C4 transmission for 77 f150 why don't they have rpm Gage and can we replace add one In to chk the rpm changing in the truck

Asked by Jul 08, 2013 at 03:44 PM

Question type: Maintenance & Repair

I hope this is not a
dumb question but why
does the truck not have
an rpm Gage ... I just
installe the vacuum
modulator and I want to
test out the gears
changing when I'm
driving... As I mentioned
the problem I had was
the truck was running
high and not changing
gears that I noticed.

3 Answers


Add an inexpensive tach. Did you try manually putting it in 1, 2 then drive? Did it shift? Often, the linkage and steering column collar wear out and it becomes easy to select "2" when the indicator says "D".


In 77 we still had the 55 speed limit so the manufactures deemed that a tach was not a necessary piece of equipment. Usually when a modulator goes bad you will either start burning tranny fluid with resulting white smoke out the tail pipe or shifts become stacked, like high gear at 15mph.

Yes I noticed that to get to D it clicks twice getting there.. Also at one Point I felt like it was on neutral - a tach is a gage ?

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