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Old 08-10-2013, 10:48 PM
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Transmission shifting

Little confused about the transmission shifting on my parents 87 300 SDL. I remember driving the car and being able to get the transmission to shift down without having to use the kickdown switch. Mind you that I have not driven the car in years but recently they had the transmission replaced and when I drive it now it seems that the only way to get it to shift down is using the kickdown switch. Am I missing something? Is there an adjustment that needs to be made? Also noticed that between 25-40 mph if the car is going up a hill that it is very sluggish. If someone can provide some insight I greatly appreciate it.

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Old 08-11-2013, 08:44 AM
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Depending on speed and how deep you press the accelerator pedal, the transmission can shift down without the kickdown. Usually the bowden wire will control the shift points. If the transmission has a economy/standard switch, and the transmission is in Economy mode, it will not shift back so easily. First check the bowden wire.

Bad vacuum can cause shifting weirdness, so next is to check the function of the vacuum system.
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Old 08-11-2013, 10:45 AM
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Quote:
Originally Posted by 87 300 SDL View Post
Little confused about the transmission shifting on my parents 87 300 SDL. I remember driving the car and being able to get the transmission to shift down without having to use the kickdown switch. Mind you that I have not driven the car in years but recently they had the transmission replaced and when I drive it now it seems that the only way to get it to shift down is using the kickdown switch. Am I missing something? Is there an adjustment that needs to be made? Also noticed that between 25-40 mph if the car is going up a hill that it is very sluggish. If someone can provide some insight I greatly appreciate it.
The general nature of most M/B transmissions (including yours) is their lack of any desire to do a part throttle downshift. They will do it, but the conditions must be "onerous".

What I mean by onerous is that the vehicle speed must be such that the engine speed has dropped well below 1500 rpm when the accelerator is pressed. In the area of 1800-2500 you'll never get the part throttle downshift unless you use the kickdown switch.

In these circumstances, that lever that sits just to the right of your right hand is your friend. You can effect a 4-3 downshift at anytime you need it without the need to use the kickdown switch. If you drive the vehicle around town in "3" (recommended), you can effect a 3-2 downshift with just a touch of the lever down one notch.

I currently drive a 300SE with a 2.47 diff and it presents special challenges in the exact same regard. It must utilize a 4-3 downshift for any acceleration and I must provide it. It also must utilize a 3-2 downshift for any serious accels from 25 mph to about 40 mph and I must provide that as well. The vehicle will sit there like the proverbial slug without my input.

There are limitations to any transmission design that is not electronically controlled and these boxes are a classic example of that. If you need the rpm's without the desire to mash the pedal, you're going to have to get them yourself.
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Old 08-11-2013, 06:55 PM
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They can be adjusted to a certain extent. Search function should yield results.
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Old 08-12-2013, 02:00 PM
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Use Your Shifter as Brian Suggests

Quote:
Originally Posted by Brian Carlton View Post
The general nature of most M/B transmissions (including yours) is their lack of any desire to do a part throttle downshift. They will do it, but the conditions must be "onerous".

What I mean by onerous is that the vehicle speed must be such that the engine speed has dropped well below 1500 rpm when the accelerator is pressed. In the area of 1800-2500 you'll never get the part throttle downshift unless you use the kickdown switch.

In these circumstances, that lever that sits just to the right of your right hand is your friend. You can effect a 4-3 downshift at anytime you need it without the need to use the kickdown switch. If you drive the vehicle around town in "3" (recommended), you can effect a 3-2 downshift with just a touch of the lever down one notch.

I currently drive a 300SE with a 2.47 diff and it presents special challenges in the exact same regard. It must utilize a 4-3 downshift for any acceleration and I must provide it. It also must utilize a 3-2 downshift for any serious accels from 25 mph to about 40 mph and I must provide that as well. The vehicle will sit there like the proverbial slug without my input.

There are limitations to any transmission design that is not electronically controlled and these boxes are a classic example of that. If you need the rpm's without the desire to mash the pedal, you're going to have to get them yourself.
Your shift lever is your friend with these SDLs. I have an SDL with a newer transmission. I worked tirelessly with the prior trans and the new one to get them to shift smoothly at slower speeds while in "D"rive. Now when in town I just use "3" and it drives like a dream. Just don't forget to put it back in "D" when you will be traveling over 55 - 60 mph.

Try it...you'll like it

P.S. When the car was new I wondered why such an expensive car had a transmission that seemed lost in the gears at lower speeds. I was told the "D" drive postion was intended for Touring and not city driving. "3" was the selection I should have been using. Heck even my F-150 truck was smooth as silk in "D" at all speeds. Go figure. None the less I got about 325K miles out of the first SDL trans and only put a rebuilt in because of a leaky pump seal and the thought that most of the internal seals were probably toast.
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Old 08-12-2013, 10:40 PM
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I agree the SDL tranny can be slow to respond but I never use the kickdown switch and rarely pull back the shift lever. I don't drive like a granny either. If these cars were absolutely unresponsive, no one would have paid whatever they cost when new.

Make sure the Bowden cable is attached to the throttle linkage. There's and adjustment nut at the engine bay end of the cable. When you pop off the socket to adjust the cable, make sure you feel tension when you tug on the socket. Shortening the cable should make the transmission more responsive including holding low gear longer. If the socket doesn't resist tugging, it might not be attached at the transmission end.

By chance are you running withou the ALDA?

Sixto
87 300D
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Old 08-14-2013, 02:15 PM
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Thank you everyone for your advice.

Sixto, I am running with ALDA which is the first thing I checked, completely clean. The other thing I suspect is a blocked line to the switchover valve.

I will try adjusting the Bowden and report back. It will probably be a while before I will get around to it, little overwhelmed with work, school, and kids.
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Old 08-14-2013, 06:06 PM
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my car does shift without the kickdown if I press the pedal in one action rapidly till about 70% - it shifts from 3 to 2 quickly and accelerates. btw my car has a 722.435 transmission. It started to behave once I had the bowden correct.

If you want to keep the boiler steaming, then use 3 - shift to D when the steam is no longer required.

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