zorbas23x

I decided to leave a week early, to see some family in PA, on my way up, and almost going 700 miles, my Tranny started acting up. It was going into 3rd gear from 4th while I was cruising on I-95. Otherwise, its has been working fine, not slipping or banging gears in. I was wondering what could be the problem before I take it tomorrow to a mechanic.

BlackShark

Something going on with the kickdown switch?

Rich9928p

Always confirm that the A/T fluid level is within spec before suspecting anything else.

It is measured with the engine running and in neutral (on a level surface). Markings are on the side of the container for hot and cold.

zorbas23x

Kickdown switch is working fine.That was my first suspicion.As far as the a/t fluid is concerned i did change the radiator end tank about two weeks ago and when i disconnected the transmission oil cooler lines i did loose some fluid but it wasen`t that much,so i thought,and did not think any more about it.Maybe half a quart.Is the tranny so sensitive or is it something else that i am missing here.Like i said before i have no slipping or clunging and it operates fine until it is in normal operating temp and took almost three quarters of my trip from FLA to behave like this

Randy V

Model year?

Bill Ball

Is this your 90 S4? When this happened did you notice anything else, like a sense of lower power than before, like it had to downshift to maintain speed? I'm just bringing this up because when the ignition monitoring system trips, this (downshifting while cruising) is one of the side effects of the loss of power.

zorbas23x

Randy and bill it is the s4.Bill i did not fill any loss of power i was cruising on the interstate at 90 miles an hour when just like that it downshifted into 3rd gear.I called my friend and mechanic and told him about this odd behavior and he said said to me to shift into neutral while i was still moving give it some gas and throw it into D and see if that will fix the problem.And it did cure the problem until today.The car started fine and while still cold it was working fine but after driving it almost all day it started behaving the same way as it did on my way to PA so i parked it as soon as i could because i did not want to do any damage to the tranny since i dont have a clue yet as to is causing this

Charley B

The four speed auto is very sensitive to fluid level.

Bill Ball

OK, well then, if the kickdown switch is not stuck on, the kickdown solenoid is acting up. It has some o-rings that could be bad or it just may be sticking. Could be other things in the valve body, but the kickdown solenoid would be the most direct. Also, pretty easy to fix as it is mounted on the tranny case. Maybe Steve Cattaneo will see this and post advice.

When was the last time the tranny had a fluid and filter change? When stuff like this happens (things sticking in the tranny), a service may resolve it. It worked for me when I lost 1st gear downshifts a couple of year ago. All better since. The service interval is 30K miles.

Careful with mechanics - this is a Mercedes transmission, not Porsche.

zorbas23x

Just found the problem about the tranny acting up.Three weeks ago i replaced the right side radiator side tank and when i got the cooler lines off i lost some atf but did not think any thing of it.I got the car nice and hot this morning,drove it around for five or six miles then took it to a friends house that has a lift.Put it up and filled it with almost 3/4 of atf.It was in neutral engine running and the level was at the 20C.So i added atf until i got the level between the min and max space.Drove it on the highway for tweenty min.and its fine.Thanks to Bill Ball for his bulls eye guess and steering me in the right direction.See most of you at SITM

Bill Ball

Yes, these trannies are very sensitive to level. When I replaced the radiator sidetank, I lost maybe 2-4 ounces and did not replace it it right away and there were no ill-effects. You were 3/4 of a quart low, however. That's quite a bit. Enjoy SITM.