3.21 gears in a 14 bolt

[russgt]

I recently parted out my grandpa's all original 61k mile 1980 Chevy K20. I was expecting to see 4.10s in the axles as no optional ratio was listed on the spid. Needless to say I was quite surprised to see 3.21s instead. This is the first one I have ever seen, how common were they?

4.10s on left, 3.21 right

[Ziegelsteinfaust]

Not to common as I have to find a set for my truck. I am half hearted looking though. They would likely be more common in delivery vans like the D61 if my research is true.

From what I see 3.73, and 4.11 are the most common in the 14 bolt.

[Liddy71]

I have one in my 86 2wd 3/4 crew cab

[Chevyman350]

Originally Posted by russgt

I recently parted out my grandpa's all original 61k mile 1980 Chevy K20. I was expecting to see 4.10s in the axles as no optional ratio was listed on the spid. Needless to say I was quite surprised to see 3.21s instead. This is the first one I have ever seen, how common were they?

4.10s on left, 3.21 right

Great find, (you looking to sell?)

[blakeduren]

My 83 C20 454 Suburban has them...I was surprised to find them also! The tow ratings for my truck jump quite a bit from 3.21 gears, to 3.73 gears, to 4.10 gears!

[slotard]

I know this is an ancient thread but I sure am jealous, I'd even be happy with a 3.73... my truck certainly doesn't enjoy freeway.

Any suggestions on where to find taller geared 14FF?

[nonstop]

Originally Posted by slotard

I know this is an ancient thread but I sure am jealous, I'd even be happy with a 3.73... my truck certainly doesn't enjoy freeway.

Any suggestions on where to find taller geared 14FF?

I always seemed to find the 3.42s in Suburbans. The trucks were more 3.73s and 4.10s. I am in the midst of trying to convert mine from 4.56s to 3.73s. I having more trouble finding reasonable 3.73s for the Dana 60 than I did the 14 bolt.

[slotard]

If you're in the Bay Area let me know if you find a 14FF with 3.73s in it, especially if it has the G80 locker (I have a C20, not a rock crawler, so I'd prefer a streetable locker even if it isn't quite as strong as something aftermarket). 4.56... wow, with normal tire sizes your truck must scream on the freeway.

[Firebirdjones]

Originally Posted by slotard

I know this is an ancient thread but I sure am jealous, I'd even be happy with a 3.73... my truck certainly doesn't enjoy freeway.

Any suggestions on where to find taller geared 14FF?

Easier to run a taller tire on it if you haven't tried that already.
My 79 1 ton has 3.73's and with it's original tire size of 9.5 x 16.5 they are listed at 30.5" tall. It'll cruise easily at 65-70 mph at about 27-2800 rpm. The 454 runs perfect like this, I've criss crossed the country like this a couple of times going more than 2,000 miles with it and knock down 14 mpg doing it.

A couple of my other cars also have 3.73's with 28" tires and they cruise along at 65mph pretty easily as well. I just don't get in a big hurry. 65-70-ish is all I care to go anyway.

[Firebirdjones]

Originally Posted by blakeduren

My 83 C20 454 Suburban has them...I was surprised to find them also! The tow ratings for my truck jump quite a bit from 3.21 gears, to 3.73 gears, to 4.10 gears!

Yeah I noticed that too, identical trucks and tow ratings increase when they have more gear in them. Makes sense.

[slotard]

Originally Posted by Firebirdjones

Easier to run a taller tire on it if you haven't tried that already.
My 79 1 ton has 3.73's and with it's original tire size of 9.5 x 16.5 they are listed at 30.5" tall. It'll cruise easily at 65-70 mph at about 27-2800 rpm. The 454 runs perfect like this, I've criss crossed the country like this a couple of times going more than 2,000 miles with it and knock down 14 mpg doing it.

A couple of my other cars also have 3.73's with 28" tires and they cruise along at 65mph pretty easily as well. I just don't get in a big hurry. 65-70-ish is all I care to go anyway.

The numbers on my tires work out to 30.5 and with the 350/350 it really feels to me like I'm spinning it fast past 60... but then again, I'm used to newer cars and overdrive transmissions, so maybe I'm just not used to what I have to spin it at. I'm not sure what size I can manage to fit without rubbing on the utility bed I have, I'll have to make some measurements and figure it out (how much travel I have to the bumps, how much compression of the bumps themselves I expect, how much travel I have until the tire hits something.

At this point it'll spin a tire off the line with a utility bed full of tools, I'd rather have it do better on the freeway instead. 3.73 probably makes more sense than any taller than that, it's almost exactly a 10% difference and I'd be surprised if I could fit 34s without rubbing which would do the same to gearing.

[russgt]

Here is the picture again, I do want to mention that with a stock 350 and short 30" tires, the truck was a dog. Notice how thin the 3.21 ring gear is compared to the 4.10.

[Chevyman350]

Those gears are out there.

I found a set on evil bay awhile ago. you just have to keep and eyeout and get lucky.

[85raiderburban]

You'll find these commonly in 2wd 3/4 ton Suburbans and crewcabs. My '80 C20 Sub came with them. I found out when i installed an aftemarket tach and punched in the specs into an RPM calculator. If your motor has decent TORQUE, (400 lb ft +) you'll move these tall gears with 33's no problem all the while having decent lower highway revs. (1800 @ 60 mph)