RPM and alt pulley..I'm stumped

[Odlaw]

Hey Guys, in all the discussions about getting the wrong size pulley when buying a AdvancedPepZone reman alternator......I checked my reman, and sure nuff it has the small pulley - roughly 2 7/16ths across(diameter) at the lip. Went to local alternator shop, guy was cool just traded mine out and swapped it for me...for free....now I have the larger pulley - roughly 2 5/8ths " diameter.
Here are my findings;
Small pulley - idle = 700 rpm
55 mph = 1600 rpm
60 mph = 1750 rpm
65 mph = 1850 rpm

Larger pulley - idle = 550 rpm
55 mph = 1450 rpm
60 mph = 1600 rpm
65 mph = 1700 rpm

I've got 3.42 gears and my tires are a tad bit taller than stock (stock are 30.5" tall and mine are 31.7" tall with a circumference of 99.7")
Can anyone point me to an online calculator or do you know what rpm I should be turning at these speeds?

Thanks

 

[Odlaw]

OK, not so stumped now - finally found a gear/rpm calculator.
Are the nv4500 tannys .73 or .74 overdrive ratio?

 

[tracy]

I also have 3.43 gears and the large 2 7/16 alt. pulley, and 31.6 dia. tires 265/15 16's but see rpm versus mph similar too your small alt. #'s lol. MY real speed (gps) is 2mph faster than what my speedo shows, 58mph speedo is really 60mph due to the non stock tires.

I have used this calculator a few times and seems good. http://www.angelfire.com/fl/procrastination/rear.html
The 4l80e trans. has a .75 OD ratio, Opps just noticed you have a standard, guess thats why theres a difference in our #'s, hmm can't remember off hand what the 5sp OD ratio is .72 or is it .68.

 

[tracy]

Just read in a couple of places they say nv4500 is .73 OD ratio.

 

[Sunshine]

Try this
http://www.4x4wire.com/tech/applications/gearandtire/

 

[Odlaw]

I also have 3.43 gears and the large 2 7/16 alt. pulley, and 31.6 dia. tires 265/15 16's but see rpm versus mph similar too your small alt. #'s lol. MY real speed (gps) is 2mph faster than what my speedo shows, 58mph speedo is really 60mph due to the non stock tires.

I have used this calculator a few times and seems good. http://www.angelfire.com/fl/procrastination/rear.html
The 4l80e trans. has a .75 OD ratio, Opps just noticed you have a standard, guess thats why theres a difference in our #'s, hmm can't remember off hand what the 5sp OD ratio is .72 or is it .68.

2 7/16 is the SMALL pulley
My new pulley is almost 2 5/8ths and now my rpm's are right on the money - confirmed by the calculators you guys posted here.

Thanks BTW

 

[tracy]

2 7/16 is the SMALL pulley
My new pulley is almost 2 5/8ths and now my rpm's are right on the money - confirmed by the calculators you guys posted here.

Thanks BTW

Thanks for pointing out. I made a mistake, meant to say I have the large 2 5/8 to the outside flange. (or 62mm pulley measured to the inside grooves)