Tech Tip #55: Cummins B Series Tachometers

Helpful guide to installing a tachometer in your Cummins B series Diesel

Got a Cummins B series diesel but no tach? Surprisingly, lots of these B Series come out of the factory in truck and industrial applications without tachs. Our Dr. Diesel™ says that running a diesel without a tachometer is like driving at night without headlights. Sure, you can do it, but why? So here’s the skinny:

Parts List

First, pick up the following parts from Cummins:

From a Stewart Warner dealer, you’ll need:

From a speedometer shop, buy a standard speedo cable with .104 drive ends.

Installing Your Tach

Remove the oil filler tube assembly and install the plastic drive unit on the now exposed nut in the gear cover. Install the new valve cover, gasket, filler cap, and seal ring in place of the old filler hole-less valve cover. Hook the speedo drive cable to the drive and the tach sender unit (which can be mounted anywhere). Hook the wiring up between the sending unit and the tack, remembering always that the drive ratio is 0.5:1.

Please call with any questions and of course, we stock Cummins B Series Service Manuals that can be shipped out same-day or e-mailed.

Written by Dr. Diesel

Knowledge is power. Power to build ties to engine users. To build a relationship with our customers, we share with you our 105 years of knowledge in many ways. We have this special section called “Ask Dr. Diesel™” where you can pose questions about engines, transmissions, industrial hand clutches, exhaust scrubbers, etc.