the plug after flushing the connector and plug. Ran the trans reset sequence and took it for a spin. Wasnt slipping under normal accel, but pushing it 3/4 throttle i could see it start to slip around 4k.

Not really sure the path take, seeing some threads saying replace the conductor plate. Other saying fluid flush and cleaning tcm( guess fluid wicks into it) Others saying trans is toast.

Chec for ATF in the transmission control module. Clean off any fluid with electronic parts cleaner.

Whether or not there are displayed codes, check for, note and delete codes at the module level, not just generic scanner codes.

That might sort it or buy time to make an informed decision.

Sixto
98 E320s sedan and wagon

I was reading there is likely more codes, so i ordered an isoft mb code reader to see deeper at the trans codes. As of right now the p2500 is just through a bluetooth scanner running the phone app torque.

so the isoft scanner arrived. I am a little boggled how many systems they car has. No additional trans codes stored. But was able to clear the p2500. Will have to see how it is after a few days. Going to spray the tcm module also.

What do you consider "slipping" ?

What is the code description for what you posted ?

Fluid normally gets dark on these due to clutch material and dye degrading. I've pulled apart high mile / original filter units that had perfect friction material. ( One had a thrust washer fail due to long term wear and the other cracked case from a crash / scrap yard pile. )

Code P2500 proper indicates the transmission has impermissible transmission ratio

In sport mode under heavy accel the engine rpm is sort of sitting a little to long between gears. Before hand the rpm was steady like a clock climbing up the tach, nice clean crisp stopping points. Engine sound matched what you could see. Now under heavy accel while warm you can see it not moving together, little out of sequence.

I know the long life reputation of these trans so i'm a bit suprised, nothing crazy about the fluid when i changed it. I have done several flushs and shift kits in other cars and what i saw in the pan did not seem out of the ordinary.

That isn't slipping. Slipping is when the engine revs up ( actual RPM not engine sound ) but there isn't any change in road speed. Sport mode will make for higher engine RPM before a shift occurs.

If an engine is down on power, generally it will hang at high RPM before a shift. The intake flap will affect low or high RPM power depending on where it is stuck.

I'd pull the TCM, look for oil and clean if needed. Oil is an insulator, but graphite from friction material is conductive and will cause issues in the TCM.

In theory, if the wheel speed sensors are erratic, it might cause a trans ratio error issue but I'd expect an ABS fault also.

The conductor plate ( actually the input / output speed sensors ) could be failing. Past that, a trans guy needs to look at it.

I know what a trans is doing when slipping and this is slipping. Hench the limp mode. I have module pulled and didn't notice any sepage.Will probably just drive it more and see if the slipping continues or the plug getting wet cleaned will solve it. With the better scanner i way able to clear the code. With the price of used parts on these and since i have a lift its not worth wasting much time on fixing it. If it keeps slipping and throwing a code i'll likely but a used unit and swap.

So just finished pulling and inspecting the valve body. No cracks or visible issues with the conductor plate. Installed the sonnex overlap sleeve kit on all the gears and swapped the 2-3 with the 3-4 solenoid. Initial drive seemed crisp, will have to take it out longer in the morning.