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Old 11-08-2002, 05:35 AM
David C Klasse's Avatar
David C Klasse David C Klasse is offline
CheFrac is Back!
Join Date: Jan 2001
Location: Mission Hills in the City of San Diego
Posts: 2,352
Downshifting; Transmission Vacuum

It seems that there is a vacuum leak of some sort (I am pretty sure) with my transmission.

I have a 1995 C280 with the 4 speed auto. Car has 130,000 miles on it, and still drives like a dream. Trans. maintenances have been performed between 10-25k miles consistently. Everything is great with the transmission, albeit the progressing Reverse engagement delay.

When accelerating from a stop, all shifts are normal.
But then if I want to speed up, the car won't downshift unless I engage kick-down.
Let me give you an exaple:
If I'm cruising along at 40 mph, and I push the gas so that the trans will downshift to 3rd gear, the transmission won't downshift (will stay accelerating in 4th gear). I will push the gas to WOT, and it still won't downshift. But if I then engage kickdown, it will downshift to 2nd gear and take off.

The kick-down is fine, it's just the vacuum pressure in the trans. If I hit the gas all the way (no kick-down) down and do it fast, it will sometimes downshift to 3rd gear properly. However, if I push it slowly, it won't downshift.

I hope this was the least bit understandable!
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1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)
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