My trans has an upshifting problem that just comes and goes. I have found that if I leave the fluid level at the cold full level when the trans is hot, that I have no problem. But if I fill it exactly to the full hot mark while hot, it starts to have a problem shifting into 4th.
Does anyone know what might be going on like foaming causing this?

And is it safe to run mt tranny with the fluid level a few millimeters down to the cold full level?

Thanks again everyone

It could be the dipstick is not going in all the way?. It is OK to operate so long as it is above the minimum level hot. Too full will cause foaming and earlt fluid oxidatin and tranny failure. Also a little water in the fluid will cause this. I suggest a drain/refill and check the old fluid for water just to be safe. The old stuff is probably oxidized in any case if it really has been foaming.

A quick test for water is to put a teaspoon fullin a aluminum muffin liner and heat it with a flame. If it crackles as it gets hot--that's water popping (just like water in cooking grease pops)

The dipstick is going in all the way and the fluid is clean and fresh. Maybe the replacement dipstick is a little different or maybe not exactly the right one? I have no problems unless I fill it exactly to the line or if I overfilled it a tiny bit.

there is a TV throttle - vavle cable that will influence your shift points. If you go down this road, mark were you started from and make small adjustments. It will change the full spectrum of your shifting from early to late pending weither you shorten or crank length into the cable. It will not cure your 4th gear without change 1,2 and 3. There is a given pressure for were the tranny shifts. I doubt you have a guage or know were to bolt it up to the tranny or know that max pressure limit so be sure you know were you started from. Myt car came from the factory as a late shifter or slow kick down for around town. When I went to 3/4 throttle I was always waiting for it to down shift and it would not unless I floored it. That was stupid for around town driving. Changing the TV cable gave my 300-E proper shifting manners.

Blairbuc:

Are you referring to the kickdown cable? It is adjusted correctly. I have no shifting problems other than the 3-4 if I have it full to the line and get it really hot. I drive in the mountains almost every weekend and thats where I have the problem show up. No problems though if I just keep the fluid down a few millimeters from hot full.

BTW
The fluid is fresh and clean.

Does that mean it won't shift into fourth gear or shifts somehow poorly?

__________________
2012 E350
2006 Callaway SC560

MBZ OZ

Yea what I call the TV cable is what you call the kick down cable.

But if I fill it exactly to the full hot mark while hot, it starts to have a problem shifting into 4th.
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Does that mean it won't shift into fourth gear or shifts somehow poorly?


Yes. When it happens, it will not shift into 4th. Not manually or at any RPM.

But it is fine again. Shifts and drives excellent. Definitely no slipping, shuttering, or noises. Maybe my vent is plugged?
I'll have to locate and see. Usually happens after drive up in the mountains.

I am planning on a rebuilt trans in the spring.