Not all units are repairable. These are no longer available new. This has been taken apart, inspected, cleaned, 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. Two instructional videos are included. One to show you how to install it and adjust the linkage rod. You will also receive a free on-demand video showing you how to test a VCV for proper operation. There could be a number of other vacuum-related issues that can cause hard or soft shifts. Troubleshooting diesel automatic shifting problems is thoroughly covered in my manual on 617 Transmission Tuning. You will also need a vacuum gauge and fittings. Do not mess with this unit until you understand how to adjust it properly. See related products for the manual and my VCV test kit.
Product Details
If you need instructions on further tuning and vacuum output adjustments, you will need Kent's VCV adjusting kit that includes the needed vacuum gauge as well as a complete tuning manual on diesel automatics. This 120+ page manual will cover other shift-related topics as well. You will also need to make sure your diesel has a strong and leak-free vacuum system for this valve to work properly. Check out Kent's Vacuum Source Troubleshooting manual. Please refer to related products for additional help.
Location of the VCV.
This is the proportional valve for controlling the vacuum to your transmission for proper shifts. This plastic unit was used on 123 and 126 chassis turbo and non-turbo diesel from 1980-1984. Note that the hole in the lever for the throttle linkage is not oblong. This is one way you can tell how long a VCV has been on the engine. (wear due to vibration).
IMPORTANT: PLEASE READ. Many are confused about how to test a VCV valve. This comes from not fully understanding the purpose of the valve or how it works. Unlike most vacuum-related components ( such as an EGR valve it is not supposed to "hold vacuum." Rather it is specifically designed to leak vacuum at a controlled rate. It is really a leak down or "bleed off" valve to reduce vacuum to the transmission during shifting.
It is also important to take into account that there are adjustments that may need to be made to the transmission in order to get the vacuum valve working properly in the system. In many cases, you will not just be able to install this on your car and expect it to work at peak performance unless you test your vacuum system and vacuum modulator to make certain those are working properly as well.
This will not fit 1978 to 1980 W116 300SD. Those VCVs had a straight arm.
Related Products:
How to Test the VCV ( Vacuum Control Valve ) for Proper Operation - On Demand Video
Kent will explain the theory of operation in simple terms, why it is so important for proper transmission shifting performance, and how to test it hooked up to the engine's vacuum system with the engine running.
Diesel Automatic Transmission PEAK Performance Tuning Manual by Kent Bergsma
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.
Diesel Automatic Transmission VCV Vacuum Controls Testing Kit
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.
123 126 Diesel Transmission Ultimate Diagnostic and Tuning Kit
INCLUDES TRANSMISSION PEAK TUNING MANUAL. DO NOT ORDER SEPARATELY
616 617 Diesel VCV Shift Control Rod and Clip
ONLY ONE LEFT. Good used activation rod and plastic clip as shown. Controls travel of vacuum control valve on the top rear of the injection pump. A plastic clip can easily break. May be some slight wear on the end of the metal rod but still usable.