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123 126 124 Chassis with 722.4x Transmission - Upgraded BLACK Modulator Valve

Fits late 1985 123 and other models listed in description from 1986 to 1993 - Check the color match

If you are experiencing very hard or less than perfect shifts, a failed transmission modulator could be the problem. New Genuine Mercedes part. This unit is an upgrade over the original. It has a better thrust pin design which is less prone to cause pressure variations in cold weather.


123 107 126 201 124 722.3x and 722.4x Transmission Modulator O-ring Seal

For re-sealing green and black modulators on most 1981 to 1993 models.

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.


W116 and W107 722.1x Creme Body Automatic Transmission Vacuum Modulator - USED

Fits most 116 1978 to 1980 300SD, 450SE /L and Late 107 450SL Be sure to confirm a color match to existing . CHECK BEFORE YOU ORDER! Yours must look exactly the same.

 This is a good used original genuine transmission vacuum modulator valve with adjustment key and cap. Failure of this part can lead to harsh or jerking shifts and in some cases prevent the transmission from shifting into 4th gear.


1980 and 1981 NON Turbo 300D, 300CD Transmission Red Modulator - USED

No longer available new - super hard to find and a must for shifting of these transmissions! - may fit some 1980 -81 240D

This was a new replacement unit only on the car for two years. RED MEANS RED. Only works if your current transmission has a red modulator THAT LOOKS EXACTLY LIKE THIS ONE. Will also work on some 80-81 W123 240's.  Kent installed a new cap o-ring and thoroughly bench tested this unit.


Transmission Modulator Valve Rubber Cap

Fits Late 123 107 126 201 and 124 Chassis 1981 to 1993

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:

On Demand Video

Troubleshooting Older Diesel Automatic Transmission Shift Problems - On Demand Video

Knowing where each component is located and what it does is the start of solving externally caused shift problems

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.

61x Diesel Automatic Transmission Tuning Manual

Diesel Automatic Transmission PEAK Performance Tuning Manual by Kent Bergsma

Receive a Related Bonus-Product FREE! Covers ALL Diesel Automatics from 1969-1984 220D 240D 300D 300CD 300TD 300SD

Lets face it! Diesel automatic transmissions can be troublesome, particularly those models that use vacuum to control shifts. This is largely due to the fact that diesel engines don't produce vacuum naturally. It has to be artificially manufactured.


Diesel Automatic Transmission VCV Vacuum Controls Testing Kit

All diesel Automatic Transmissions with Vacuum Modulator Fitted 1978 to 1993

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.

Currently out of stock.

1980 to 1984 Diesel Transmission Vacuum Shifting Valve ( VCV ) - REBUILT

Very hard to find ones now that are even rebuildable. LAST ONE available. Critical for proper transmission shifts non 1980 to 1985 240D 300D 300CD 300TD - 1981 to 1985 300SD. Free video instructions included.

Not all units are rebuildable. These are no longer available new. This has been rebuilt and tested in our shop and is in good working condition. When you put it on your particular diesel it most likely will need to be adjusted.

On Demand Video

Diesel VCV Valve Installation and Linkage Adjustment Instructions - On Demand Video

Applies to OM617 Turbo Diesels from 1978 to 1985 and OM616 and OM617 Non Turbo engines 1980 to 1983

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.


Engine and Vacuum System Troubleshooting Gauge

Small and inexpensive gauge to have in your tool box. Reads 0-30 inches of vacuum. 12 inch vacuum hose attached

This is the same guage that we include in two other kits. See related products below. We realize some may just want a simple vacuum gauge to have in their tool box for troubleshooting purposes. A gauge like this is a "must have" if you are having vacuum related problems on your older Mercedes.


1978 to 1985 Diesel VCV ( Vacuum Control Valve ) Internal Inspection and Service Kit

We can not call this a rebuild kit because not all VCV valves are repairable. Comes with 3 detailed On-demand videos to remove, test, and service!

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.

Currently out of stock.

OM 617 Turbo Diesel Automatic Transmission Bowden Cable

USED CABLE ---- Fits 1981 to 1984 Turbo 300D, 300CD, 300TD and 300SD with free video instructions

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. Comes with installation instructions.

On Demand Video

Transmission Bowden Shift Control Cable Removal and Replacement - On Demand Video

Specific instructions for 1981 to 1985 Turbo Diesel Automatic Transmissions

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.


Ultimate Oil Resistant Hi-Temp Reinforced Vacuum hose - 3 FEET

For 1/8 inch vacuum hose connectors on 240D 300D 300TD 300CD 300SD

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!

Diesel Vacuum Source Troubleshooting and Repair

Diesel 616 617 Vacuum Source Troubleshooting and Repair - by Kent Bergsma

Basic manual on vacuum output and testing. Does not cover all things vacuum. See description

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.