3.21 gears in 14bff?

[benchseat4speed]

I was looking at some factory chevy pickup brochures ('74 and '76) and there is a spec list on the back cover for engines/transmissions/ratios etc. According to these spec sheets a 3.21 ratio was available for the full floating axle (14 bolt) but ONLY in the regular cab C20. Has anyone ever seen a 14 bolt with 3.21 gears? Thanks, Kevin

 

[tarussell]

Yep !

Tom

 

[dyeager535]

Yeah, as a matter of fact I think I've got a set of 3.23 gear's from the front of a truck that was so equipped...

3.23/3.21, ring/pinion count isclose enough that either of those numbers is interchangeable.

 

[IDGMC]

Ok. you got me nervous now. I got a set of 3/4 ton axles. When I spun the tire and counted rotaion/driveline rotation...it didn't seem right. So then we pulled the covers and counted teeth. The front figured to be 4.10...and the rear well with a gov-lock in it it was hard to see the pionion but i think 4.11. Why if I spun the tire would I end up with a higher gear ratio? FREE WHEELING?

 

[benchseat4speed]

Remember when checking gear ratio on an open diff to only raise ONE tire off the ground. Count the rotations of the driveshaft and multiply the # of driveshaft rotations by 2 to get the ratio. For a 4.10 open, the driveshaft should rotate 2.05 times for every one turn of the wheel that you have off the ground. You don't do this with lockers or posis, for those raise BOTH tires and spin em once, the pinion will give actual ratio without multiplying by 2. For 4.10's, the driveshaft will spin exactly 4.10 revolutions to every one of the tire. Kevin

 

[79k20350]

Remember when checking gear ratio on an open diff to only raise ONE tire off the ground. Count the rotations of the driveshaft and multiply the # of driveshaft rotations by 2 to get the ratio. For a 4.10 open, the driveshaft should rotate 2.05 times for every one turn of the wheel that you have off the ground. You don't do this with lockers or posis, for those raise BOTH tires and spin em once, the pinion will give actual ratio without multiplying by 2. For 4.10's, the driveshaft will spin exactly 4.10 revolutions to every one of the tire. Kevin

x2, or if you cant do math rotate the tire 2 times

 

[benchseat4speed]

x2, or if you cant do math rotate the tire 2 times

Or you could do that!!

 

[beater_k20]

Ok. you got me nervous now. I got a set of 3/4 ton axles. When I spun the tire and counted rotaion/driveline rotation...it didn't seem right. So then we pulled the covers and counted teeth. The front figured to be 4.10...and the rear well with a gov-lock in it it was hard to see the pionion but i think 4.11. Why if I spun the tire would I end up with a higher gear ratio? FREE WHEELING?

no need to be worried, with 4.10/4.11 you're safe. hell, if you had 4.09/4.11 you'd be good.

 

[u2slow]

I picked up a 3.21 14bFF for my Burb to get some highway legs. I believe it was from a mid-70s C20 with a BBC.

I got a 3.23 10b front from an '80 K20. It would have had the 3.21 14bFF for the rear.

My Dad also has the 3.21 in a '79 C20 crew (BBC as well.)