4500 RPM tachometer in a 4.9L gasoline truck?

Good morning folks and Happy Sunday!

I came into possession of an instrument cluster with a tachometer which I was pretty excited about before I realized it had a lower RPM count because it was from a diesel truck. It's definitely not the correct factory configuration for my truck, but it came pretty cheap and I'd rather not spend $200 (plus shipping) on ebay. So I suppose my questions is, will the tach (and printed circuit) fit and work on my 1984 4.9 i6. I probably will not purchase one (unless it's really cheap), but I have this one so if it functions in my truck, I might just throw it in there. You know, just 'cause.



(I suppose it's obvious but, the top one the donor, bottom one is mine)

I suppose I'll throw in the backstory: I got it from a local yard that specializes in bullnoses for pretty cheap in order to take the ammeter and convert it to a voltmeter in advance of pulling off a 3G conversion. I saw the tach and figured, "why not?" I do not know the year of the donor truck, just that it was a diesel F250.

(Additional question, do you guys repaint the needles in your instrument clusters? if so, what sort of paints or markers do you recommend?)

Not sure diesel and gas clusters are compatible as the Tachometer signals come from different sources.

About needle paint, I have used the one below and it "works for me" and my amateur needs. That bottle will last me a lifetime.

Go real easy on the paint. A little bit on the brush goes a long way before you potentially cause a drip.

https://www.michaels.com/product/testors-fluorescent-enamel-paint-10226505?cm_mmc=PLASearch-_-google-_-MICH_Shopping_US_N_Craft+%26+Hobbies_N_PMAX_LocalOnly_N-_-&Kenshoo_ida=&kpid=go_cmp-18514199957_adg-_ad-__dev-c_ext-_prd-10226505&gad_source=1&gclid=CjwKCAjw7s20BhBFEiwABVIMrdjcU5Q3bgeOivcbKv-ldx5PBo_l1c7ohhMgRa4JUSMEIKvdjanE-RoCOMkQAvD_BwE

If you are looking for something more professional.. I have seen this recommended before here and I think Gary did some extensive testing
https://www.hipoparts.com/fluorescent-speedo-gauge-needle-restoration-paint/

I found the thread below helpful

https://forum.garysgaragemahal.com/Instrument-Lighting-Paint-Testing-tp52526.html

So I was going to merge the two, I was going to keep the original gauge cluster and install the tach into it with it the tach's printed circuit board. At a glance it looks physically compatible. But I don't know if the internals calculate the inputs in the same way.

The diesel tach absolutely will not work with a gas engine. I plugged one in by mistake on my I-6 truck and it shuts off the ignition instantly.

The circuit films are the same (gas vs. diesel), only the 1980 year with the green circuit film or the late F600/F700 with the electric speedometer are different.

That diesel tach for the 6.9 is fairly desirable. You might very well find someone willing to trade you a gas one for it, or be able to sell it and buy one for a gas engine.

Just as a side note, there are low rpm gas tachs from F600/F700 trucks (I am running one on my I-6) but they are very rare. The one you have with the red and yellow warning zones is definitely from a 6.9 diesel and definitely won’t work in a gas truck 😞

Thanks for this. I suspected as much but felt obligated to be sure. I'll see if I can post it somewhere and get any interest in a trade.

You could probably start with the marketplace here on the forum.

Have a look at completed auctions on eBay for an idea on pricing.

I have a neighbor who had asked me once about installing a diesel tach in his dad's one owner truck. He has a spare tach but I don't know if it is a diesel tach. It might be a gasoline one possibly, and he could use that diesel one if so...

Here is some beneficial reading for the OP:

https://www.garysgaragemahal.com/tachometers.html