Most of this information was gleaned from this thread on the Ford Truck Enthusiasts forum. I thank the guys that contributed to that thread - especially David & Jonathan who provided most of the pictures. And, thanks to Bill for the info on the F & FT trucks.
Tachometers were an option on these trucks, and came with a different speedometer & trip odometer. As the following table from the parts catalog shows, there were basically only two versions - a 6,000 RPM unit for the gasoline engines, and a 4,500 RPM unit for the diesel engines. However, within each of those there were two versions - an "enclosed" version that had a cover over the discrete electronics components, and an "open" version that had no cover over the integrated circuitry - like these:
I should point out that the stock gas tachometers work on both 6 & 8 cylinder engines. There is a terminal on the tach that when left open puts the tach in 6 cylinder mode, but when grounded puts it in 8 cylinder mode, as shown in this diagram. The 8 cylinder engine wiring harness grounds it, but a 6 cylinder harness doesn't. (You can find the diagram on Page 28 of the 1986 EVTM. Or, click on the image to have it open larger.)
The info below is good when you have the tach in your hand, meaning out of the instrument cluster. But what if it is still in the truck or still in the instrument cluster? Usually you can see the #'s on the face, and certainly the RPM range, and from the information below it looks like:
- A 6000 RPM tach with E0TF-17B316-A is a gas tach, but may be either open or enclosed
- A 4500 RPM tach with E0TF-17B316-B is a gas tach, but may be either open or enclosed
- A 4500 RPM tach with E5TF-17B316-A is a diesel tach, but may be either open or enclosed
- A 4000 RPM tach with E0TF-17B316-B is a gas tach of the open variety
- A 3500 RPM tach with no marking on the front is a diesel tach
However, since Ford used the same style dash in the big trucks (F600's to 800's), and since those engines operated at lower RPM's, there actually are other tachs around that will bolt right in and work. NumberDummy supplied this information about those tachs and, as you can see, there is a wide range of full-scale RPM. But be aware that some of those were 8-cylinder only and didn't have the 8-cylinder ground terminal.
Here are pictures of many of the tachometers from various sources to help you identify them:
This is an example of a standard E0TZ 17360-A 6000 RPM gas tach. This one is of the early "enclosed" variety, meaning that it has an enclosure around the discrete electronic components. The face says E0TF-17B316-A, and embossed on the rear is E0TF-17360-Y. But, if you leave off the "Y" and use the stamped letters you get E0TF-17360-AA. And, that's exactly what the parts catalog says the early version of E0TZ 17360-A should say.
This is a 6000 RPM tach for a gas engine, and is of the later "open" variety with no enclosure and integrated circuits. The face says E0TF-17B316-A.
This is a 4500 RPM gas tach of the "open" variety, meaning it has no outer housing and uses integrated circuits. The face says EOTF-17B316-B.
Here are pictures supplied by Jonathan/Ford F834 of a closed style (non-integrated circuit) 4500 rpm gas engine tach. It came from a 1986 F700, so he expected it to be integral circuit, but it wasn't. The engineering number is E0TF-17360-Y (cast into the plastic) and BA stamped in ink next to it. Just below the cast numbers is F191 (also in ink). The face of the tach has the engineering number E0TF-17B316-B.
Here are two examples of the 4500 RPM diesel tachs, with an early "enclosed" variety on top and the later "open" variety below. The faces of both say E5TF-17B316-A, and the rear of the enclosed version is stamped E5TF-17360-AA Y S184. That matches up to what the catalog says the early version of an E5TZ 17360-A for the 1985/6 trucks should say.
And, here's a 3500 RPM diesel tach - enclosed. It doesn't have any markings on the front of the face, although it is marked EOTF-17B316-D on the rear of the face. And the rear is embossed E0TF-17360-Y and it is stamped DA A211. So, this one is the E0TZ 17360-D and it is marked E0TF 17360-DA, and these tachs came from an 1980 and later F or FT600 - 800 diesel with the AT-540 transmission.