My '87 300 SDL is experiencing rough shifts. The shifting is not so bad when accelerating hard, but light to mid acceleration is what causes the harsher shifting. I realize "feeling" the shift points in these cars is largely considered a feature. I do not mean harsh like good, this seems somewhat like a clunk. Additionally, the shifts appear to be more harsh when the AC is on.

Thanks.

__________________
Chris

'04 ML500 - 53k, Inspiration Edition, Desert Silver
'11 Audi A4 Avant - Brilliant Black
'87 300SDL sold
'99 C280 Sport sold
'85 190E 2.3 sold

How's your vacuum? Door locks work? engine shuts off without using the stop lever under the hood? Power brake assist OK?

When the vacuum pump was going out in our '79 300D, the vacuum modulator was not getting enougn vacuum to work properly, and low-speed, low throttle shifts were real neck-breakers.

What the car was trying to tell us was that its vacuum pump was going out. It eventually failed on the freeway one day, brakes were totally hard to apply.


After I rebuilt the vacuum pump, tranny shifted smooth as butter.

Nate Stanley
'79 300D
'84 300DT
"85 F-250 6.9L
'96 Crown Vic

It's all vacuum! It could be the 3/2 way valve on to of the motor or any number of possible vacuum leaks. Not a huge problem, just hard to pinpoint. I have replaced almost all vacuum lines on my car as a precaution/hobby with good woven vacuum hose from the MB parts dealer. $3.50/ft is money well spent. $7.00 so far...as far as vacuum pump??????

__________________
1982 300D Turbo "Helga"
380,000 miles

Thanks for the responses. All vacuum-related components are functioning properly. The vacuum pump was replaced last August due to intermittent loss of the power braking capability. Any common areas for a vacuum line problem?

__________________
Chris

'04 ML500 - 53k, Inspiration Edition, Desert Silver
'11 Audi A4 Avant - Brilliant Black
'87 300SDL sold
'99 C280 Sport sold
'85 190E 2.3 sold

Still possibly the 3/2 way valve on to of the engine. I'm not exactly sure how, but that aids in shifting and even if the vacuum lines are OK, the vavle itself could be worn. Mine did the same kind of clunking both upshifting and the last downshift before you stop. It sounded and felt like the transmission was going to jump out of the car. I went to a mechanic (before I knew about this website) and got out of it for $200. The aforementioned valve is what he replaced as well as some other adjustments which may play a part as well. Search on Bowden cable. The 3/2 way vac valve is about $72.

__________________
1982 300D Turbo "Helga"
380,000 miles

Check all your vacuum lines for cracks or separation. This has happened to my ’91 350 SDL a few times where the vacuum line that goes to the tranny has slid off causing hard shifting. (low speed shifting is a neck snapper) It usually happens after I mess around under the hood.

Mav

__________________
'91 350SDL 165K miles
Lovin' her until she blows...
'01 Dodge Ram Cummins 4X4 DWR
Stump pullin' beast...

Where is the 3/2 valve located on a 87 300SDL. I have the same shifting problem.

Thanks

__________________
Enough about me, how are you doing?

I have a 85 500SEL with 300k and when it shifts from 1-2 it clunks hard. My first thought is the tranny mount might be broken. Has anyone heard of the mounts braking or should I be looking at vacuum leaks?

Hello goldenbear
Check vacuum hose routing.
Last month we had three come in with reversed routing.
You will need the hose routing diagram to do this.

__________________
ASE Master Mechanic
asemastermechanic@juno.com

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
1984 190D
2003 Volvo V70
2002 Honda Civic

https://www.boldegoist.com/

I don't think there is one. Vacuum is routed to the throttle modulator on the side of the IP to the amplifier and temp control switch on the left wheel hump then to the transmission modulator. Check for leaks in those components.

goldenbear, did you just change oil or do work near the IP? Maybe you knocked off the vacuum line to the transmission.

Sixto
95 S420
87 300SDL

Replace all the vac line rubber connectors and verifty that all four branches on the 5-way T at the front of the engine hold vac. I found that the vac actuators for the air recirc and EGR valves were both shot, so I plugged the hoses until I get around to replacing the actuators. The leak was enough to prevent the ACC from working (only air out the defrost vents) and the tranny shifted HARD.

Plugging the lines cured them both.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

After checking and replacing (if necessary) vacuum lines and connections, another culprit might be the vacuum modulator on the transmission. Do a search for posts on servicing the modulator.

__________________
1984 300SD 326,997 miles and counting . . . No wait, my odometer is still dead

So I took my SDL into the shop for hard shifting, AC charging and too much air out of the defroster. They found a vacuum leak and fixed it. What a difference.........for about 2 hours of driving. Shifting was like a new car and the volume of air out of the center and side AC vents was at least 3 x as much.

But when driving over the weekend I noticed the air was not quite as strong and then the shifting got hard again. Strange thing is that it is intermittant. On the highway, it will occasionally act like it has full vacuum again. I looked around and did not see hoses pulled loose. I do have a couple of vacuum connectors that look a little flakey and I am going to replace them one at a time. The worst one appears to be a simple straight rubber connector right out of the vacuum pump with clamps on each end. It is cracked pretty bad.

How can I find a part # for this? I ordered some 3 and 4 way connectors that were pretty standard, but had trouble locating the 2 way. Anyone have a part # or idea where I can get?

__________________
Alan Hamm
'87 300SDL 277K Miles
'89 560 SL 68K Miles

A roll of bulk vacuum hose from domestic autoparts store works fine for less money.
Four way and three way vacuum connectors:
http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1A611LS71&year=1987&make=MB&model=300-SDL-001&category=D&part=Vacuum+Hose+Connector

If you need a vacuum hose union, go to a domestic autoparts store with a chunk of hose, they will give you what you need.

__________________
ASE Master Mechanic
asemastermechanic@juno.com

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
1984 190D
2003 Volvo V70
2002 Honda Civic

https://www.boldegoist.com/

I know diagrams have been discussed here many times. I have searched but not been able to find schematics that tell me how many connectors there and of what type so I can systemmatically replace them all. Does something like this exist?

I want the car I had for 2 hours last Friday!

__________________
Alan Hamm
'87 300SDL 277K Miles
'89 560 SL 68K Miles