I think we can all agree the NP435 was standard in SOMETHING... right?? LOL.
Right. And stock in Ford trucks to boot!
I plan to change to a lower number (higher gear).
You might verify two things.
First, which gear ratio is in the rear end right now. For V8 equipped Broncos that was either 3.50 or the optional 4.11, but could be anything after all these years.
I don't know anyone who has ever gone below 3.50 in a Bronco.
And second, find out why you're tapped out on the freeway.
Are you running out of rpm, or are you running out of power. Could the cam be going flat? Could the carburetor be under-sized, or having other issues? Could the choke plate be partially closed even when fully opened up, thereby limiting the ability of the engine to pull harder when you open up the throttle?
Could it just need a full tune-up even?
Lots of things to consider.
If it's already got a lower gear, such as having been changed to a 5.13 to suit 37" tires that the previous owner had installed and removed, then you may just be well beyond the engine's happy place on the highway.
Without a tach it's extremely hard even for the experienced driver to determine what rpm the engine is running. Especially if the exhaust has been altered.
But figuring out the engine speed vs vehicle speed is a simple matter of measuring a tire exactly and finding out what gear ratio is in the differential. This will avoid the need for a tachometer right away at least.
Don't worry, I do understand Bronco does NOT = Racecar Haha. But I figure its a similar concept for gearing.
Hah! Yep, I'm sure you had a few of us worrying for a minute there.
Definitely the same concepts in putting the rpm where you want/need it.
Good luck.
Paul