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Applicable to 114 115 116 123 and 126 Chassis, years and models listed above. Troubleshooting an annoying shift problem must first start with the vacuum modulator.
9/25 Update: Green and Red Modulators are NLA, and we have been informed that they will not be remanufactured. But, do not panic! You may have heard that you must replace your 1981 to 1995 transmission modulator with the correct color top. We have just learned that this is not necessarily true.
If your modulator is working ok, but leaking transmission fluid, you may only need to replace the inexpensive oring ( o ring ). You do have to be careful when removing the modulator from the transmission. For instructions (available separately) see related products below.
Illustrated 6 page step-by-step instructions for proper removal and installation of the modulator upgrade for the years and models noted here. Includes how-to specific details for using the new adjustment cap on the upgraded OEM modulators now available. These are installation instructions only.
In this xx-minute video, Kent will explain how to set up and use the different components in his kit (see below) to test modulation pressure in a 1981 to 1995 automatic transmission. This should be done when replacing the modulator or after rebuilding a transmission.
Hard to believe we still had one. Kent found it hidden away in the shop the other day. No long pin included. You will have to use that from your existing modulator. This red top unit came on my V8 engines during the 1980s.
NEW Genuine Mercedes Modulator Cap. Check to see if yours is cracked. Cap removal is required for modulator adjustment.
Typical old and cracked rubber cap:
When installing a new vacuum modulator on your transmission, you most likely will need to adjust it. There are two ways to do this.
I don't think there is any owner out there who has owned a 1978 to 1993 diesel automatic for any length of time and who has not had some sort of shift problem with the transmission. Maybe it was just a little jerk or a slipping shift. Maybe the rear end clunked hard when you came to a stop.
I have received so many emails on this topic that I had to sit down and write a very detailed manual over 130 pages in length! Let's face it! Diesel automatic transmissions can be troublesome, particularly those models that use vacuum to control shifts.
This unique kit will allow you to hook up a 30 in HG vacuum gauge between your vacuum control shifting valve (VCV) and your transmission modulator to test the VCV for proper function and to tune it for peak shifting performance.
INCLUDES TRANSMISSION PEAK TUNING MANUAL. DO NOT ORDER SEPARATELY
These transmissions are now 40+ years old, and with age comes hardened o-rings and seals, leading to what I call "pesky" leaks.
Maybe your non-turbo automatic shifts just a little too early or a little too late? Maybe your turbo diesel transmission jerks a little too much or flares during shifts?
Not all units are repairable. These are no longer available new. This is one of the best we have seen in recent years.
In this 17 minute instructional video Kent will walk you through removing and installation a VCV valve off the back of the injection pump and the proper way to adjust the linkage travel for best performance. A number of tips will be shared to reduce frustration and prevent problems.
The VCV valve controls the critical shifting patterns of most diesel automatic transmissions from 1978 to 1985. This includes the 1978 to 1985 300SD, the 1980 to 1985 W123 300D, 300CD and 300TD and the 1980 to 1983 240D.
ONLY ONE AVAILABLE. Very good used working Bowden cable with good plastic threads on the adjuster. No longer available new. This will not fit the 1985 transmissions with the black modulator. It comes with installation instructions and Kent's specially made removal and installation tool.
If your transmission is shifting too soon it can really rob your car of power and acceleration. If it is shifting too late it can be very loud and annoying and even affect fuel economy.
These transmissions are now 40+ years old, and with age comes hardened o-rings and seals, leading to what I call "pesky" leaks. They are not bad enough to flow on the ground, but they do leave wetness around the transmission and drips on the garage floor.
The bowden cable runs from the transmission to the throttle linkage on many Mercedes from the early 1980's up through the early mid 1990's. When this cable fails or is out of adjustment the transmission will either shift too early or too late.
I have never been impressed with the rubber vacuum hose found on older Mercedes diesels. I don't think the engineers ever anticipated how much abuse or how long these hoses would need to last!
Applies to 240D 300D 300CD 300TD 300SD Diesel This guide is written specifically for owners of 123 and 126 diesels from 1977 up to 1984. There are some sections that apply to the 115 and 116 chassis but it is not specific to those models.
