1992 300 2.6 transmission slippage

Out of nowhere it started to slip...my local mechanic put in some transmission sealer and SLIPPAGE stuff...it worked fine then started to slip now it is working OK again. Anyone experience this? i love my car
and it is in immaculate shape but has a transmission problem...HELP
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It slips because its clutches are not tight enough. That's because they're either worn out or there's insufficient hydraulic pressure. Low pressure can result from a worn out pump, fluid that's so old that it's now like syrup or overfilled fluid that's being aerated by the gears.
Your message lacks mileage, last fluid change and when the slippage occurs, put these facts on the table and someone may be able to help you.
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Thanks TG for your swift reply. here's the story. Mercedes 300E 1992 auto trans 2.6 engine great condition 111,000 miles. I drove from LA to San Fran (8 hours straight) found brownish fluid under my car mixed in with AC condensation. Mechanic I found in a foreign car place (done biz with before seemed honest) sez it is coolant with a stop leak thats why it is brownish. By the way sez he i think I'd replace those trans cooling hoses (2)I think he said he saw a slight leak. I agree because he's the mechanic I'm not in his biz. He replaces two hoses at $43.00 apiece PLUS puts in ATF Fluid, Auto Transmission, MERCON qty 0.25 (I'm reading from the bill in front of me).and i see here he adds a non-chlorinated cleaner why...I don't have a clue but i suspect this is not good.......quantity 0.30 I drive back from SF to LA at 70+ MPH no problem. I put on 733 miles since i had these repairs. Yesterday the trans slips after it drove perfectly....engine revs 1st gear only slight...this never happened before. I go to my local guy who I (somewhat) trust...he puts in a sealer/slip trans fluid...it works fine for 8 miles.. I feel slipping...then it goes back to no slipping. Today it works fine. My local guy sez the o-ring is leaking and the fluid he put in will expand the ring...could be a solution or could be a big problem if this fluid does not work. He adds... Sorry for the long note. If you have the patients...here what the receipt sez"remove transmission cooling line, clean the leak area, start engine and run trans through the gears, inspect for leaks. all good, reinstall cover. T.G. Lambach wrote:

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OK. The motor had / has a coolant leak so the transmission's cooling hoses were replaced.
For future reference the transmission fluid is circulated to the lower radiator tank (the cool one) to be cooled and returned to the transmission.
What about the engine's coolant leak? No mention of it being fixed.
Anyway, IMHO the first thing YOU should do is check the transmission fluid. That's done after some driving, say 5 + miles, engine idling transmission in Park and the car parked on a level site. The correct level is BETWEEN the two notches on the transmission dip stick. Over fill is as bad as under fill, should be BETWEEN.
That said, you should know that when the motor is cold the transmission's first shifts are deliberately delayed to keep the motor at high rpm; that's done to quickly heat up the exhaust catalysts. So don't confuse this design feature with transmission slippage.
At 111K miles this transmission should be as smooth as a silk stocking. If you are in doubt, have the fluid changed, including draining the torque converter and changing the filter. Then leave it alone.
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