No longer available new These orifices are used to restrict the QUANTITY of vacuum being delivered to the vacuum control shift valve (VCV). This is the valve on top of the injection pump that sends the proper vacuum signal to the transmission modulator. Larger size orifices can soften the shifts and smaller size will normally make shifting more firm. This of course depends on the condition of the vehicles vacuum system, proper VCV adjustment, and correct modulating pressure in the transmission.
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Complete instructions are included in my manual "61x Diesel Automatic Transmission Tuning for Peak Performance." SEE related products below to order.
You can spot the location of the original orifice by looking for a colored band between the hose connections near the VCV. These modified orifices can be placed in the small location and they go in nice and tight so they will not leak or come off (even better than the originals because they have a barb on the end).
Related Products:
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.