The Stovebolt Site Forums The Shop Area Driveline gear nomenclature.

In my line of work, which is in the auto/ commercial truck repair/mechanic.We talk of a vehicle being low geared, as in 4:10 and higher.A high geared vechicle will be 3:73,3:55,3:07 and down. Here is how i will explain by way off my 54 3100.when i got the truck back in 78, it had 4:10 gears.4 spd manual. At 55 mph the rpm was pushing 3000. A few years down the road i had some issuse and i put a diff in with 3:90. Same trans, same 55 mph, lower rpm,as such i could go a little faster when i started pushing the 3000 rpm. Many years later a diff with 3:07 ratio went in with a 4 spd Saginaw.At 55 mph,rpm was down in the lower 2000 rpm range. Step on the gas and by the time I'm back to pushing the 3000 rpm mark, im also doing 70 mph. My numbers are ball park but close. Im not too fussy on being exact. Higher the gear ratio number the slower one goes. Lower ratio numbe, the faster one goes. Trucks/ pickups built for work need to be low geared 410 and up,off road vehicles get up into the 5's thats stump pulling gears,highway cruising cars will get into the 2's. Even in hiway trucks that run the hiway,pulling a walmart trailer will will have a gear ratio in the 3's, log trucks , heavy equipment haulers will be in the 4-5 ratios,
So when i hear someone ask, my engine screams at 55 mph what higher ratio can i go to? If he tells me hes not happy with 3.73 ill tell him to go 3.55 or 3.07, or 2.56.....at that point when he gets up to 55-60 after a mile or two his engine wont be screaming be cause it only turning over at 1800 to 2150 rpm, again only pall park.