Downshifting from Overdrive over 55 mph

[CrashDriver]

Hi, I was reading through the owner's manual that somehow was still with my 88 ranger when I bought it - in the shifting section it warns you not to downshift from overdrive over 55 mph.
I'm curious if there is a legitimate reason for this, or if it's just kind of a generic safety warning?
If I were trying to overtake someone on the highway going say 60 or so, I would logically want to downshift into fourth for more power and it wouldn't really be a big jump at all; so I wonder why the warning.

 

[RonD]

That would be generic recommendation just at the end of 55mph speed limit, lol

Best power(torque) for non-3.0l engines, lol, was about 2,500rpms

If you were running 3.73 axle with 26" tires at 2,500rpms in 4th(1:1 ratio)that would be 52mph
In OD(.85) that would be 61mph
I would downshift

But best MPG is with RPMs at about 2,100, close enough to best power to maintain speed but not lugging the engine too much

 

[SenorNoob]

RPM would be my guess. You can always calculate your actual RPM at a given speed. Here is a really good tool for that.

Gotta keep in mind that 55 was the national speed limit at the time. There was really nowhere to go any faster so the trucks were designed for that.

Edit: Ninja'd

 

[CrashDriver]

RPM would be my guess. You can always calculate your actual RPM at a given speed. Here is a really good tool for that.

Gotta keep in mind that 55 was the national speed limit at the time. There was really nowhere to go any faster so the trucks were designed for that.

Edit: Ninja'd

Actually my truck is one of the ones that actually comes with a tac so figuring that out isn't a big deal; but that's good to know

 

[CrashDriver]

That would be generic recommendation just at the end of 55mph speed limit, lol

Best power(torque) for non-3.0l engines, lol, was about 2,500rpms

If you were running 3.73 axle with 26" tires at 2,500rpms in 4th(1:1 ratio)that would be 52mph
In OD(.85) that would be 61mph
I would downshift

But best MPG is with RPMs at about 2,100, close enough to best power to maintain speed but not lugging the engine too much

that's good to know, I was hoping that was the case. Thanks for all the info