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Ron
Ron, ASE Certified Technician
Category: Transmissions
Satisfied Customers: 33439
Experience:  35 years working on Ford, Lincolns and Mercs.
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When shfting to 4th or drive (5th), it slips at first, then

Customer Question

when shfting to 4th or drive (5th), it slips at first, then catches/ engages, but only when warm; it is fine when cold, ad it downsifts fine. it's a 2002 E 320.
Submitted: 10 months ago.
Category: Transmissions
Expert:  Ron replied 10 months ago.

Hello, my name is ***** ***** I am a professional here at Just Answer. I have noticed that your question was not getting a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.

In order to determine if the problem is electronic or an internal problem you need to start with having the computer system scanned and see if there are any fault codes setting. In most cases if its an electronic control issue there should be a fault code and or codes. If you can get this done and post back with the results we can work from there to try and get this resolved for you.

Customer: replied 10 months ago.
HI RON, THE CAR WAS TAKEN TO A MERCEDES DEALER FOR THE PROBLEM. THEY SAID IT WAS CAUSED BY TRANS FLUID WICKING UP THE HARNESS TO THE BOX IN THE BACK OF THE ENGINE COMPARTMENT, AND ONE OF THE COILS/ ENERGIZERS WAS SOMETIMES MISSING. HOWEVER, THE PLUG ON THE TRANSMISSION END OF THE HARNESS HAD BEEN REPLACED PREVIOUSLY, AND THE SMALL AMOUNT OF FLUID IN THE CONTROL UNIT COMPARTMENT, AND ON THE BOARD, WAS CLEANED WITH ELECTRIC PARTS CLEANER, ALL OF WHICH WORK HAD NO EFFECT. A BOTTLE OF LUCAS TRANS FLUID STABILIZER SEEMED TO RESULT IN A SLIGHT IMPROVEMENT, FOR A SHORT TIME. THE FACT THAT IT DOWNSHIFTS FINE WHEN GOING UP A HILL SEEMS LIKE THERE IS HOPE THAT IT MAY NOT BE INTERNAL SEALS? HOWEVER, THE FACT THAT IT IS FINE WHEN COLD SEEMS TO INDICATE FLUID BEING WARMER AND THINNER, I.E., SEALS, MAY BE THE PROBLEM. THANKS, ***** *****PER
Expert:  Ron replied 10 months ago.

I would agree, if it seems to be fine once it warms up would usually indicate the seals swelling up after they warm up and sealing tighter. You may just want to let the condiationer work a little longer and see if it will soften the seals up enough to clear the problem. Its worth a shot.

Customer: replied 10 months ago.
IT IS NOT FINE ONCE IT WARMS UP, AS YOUR ANSWER STATES. MY QUESTION STATED THAT IT IS FINE WHEN IT IS COLD, AND SLIPS WHEN SHIFTING AFTER BEING WARMED UP, AND THEREFORE PERHAPS THE WARMER FLUID IS THINNER AND LEAKS AROUND SEALS. HOWEVER, THE SEALS MAY NOT BE THE PROBLEM BECAUSE IT DOWNSHIFTS FINE EVEN WHEN WARMED UP.
Expert:  Ron replied 10 months ago.

Okay then that would usually indicate a drop in pressure once its warm. In most cases if its an electronic control issue the computer will pick up and set a fault code and or codes. Are you getting any fault codes?

Customer: replied 10 months ago.
THE DEALER'S DIAGNOSIS DID NOT PICK UP ANY FAULT CODES. THEY ONLY SAID IT WAS THE FLUID WICKING UP THE HARNESS PROBLEM, WHICH DOES NOT SEEM BELIEVABLE. IT DOES SEEM LOGICAL THAT THERE MAY BE A DROP IN PRESSURE, BUT THE REAL QUESTION IS WHY WOULD IT DOWNSHIFT FINE, BY ITSELF, WHEN GOING UP A STEEP HILL? THUS, THE QUESTION IS: WHY WOULDN'T THE POSSIBLE DROP IN PRESSURE PROBLEM HAVE ANY EFFECT ON A DOWNSHIFT, LIKE FROM DRIVE (5TH), TO 4TH?
Expert:  Ron replied 10 months ago.

Unfortunately I do not think Im going to be able to diagnose this on line for you and its going to need some hands on testing to determine the cause. I can open the post back up for you in hopes some one else has something new to offer if you would like.

Customer: replied 10 months ago.
PLEASE "OPEN THE POST BACK UP...IN HOPES SOMEONE ELSE HAS SOMETHING NEW TO OFFER".
IT WAS SUGGESTED THAT IT COULD BE SEALS IN ACTUATOR PISTONS, BUT IT SEEMS ODD THAT IT WOULD DOWNSHIFT FINE.
THANKS,
D.