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$84.50

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.

$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.

$3.20

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
$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.

$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.

$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.

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!