Hi Ray,
I believe you are seeing what you are seeing, but.... unless you did
something to the truck to change the final ratio, there is no way this can
happen. Now a poorly tuned engine could suck more fuel to maintain the same
RPM & speed as a well tuned engine, but a gear ratio is a gear ratio.
Is it an automatic? Did you do anything to the tranny this weekend?
Now you've got me wondering if maybe your ignition system was affecting your
tach reading -- this used to happen a lot with certain aftermarket tachs.
Poor wires, caps, rotor, etc. would cause noise affecting the reading, but
it was usually drastic, not subtle like you describe.
Anyone have any ideas on this?
Terry.
<raymond.irons@gm.com> wrote in message
news:OF8F1A4916.6BA2F5BF-ON85256C60.00569906@mail.gm.com...
>
>
> <snip> Why would a tune-up change your cruising RPM? I don't get it.
>
>
> Beats me. The only thing I can think of is the combination of cleaning the
> TB and replacing all the other parts, let the engine work less to produce
> the required amount of power to produce the desired speed. I know, the
> final gear ratio is what determines engine speed, but if the engine is
> properly tuned, using good quality parts it will run better. Maybe, thats
> what accounted for the slight drop in cruising RPM.
>
> Ray Irons
> Dover, DE
>
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