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$98.00

1981 to 1995 722.3 722.4 Transmission Vacuum Modulator Valve

Only black is currently available, but it will work in all these transmissions. This is the easy-to-adjust upgraded version with the new style pin included.

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.

61x Diesel Automatic Transmission Modulating Pressure Test Kit
$75.50
Currently out of stock.

61x Diesel Automatic Transmission Modulator Pressure Test Kit

Updated 11/20/25 - Purchase revised kit with video instructions and speed adjusters listed below.

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.

$2.95

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.

On Demand Video
$6.99

Adjusting the Modulator with Kent's New Speed Adjuster - On Demand Video

For the new style modulator that fits the 1981 to 1995 722.3 and 722.4 transmissions. Make it Easy!!!

Out of years of frustration trying to adjust the modulator during a test drive, Kent came up with a better and faster way to make adjustments by just "reaching" under the car. This little device replaces the plastic cap during testing and adjustment.

$4.95

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:

$126.00
Currently out of stock.

1981 to 1991 722.3 Transmission GREEN Top Modulator - USED

Tested and holds a strong vacuum with good movement. Complete with pin as shown

Green top modulators are no longer available NLA. It is difficult even to find good used ones. Hard to believe we still have one. Kent found it hidden away in the shop the other day and fully tested it. The long pin is included and it has a good solft black rubber cap.

$74.85

1981 to 1995 722.3 722.4 Modulation Pressure Test Kit

This is a MUST DO test to prolong the life of these old transmissions. Full 30-minute video instructions with road test included. Bonus speed adjustment video included

Too much pressure and you will blow the seals. Too little pressure and you will wear out the clutch packs. Now in stock.  When installing a new vacuum modulator on your transmission, you most likely will need to adjust it. There are two ways to do this.

On Demand Video
$7.99

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
$28.50

Diesel Automatic Transmission PEAK Performance Tuning Manual by Kent Bergsma

Receive two related On-Demand videos FREE! Covers ALL Diesel Automatics from 1969-1984 220D 240D 300D 300CD 300TD 300SD

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.

$68.00
Currently out of stock.

1981 to 1985 Turbo Diesel Modulation Pressure Test Kit

11/25 Update - now upgraded to new kit with video instructions. See related products below to order

PLEASE ORDER THE UPGRADED KIT BELOW for your 1981 to 1985 turbo diesel  Mercedes.

$38.95

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.

$125.00

W123 W126 OM617 Turbo Diesel Transmission Ultimate Diagnostic and Tuning Kit

116 and 126 1978 to 1984 300SD, 1980 to 1984 123 240D and 1981 to 1985 123 Turbo 300D 300TD 300D 300CD. Does not apply to the 722.4 transmissions found in most 1985 models

INCLUDES TRANSMISSION PEAK TUNING MANUAL.  DO NOT ORDER SEPARATELY. Bonus videos included free. To properly tune your diesel transmission you will first need the know-how and then the equipment to adjust your transmission modulator and your VCV transmission shift valve.

$19.75

1981 to 1984 722.3 Transmission Pesky Leak Fix Kit

For 5-cylinder turbo diesel engined 300D 300CD 300TD and 3000SD. Tool not included ( purchase separately below).

These transmissions are now 40+ years old, and with age comes hardened o-rings and seals, leading to what I call "pesky" leaks.

On Demand Video
$14.99

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.

$39.50

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

Poor shifting. Try fixing yours. The kit includes three detailed on-demand videos to remove, test, and service the VCV, which can be purchased separately below!

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.

$142.00

1985 Turbo Diesel 300TD Wagon Transmission Bowden Cable - USED

With the 722.4 smaller transmission ONLY. Check your transmission BEFORE ordering.

ONLY ONE AVAILABLE. Very good used working Bowden cable with good plastic threads on the adjuster. No longer available new.  This will ONLY fit the 1985 transmissions with the black modulator. EASY twist install.  No instructions needed.:

On Demand Video
$8.99

Fixing 1981 to 1984 Turbo Diesel Auto Transmission Pesky Leaks - On Demand Video

Applies to W123 and W126 turbo 300D, 300CD, 300TD and 300SD

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.

On Demand Video
$12.99

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.

$9.95

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!