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  #1  
Old 11-09-2000, 03:09 PM
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Location: Vernon, CT
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I have read here that these trannys were 4 spd. and that you should feel 3 shifts. Is there an overdrive gear? I only ask because my car's gear selector reads P,R,D,S and L. That would be 3 fwd gears. Or am I missing something. My car only shifts twice 1-2, 2-3. On the highway cruising at 70 the car is turning 3k. Is this too high. The car shifts great, no problems at all. However when I read here, that the tranny should be shifting 3 times, I started to worry. I bought this car about 6 weeks ago, and thought everything was fine with the drivetrain, now I am having doubts. Any insight would be greatly appreciated.

------------------
1980 MB 300SD
1999 VW Passat Wagon

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  #2  
Old 11-09-2000, 08:09 PM
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Your model commonly looses 1st gear. It looses it because the only way you get it in drive is electrically.

The treans should be in second gear with your foot on the brake. When you remove your foot the relay kicksdown to first.

The positions D,S,L replaced the numbers 4,3, and 2. In D you should get all four gears but only with electrical kickdown do you get first. In S and L you reduce the top gear and change the shift points upward for the lower gears.

The control unit for first gear is in the right kick panel and often fails because of shorted kickdown solenoids. The same solenoid worked on other models flawlessly but there were numerous failures on 116.120 chassis. The fact that kickdown was used on every take-off probably did in the two parts, but I often see these cars running around missing a gear.

To really verify this start in L. With a full throttle you should start in first and only shift to second. Bump the shifter to S and you should shift to third and finally move the lever to D and you should get a third shift into 4th.

The only MB 3 spd autos came on the 4.5 and 6.9 V8s and the Detroit automatic used in the 300d (as in 1958).

------------------
Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician
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  #3  
Old 11-10-2000, 09:38 AM
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Location: PA
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3000 RPM is about right for 70 MPH in high gear. 4000 RPM will get you about 60 in 3rd gear. That's what I was using near Vail CO on the interstate to pass everything else on the road. The Turbo is worth its weight in gold at high altitudes.
P E H
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  #4  
Old 11-10-2000, 03:03 PM
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Location: Vernon, CT
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Steve, Thank you very much for the tech. info on my trans. I"ll have to try your method for trouble shooting the problem. Is this a part that I can still get? How difficult is it to swap out? Also, is there any problems with the car running as is?

------------------
1980 MB 300SD
1999 VW Passat Wagon
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  #5  
Old 11-10-2000, 07:10 PM
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Dear Steve,
Are the 1980 300SD's different from the 79s as far as shifting into first at take-off?. I remember my 79 stayed in second when stopped and as you pushed the gas it downshifted to first, this downshift however was contrlled by a rod connected to the throttle/transmission, not by a solenoid. Could rickjordan's problem be a rod out of adjustment? Just curious.
Thank you and best regards,
Joe Brasileiro
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  #6  
Old 11-10-2000, 07:41 PM
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The 78-80 300SD were the same. They all should have electronic kickdown. Normally adjusted, the control pressure linkage alone will not get the 1st gear downshift.

The problem most often was the relay in the right kickpanel. Every one I ever had bad was fixable by resoldering the PC board inside the relay. Sometimes the problem was caused by shorted magnets on the solenoid. Often the problem was simply a open magnet.
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  #7  
Old 11-10-2000, 07:55 PM
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Steve,
I did whatyou suggested by starting with the selector in L and flooring it. The car did indeed start off in one gear and then shifted and stayed in that gear until I bumped the selector up to S. It stayed in that gear until I bumped it into D. So this does confirm the tranny has it's 4 gears. So this kickdown solenoid is repairable or can it be purchased from somewhere? Speaking of switches and such, what is the switch that is behind/under the accelerator. It is round and looks like it would only be hit if the accelerator was pushed to the floor, like I did tonight.
Thank you again for the tips/advice.

------------------
1980 MB 300SD
1999 VW Passat Wagon
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  #8  
Old 11-10-2000, 08:47 PM
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The switch on the floor is the standard kickdown switch previously known as "passing gear". As usual, the failure in your system precludes this switch working.

To repair, I would suggest getting the wiring diagram and follow the circuits. The problem will be in the relay or the solenoid, most likely.

------------------
Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician
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  #9  
Old 11-11-2000, 04:38 PM
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When the rod from the throttle linkage to the transmission on my '80 300SD slipped off, the teansmission always started in 2nd gear unless shifted manually to L.
P E H
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  #10  
Old 11-19-2000, 03:14 AM
bisric
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I have a 116 (78 300sd) and will take a look at this.

Question - sometimes my 116 will seems to slip a little between 2 & 3rd gears. It seems that this tends to happen with moderate load on the engine. When under heavy load and light load it tends to be more normal.

This is a tranny going bad or a vaccum problem . The tranny shifts real smooth all other times.

PS - Fluid level is fine and filters are routinely changed.
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  #11  
Old 08-29-2005, 11:12 PM
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looks like my problem too

Quote:
Originally Posted by stevebfl
The switch on the floor is the standard kickdown switch previously known as "passing gear". As usual, the failure in your system precludes this switch working.

To repair, I would suggest getting the wiring diagram and follow the circuits. The problem will be in the relay or the solenoid, most likely.

------------------
Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

this just problem happened to my 1980 300sd i suspect. really slow to get up to speed. all the vacuum lines up top seem to be clear and in good shape. definatly no first gear unless i use the shifter.

can anyone help me locate the solenoid? i have found the relay as described and that seems to be working but i want to test the solenoid and am unsure where it is.

thanks.
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  #12  
Old 11-06-2019, 11:02 PM
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Join Date: Jan 2007
Posts: 36
The 300d was different that the 300sd. The 300d would in fact engage first gear the moment you hit the accelerator pedal and worked on vacuum. The 300sd would shift into 1st electronically after you released the brake pedal using a relay. Yeah I know this thread is at least 20 years old, but hey so is my car


Quote:
Originally Posted by jbrasile View Post
Dear Steve,
Are the 1980 300SD's different from the 79s as far as shifting into first at take-off?. I remember my 79 stayed in second when stopped and as you pushed the gas it downshifted to first, this downshift however was contrlled by a rod connected to the throttle/transmission, not by a solenoid. Could rickjordan's problem be a rod out of adjustment? Just curious.
Thank you and best regards,
Joe Brasileiro

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