i recently bought a 97 e420 (month or so ago) with 150k miles on it, and i initially noticed no problems. few days ago on a cold morning (27F) the car started normally i took a short trip and on my way back the transmission got stuck on third gear and would not upshift no mattet how much i revved it. I tried to manually shift the car or put it on N and back on D. it did go to neutral but when back on D it stayed on third gear. i stopped the car, turned off the ignition and turned it back on and it shifted fine. well if that wasn't weird enough, the next morning (just as cold) i drove the car and i noticed that the shift knob was hard to shift between D and 4, before it needed only a simple nudge. then after about 30 minuted of driving it would become significantly easier to move. the transmission was shifting fine at all gears though. i remenberd that that had happened the day before too. also on that same day when trying to back up the knob got stuck and it would not engage in reverse (it would move to the reverse position or park but would not engage). the car was still engaged in drive. then i forced the knob back to drive and i heard a pop originating from the top of the trans (no internally i think). from then on i could shift the trans in all positions and it engaged normally. So here is my delema! WHAT THE HECK IS HAPPENING TO MY CAR! i drove the car this morning and it drove fine, temperatures where in the high 40's. I'am speculating the the AT fluid is in desperate need to be changed. i don't have the updated service records for the car, so i don't know if the trans has been serviced before. any ideas! your help is greatly appreciated .

Check your ATF fluid. What I do is get a white rag, with no crap on it, and get a drop of the fluid from your car on it. Then I put a drop of new fluid next to it... If theyre the same, good, if not change the fluid and filter... BUT I'm not sure thats the problem, but you should change it anyways if you dont know the records.

~Nate

i checked the fluid today, i didn't have the dipstick so i went to home depot and bough a length to steel cable and it went in perfect. i was surprised to see that the fluid looked clean. it had a yellow brownish color. i couldn't verify if it had any metal shavings int it. it smelled funny but i don't have the new fuid yet to compare it. i ordered everything i need to get an AT oil change.
i was reading through hundreds of posts on this site and others and found out that somone olse had the same problem
his turned out to be the control unit ECU . it tells the transmission when to shift (these cars have an adaptive shift alogarithm). the problem resulted when the oil leached into the board shorting it out. it seems to be a common problems among V8's equiped with the five speed transmisson.
does anyone know where this board is located. and is there any way to fix it without having to replace the board and harness!?

Questions
-is the board salvagable once it malfunctions? i.e can i use a degreaser like acetone or something to dry the board.
-does the harness have to be replaced: can AT fluid leak through the thick insulation and short the wires?
-where can i obtain the board from? and does anyone have a part nummber.
-is this a do it yourslef project or should i leave it to the pro's
-would a malfuntion of the ecu board cause the transmission to break and how would i know if the trans is damaged.

i know i'm asking a lot of question but i trust that you guys are very helpful and you wouldn't mind me doing so.
any feedbak would be great.

change the fluid and filter. find a dipstick for your car. make sure the fluid level is correct.

with out a dipstick you wont know anything. starting to take mechanical things apart will just waste money. do the basics first. 80% chance this will solve your problem.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I am no MB expert, but yellow brown trans fluid? I'm from the old school and yellow brown was not good back then. I agree as stated above change fluid and filter. But also the first thing that came to my mind, was ice build up under car restricting the trans linkage. Just a thought. Good luck

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Stable:
1973 450sl
1978 red diamond ice vette
1975 steel blue convertable vette
2002 steel blue dakota quad.