K10 vs K20 - a few questions:

[jocko]

Good evening gents - I've been reviewing a few prior threads on this question and would like to get a little more info if someone could help.

I've read that:
a) 1/2t and 3/4t trucks' frames have a different section modulus (3/4t being greater)
and
b) that 4x4 trucks used the same frame...

So, is it the case that 1/2t and 3/4t 2WD trucks have a different section modulus and that 4x4's used a common 1/2t frame (i.e. 1/2t frame on the 3/4t truck)? Which would be the case? Conflicting info out there.

Also, my understanding is that while the k10 would have a 12 bolt rear end and the k20 would have either an eaton or D60, that BOTH k10 and k20 would have a dana 44 front axle - except that the 3/4t dana 44 is "beefier"... Can someone shed some light on that statement? i.e. define "beefier"?

Also, understand that the rear springs have a few more leafs on the 3/4t vs 1/2t(?)

Any other major differences I'm missing?

I'm kinda sorta lookin at a k10 - but had previously had my mind set that I would wait and find a k20. The more I research, I am not sure there is a whole lot of difference in capability - at least not as much as the difference between a c10 and c20, for example.

So, interested in your thoughts. Also interested how many folks out there run a snow blade on a k10 - and whether it seemed sufficient, etc. I would potentially be running a plow - private use, nothing major, but also wondering ifa k10 is sufficient to that task. I know many have done it in the past, I grew up around k10s plowing. But back then, I didn't know the difference. Guess I still don't!

Thanks for your time.
jocko

[too much stuff]

As far as i know the dana 44 fronts are the same other than the big/small lockout. Not positive however.
As far as the plowing, i have a 7.5' western plow on my 71 k-10 and it handles it no problem. My truck does have the 3 leafs up front. I have seen the 1/2 tons with 2 or 3 leafs.

[jocko]

good info, thank you - any significant difference between the big/small lockouts? (strength-wise, that is - or any other implications)?

A plow part-time would be the biggest stress I'd be putting on the truck, if that, whereas my 71 C20 may see some camper time. I suppose dump the C20 and look for a K20 and use it in double duty for a camper in the summer and a plow in the winter - but where would the fun be in that!?

Normally, I try to minimize the number of trucks I have because I move fairly often (and shipping sucks) but probably looking at re-settling in the midwest someday sooner than later, so there wouldn't be many more moves...

Hmmm.

[jocko]

Hey Sideways - your camper is big enough to have cabover sleeping, but it doesn't hang out the back like some of the 8.5 box stuff. Seems a perfect size that a 1/2 ton truck MIGHT be able to handle. Thoughts?
I might get close to exceeding max gvwr... don't want to do that.

[Stocker]

Not positive but I believe brakes, wheel bearings, & probably axles are stouter on a K20. And since the rear is a FF, if you do manage to snap an axle, the truck won't collapse.

[jocko]

Thanks stocker - good points. I'd be pretty happy as long as I had disks up front (even regular 1/2 ton disk brakes), and a 71/72 is my primary focus for right now. Realize I could always convert a 70 easily, but would like to start with factory disks.


here's a follow-up - rear end gearing...

Lit I have shows:
4.57 as stock (4.10 as an option) for a K20
but
3.73 as stock (3.07 as an option) for a K10

That's quite a big difference. Granted a K20's outside tire dia will be a little larger, but a 4.57 vs 3.73 is a major difference. I can't even imagine selecting a 3.07 as an option for a K10... I'd have assumed 4.10 would have been the option in the 12 bolt.

Interesting. Since it would see some highway time, maybe a k10 really is the way to go. Both come with TH350s, so no real difference there. And changing over to an o/d trans is a major endeavor (because includes moving the engine fwd an inch or two), so perhaps I could live with a TH305+3.73 - but not so much TH350+4.57 (caramba!)

[Stocker]

Not sure about your literature -- and the answers can probably be found here by searching -- but I bet a lot more K20s came with 4.10s than with 4.57s. And 4.10 isn't far from 3.73. But I understand your point, highway gearing is a priority for you. My K20 has 4.10s and 33-12.50s (actually not much taller than my OEM 7.50-16s) and it's not too bad on 55 mph secondary roads. Freeway travel is a bit much, though still doable.

[SS Tim]

Here are the frame numbers again,

C Blazer
C10 115
C10 127 6.04" height 2.53" flange width 0.156" thick 2.98 section modulus

C20 127 6.11" height 2.46" flange width 0.194" thick 3.71 section modulus

C20/30 133 (Longhorns) 7.20" height 2.77" flange width 0.194" thick 5.05 section modulus

C30 157 8.18" height 2.97" flange width 0.224" thick 7.29 section modulus


K Blazer
K10 115 6.02" height 2.71" flange width 0.141" thick 2.70 section modulus

K10 127
K20 127 6.09" height 2.75" flange width 0.186" thick 3.48 section modulus

As far as the gears go, well the footnotes (reading them helps) make all the difference so here is the 72 factory chart to clear things up.

But for a 350/auto K10 3.07:1 and K20 4.10:1 are to be expected.

Finally here is a K10 that spent its whole life with a plow, its on the dealer invoice.

[special-K]

Do you plan to use it as a truck where any of this even matters? To tell the truth,I believe a K/10 and a K/20 bought and used for the same use could have survived the last 40 years virtually equally. I just prefer the 8-lug trucks,especially a full-floating axle. There was a time I thought the K/20s were way more truck. Never even knew they had the same front axle as a K/10. The K/20 is the top of the 4wd model food chain and that has appeal to me. They are the king. But,nothing wrong with a K/10. They are plenty of truck. Most K/20s weren't worked to their limits and K/10s that were pulled through. I am detail oriented,yet don't waste time getting hung-up on details that mean little to nothing when it comes down to it...and it has come down to it for many years

[ryanroo]

at some point in the use of D44F in the GM trucks there was a difference in the K20s and K10s. all of the parts internally are interchangeable but a K20 housing has thicker wall tube. i remember looking at a K20 housing we have lying around and seeing some pretty zesty tubing and comparing it to my 72 K10 i had at the time. i really don't remember what the difference was but it is noticeable. that would lend some durability to the housing, but i doubt it would be a concern. if you are having durability issues with a D44 it will be because of the axles or R&P.

Brakes are another good consideration. the fronts are the same. the rears will be mo betta in a K20, but that is a bit of an issue since the parts are hard to find.

personally i am a K20 nut. but i look at K10s all the time. i usually swap all the drivetrain out for bigger badder more modern stuff anyhow, so as long as it is a K model i dont really care. every chevrolet i have had since i started buying real cars was a 20 or 30 with the exception of my SWB K10 i had years ago

[jocko]

great insight - was really hoping to hear from those that have personally owned and driven both, and I have. Agree on the rear brake comments and, depending on dana or eaton flavor, the difficulty in locating parts (and the cost once you do) after having redone my d60 in my c20. Not cheap!

This has been very helpful, and it brings me down to a decision point:
I can either...
a) keep my c20 and use it as a camper hauler and long-term project AND grab a k10 for a plow truck

or

b) sell the c20 and continue looking for that "special" K20 to use as both a camper hauler in the summer and a plow truck in the winter.

I don't think a k10 would be an ideal platform for hauling a large cabover camper, so that would be the dividing line.

Considering I have no camper yet AND I live in the mojave desert where it snows once every thousand years, I'm not in a rush yet. But this all came up when I found a sweet K20 Cheyenne Custom Camper that really got me wondering whether I should've gotten a K20 rather than my C20 in case I end up back in the midwest. Unfortunately, that dream k20 cheyenne custom camper sold a while ago, so still lookin. This line of questioning came up when I came across a potentially nice k10. Have been in contact and awaiting more details.

I really appreciate the input guys, thank you.

[mrein3]

For what its worth I run a plow on my K10 in the winter. I've never had a problem but I've only used it about 5 or 6 winters.

When I was younger my buds and I had a rule of thumb when buying a 4x4 truck: If it looks like it had a plow - walk away.

Its my opinion that for light duty plow work a K10 is fine. I only plow my own driveway and and maybe a road on the lake if it gets deep out there. If I wanted a plow/camper truck I would for sure go with a K20.

Regarding gear ratios, my axels are 3.73s. A 700r4 would be perfect for my truck and is on my list of wants. A good friend of mine had a '66 K20 with 4.57 gears when he lived in the state of Wyoming. With his single tank behind the seat we had to fill up at the last station before the trailhead, take a jerry can of gas with, and fill up at the trailhead to get back to the gas station when we went elk hunting. He could pull a house off its foundation but couldn't pass a gas station.
I'd stick with 3.73s or 4.10s if given a choice.

[jocko]

Thanks! Yep, the gear ratios are a big deal to me. And based on the research I've done on my C20 and the potential to swap down to a 3.73 from my 4.10, I'd prefer to buy the truck WITH the gears I wanted and then go from there. And 4.57, or even 4.10s are not my first choice. 3.73 just about perfect. And a 700R4 swap would be in the future, just like your plans. Lots of good info on here on what is involved in that - advanced adapters o/p for the trans and the 2" bump fwd on the motor, etc. Thanks for the input - I suspected a k10 might be just fine for plowing, really appreciate everyone chiming in with their experience. All seem to be saying the same thing. Hmm, maybe I DO need 2 trucks after all... Ha.. (C20 for the camper and K10 for the plow). Oh, who am I kidding, I don't "need" 2, I WANT 2! Just wish I didn't need to move em across the country every now and then...

[ryanroo]

I did a little bit of towing with my K10. mostly moving dead cars for my friends(i was the mechanic in my group of buddies in college) i also helped many people move. not a real test of usability, but it was an idea. the K10 was a 350/350 truck, mildly built. it has 3.73s and 33/1250-15s. towing it was Ok. the fact that i was a little better than stock in the power department was a big thing there. it also traveled down the freeway OK. i usually stuck to the 60mph country roads simply to keep it from spinning to hard all the time.

my 72 K2500 was my favorite so far. it was a 350/465 truck that i swapped a NV4500 into. by far the most usable truck of this vintage i have had. i hope my current build will trump that one, but time will tell. anyhow, it would cruise the freeway with traffic all day at 2100 rpm. i swapped the D60 for a 14bolt so that was a non issue. i didnt do any towing with it, but i did a little hauling. it was fine, no better than any other, exception being the fact that it would go further on a tank of fuel and i didnt have to choose not to drive on the interstate. it has 4.10s and after the tranny swap, it was great. had the power to pull and accelerate and still didnt tach out when cruising. it was also much quieter to drive with.

my green 72 K20 i am currently rebuilding was a 4.10 truck before i torched it all apart. i pulled a skid steer and lawn mowers with it on several occasions and hauled whatever i wanted too. outside of a seriously odd engine transplant that had some drawbacks, it was no better or worse than most of the older trucks i have pulled with. it was a 4 speed and other than the engine, totally stock. it was never used as a long trip truck, so i never had any freeway experience, but just driving the country roads i can tell you it was not a speed demon. the rule of thumb with stock tires (235s IIRC) and 4.10s is 55mph is 2500 rpm.

so, IMO if you want a truck that will suit your needs as a hauler/tower/plower in one package, get a K20 and do an OD swap. it will make the truck a much more usable and pleasant vehicle. if you are gonna have 2, i would still look at doing the same thing. 4.10 gears are best in a truck that has to work. it allows for easier starting when loaded which is better for the clutch or auto, has better compresssion braking in a manual and generally makes towing much easier. if you want a freeway driving truck, you have to do what the oems did. switch up to an OD trans and keep the 4.10s. the lower gears will also help if you choose to increase the tire size.

like i said, i am a K20 fan...

hope this helps muddy the waters...

[jocko]

are there any additional considerations in swapping in an o/d trans in a K20 than there are in a K10 that you are aware of? For K10s, I realize the motor has to move fwd a bit and the trans needs an o/p adapter, so I assume it'd be the same deal with a K20(?)

[ryanroo]

all of the Od swaps ive been involved with, we moved the transfer case back. IMO it is the more reasonable approach. it does require that the drivelines be modified/replaced, but from an overall function standpoint, it is better. it wont necessarily be easier and moving the engine isnt terrible either. i just prefer to move the t-case. in these trucks its pretty easy to do the engine forward. all the 2wd stuff works as far as the shroud and rad hoses i think

i am not familiar with the term o/p. i am guessing it is output? i think the 700r4s need a different output. the only time ive done anything with 700r4s in these trucks was to replace one with a NV4500.

the K10 and K20 frame and locations are all the same. so, whatever the requirements of a K10 will be the same for a K20. also, there is the capacity consideration. if you are using the truck as a heavier truck, i would really consider using the modern 3/4 ton transmission. that would mean a 4l80 in a K20 as opposed to the 700r4. the 700r4s can be built well, but depending on the year that they are sourced from sometimes the upgrades can add to the cost a bit and in the end, it is still a lower rated transmision. i prefer to spend the money once and go a little beefier myself. that will really depend on the amount of weight you plan to put in it, or how hard you are going to push snow. plenty of 700r4s are out there and doing fine. the transmission choice will also dictate what additional stuff you need. if it is a auto to manual swap there will be output/input differences in the transfer case and transmission. if you go to a 4l80 the input wont match anything stock. niether will a NV4500. they both require an adapter spud shaft, or a newer 32 spline input 205.

i hope i dont sound like i am trying to dissuade you from your plan, these are just my opinions and choices. ive done a few swaps in these trucks and many others and there isnt a set in stone right or wrong. except my way, its always right !

[jocko]

ha, no not at all ryan - I appreciate the input. Yes, o/p was output, I was specifically referring to the Advanced Adapters TH350 output shaft/housing adapter that I've seen most use when they move everything else except the t-case. An approach I hadn't considered, btw - just assumed it'd be harder since most seem to go for moving the engne fwd - so this is great info. I'm more used to just chopping the driveshaft on most trans swaps I've done anyway, so what you're saying makes sense if it's not too hard to relocate the t-case.

[special-K]

Adding an O/D transmission is exactly the same between K/10 and K/20. We've discovered that moving the engine forward to leave the transfer case/driveshafts alone is the best way to go. The K-model engines sit plenty far back to allow for moving forward with no radiator clearance issues.

[jocko]

thanks Tim, my impression also (that the eng fwd was perhaps the best approach), but wasn't sure if same between 1/2 and 3/4, all cleared up now - appreciate the input everyone.

[ryanroo]

i am curious why it is considered "the best" i personally think it is the lesser of the two options for a few reasons. i think there is a difference between easiest and best.

I'm not trying to bicker, i just keep seeing people choose and promote this method and i am curious why it is so

ryan

[jocko]

ryan - perhaps a poor choice of words in ME saying best, since I haven't done either approach yet - so maybe I should re-word it to say the best approach FOR ME, because I have a better understanding of what is involved in that approach vs the t-case move, that's all. I'm trying to determine which approach is best, and I guess since more folks seemed to have done/attempted/had success moving the motor fwd, I'd lean toward that approach for now - but will have to look at the problem more closely if/when I buy the truck to know what is involved in each approach. Not writing off the t-case shift backward, but I am leaning toward the other way that most folks seem to have approached the problem - and I haven't necessarily seen a "technical" case yet presented that makes either best, per se, nor easier, other than simply personal preference. I'd like to see the techncial case for why either approach is better / easier also.

[SS Tim]

Might try this thread for some more info. :-)
http://67-72chevytrucks.com/vboard/s...d.php?t=495513

[SS Tim]

For Jocko's needs I think moving the engine is the best choice and least invasive. It is one he (or anyone) can do in his garage (or carport) without having to modify driveshafts, the trans. shifter or hack a new hole in the floor. The less you disturb the more liklely a positive outcome. Now on a clean build like a frame off or a full driveline swap moving or even changing the transfer case both have merrit. In fact there is alot to be said about simply using a 700R4 and a 208 case.
But again for Jocko, sliding the engine forward will help him have an easy and successful conversion. Plus it is also completely reversable to a stock configuration. Not to mention the weight savings of 4" of cooler line!

[ryanroo]

I think i sounded a little harsh without intending to. i do see the merits of the engine forward method, especially in situations where your tools make it the most feasible. and that would make it the best choice in that case.

as they say, when you are a hammer, everything looks like a nail. i am a fabricator in my daily life, so none of the required mods to move the t-case back look very difficult to me. the benefits of that method also seem better to me, so i like it more.

from a technical point, moving the engine forward has some performance drawbacks. in any form of motorsport, you will never find someone trying to shift the weight forward in a front engine vehicle(except maybe truck pulling). the more evenly you can distribute the weight between front and rear the better. trucks are already poorly balanced. also the further you can get the front output of the transfer case from the front pinion the better. less driveline angle leads to better joint life and less likelihood of vibrations. obviously this has limits too. your rear shaft needs to have a decent angle and length.

the reason i would guess most people choose the engine forward method is because it poses the least modifications. thats not a bad thing, but having worked in the performance 4x4 world for a while, and doing what i do for a living, i see things differently i suppose.

[Vintage Windmills]

Ryan, I am glad you are debating this since I am too with my K20. I like the idea of putting the engine in the same position as a 2wd to mitigate distributor service. I think the concern over the weight distribution being further forward is probably not significant. You are only talking about what, a 20lb additional load on the front axle? The K10/k20 would still be better balanced than a C/10 C/20 since the engine is no further forward than in those trucks and you have the beefy np205 far back. On the other hand, I do like the idea of a stock appearance with the deep fan shroud.

Tim, the section modulus you posted for the K10/K20's seems low relative to the C20 based on the dimensions posted. My mechanics of materials book isn't handy and I'm feeling lazy so i haven't checked the math yet.