1973 450sl roadster automatic - Mercedes-Benz Forum

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post #1 of 2 (permalink) Old 06-18-2014, 11:32 PM Thread Starter
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Date registered: Jul 2012
Vehicle: 1972 300sel 4.5 & 1973 450sl
Location: Fairfield, CA 94533
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1973 450sl roadster automatic

recently i had some work done and I can only assume that the mechanic failed to refill/top off the trans fluid. About 300 miles later my gears were hard shifting. I checked the fluid, it was real low, it took 1/2 quart or 540ml to achieve the top line after all gears were lubricated. I checked for leaks and saw a drop, but never once a drop on the floor of my garage and those 300 miles combined were only two driving occasions over an elapsed time of 4 months. After proper fluid replacement, there is still a hard shift into and out of drive. Reverse has not changed so much and is mostly smooth. I am aware of the vacuum modulator, but I have been told of adjustments that I can make to the transmission to smooth or sharpen the shift, and that the modulator has something to do with it. I am mechanically inclined, but ever so scared to turn the first wrench, then usually I am fine. I'd hate to botch things up. I could really use some advice and i hope i didn't take my perfectly running 450sl and botch it up. thanks much

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post #2 of 2 (permalink) Old 06-19-2014, 05:06 AM
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Date registered: Jun 2010
Vehicle: slc5.0cab 280sl5sp 280se4.5 500sl92 GONE:280sl79 4xW114/5 3x450sl72-3 280slc4sp81 280s69 73,81SLCs
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It might be nice if a moderator could move this to the 107 forum.

Is it hard shift into Drive, and hard shifts between 1 and 2 and 2 and 3? Or is it just a hard thunk when shifting into drive?

Vacuum leaks increase the manifold pressure just like a wide open throttle would, which causes higher revs before shifts, and that makes shifts feel hard when you aren't accelerating quickly.

I fixed some vacuum leaks in my 73 450sl and was a little disappointed that the car didn't rev as high under full throttle as it had before. It was smooth as butter though, just not as sporty.

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