would 73-87 rear 3/4t or 1t leaves ride horribly in my 70k20?

[rickcdewitt]

hey guys i'm trying to decide how to beef up the carrying capacity on my 70 k20 project truck and am leaning toward some 73-87 3/4 or 1 ton leaves and moving the rear hanger back 4 inches.

i'm assuming my truck is lighter and don't want it to bounce all over but i like the idea of 1 ton springs for towing a car hauler.i don't care to much about a smooth ride but i do want it to keep traction in 2wd going uphill on a steep dirt road since there are a lot of them around here.

can anyone with one of these later trucks comment on the ride or somebody that knows frames advise on if the 1 ton springs might hold a dangerous amount of weight?

i do want 56" springs of some kind but i'm unsure of which ones would be approriate. thanks,rick

[obijuan]

They ride bad in a 73-87 lol. Get airbags on there. Inflate when you need em to tow and don't have the ride when unloaded.

[rickcdewitt]

are they bad enough to make the trucks loose traction? i can get some for free if i go that route.

whats the ball park for a complete bag setup?

[1976gmc20]

I bought a 1973 k-20 brand new and I never thought it rode all that bad, but then I was a bit younger back then

It was pretty helpless without a load in 2wd with 750x16 bias ply tires

[rickcdewitt]

thanks guys! i think i'll get a good clean set and play with removing leaves from the pack if necessary.should be able to come up with something that holds more weight than stock but rides a little nicer since they're longer.

i'll just have to be sure i get a pack with a similar or higher arch so ride height doesn't go in the wrong direction.

[special-K]

It should ride the same as with your original springs, if not better being longer. Auxiliary bags are the hot lick. Go to www.suspensionconnection.com for more info. I think they offer Air-Lift and Firestone. Both are good quality, but I'm an Air-Lift guy myself. This is what they do and been doing it forever

[rickcdewitt]

Thanks sk. So I guess guys just use the 73-87 bag kits?

I do remember something about bags being short and limiting down travel?

With the 700$ price tag I might look into piecing something together or finding a kit in a junk yard if I go that route.maybe just wait until the trucks together and save it for a later project.

[1976gmc20]

Why don't you just get a weight distributing hitch for your car hauler ????????

[rickcdewitt]

I should have provided more info from the start guys sorry.when I swapped out the c20 frame on my truck I put a k10 frame under it with the understanding I could just swap out springs to make it a k20.right now l guess you'd call it a 5/8t with the 8lug axles.

I don't want to buy new 70 3/4t rear springs since there's much better setups out there for free to cheap. So you see I need to get springs no matter what,I just want to make a smart choice in doing so.

I'm putting new decking on my trailer now and rebuilding the brakes.yes I thought about a distribution hitch,its on the table as far as options while upgrading.

Anyways your input is appreciated,rick

[1976gmc20]

Originally Posted by rickcdewitt

I should have provided more info from the start guys sorry.when I swapped out the c20 frame on my truck I put a k10 frame under it with the understanding I could just swap out springs to make it a k20.right now l guess you'd call it a 5/8t with the 8lug axles.

I don't want to buy new 70 3/4t rear springs since there's much better setups out there for free to cheap. So you see I need to get springs no matter what,I just want to make a smart choice in doing so.

I'm putting new decking on my trailer now and rebuilding the brakes.yes I thought about a distribution hitch,its on the table as far as options while upgrading.

Anyways your input is appreciated,rick

Okay - as far as I know, the LWB K10 and K20 frames are the same - only difference is the springs and axles and maybe the brake master cylinder and plumbing (???).

I have no clue what you're doing... did you start with a C20 and convert it to 4x4 ???

The 1973+ K20 pickups were brutes. They all seemed to have the same rear springs, and GVW was only based on the factory tire size: 7500 for 8ply and 8500 for 10ply. I loaded ridiculous loads on mine: firewood, gravel, and I towed a heavy travel trailer (on the step bumper ball!) and hauled a heavy load (4K# ?) in the bed all the way from Colorado to Alaska, via the then under construction Cassiar Highway (37). The pickup did fine except I blew a couple tires along the way.

Later pickups seemed to have various springs - at least my 76 C20 is fairly lightweight in the back, and of course then they started making 3/4 tons with only semi floating 8 lug axles

The Reese, EZ-Lift, etc hitches are really the thing for hauling a heavy "bumper pull" trailer assuming it has an A-frame tongue. I don't know what they cost these days, but it has to be cheaper and simpler than some sort of air lift overloads.

[mike16]

grease between the leaves makes for a softer ride, that combined with some softer riding shocks.

[rickcdewitt]

Originally Posted by 1976gmc20

I have no clue what you're doing... did you start with a C20 and convert it to 4x4?

c10 to c20 to k10 to k20.350 to 6.0l,t350 to sm465 to nv4500,12blt to d60 to 14bff. Easy right?.its as much of a Johnny Cash caddy as I've ever seen!

As ridiculous as the build has been as goals have changed the question for this thread is easy.

How much 73-87 spring will make a 70 k20 bounce so bad on wash boards it won't go up a hill?

[ryanroo]

I don't think the truck will behave much different than the oem k20 springs would. Trucks are naturally light in the rear and all heavier gvw trucks from that era are bouncy. The honest best of both worlds is the k10 spring and the helper bag. If you can get 3/4 ton 52s free, put them on. If you want to swap the hanger and run 56s that will help, but I doubt you feel the difference with a 3/4 or 1 ton spring.

A complete air bag kit... Mine was quite expensive.... Haha

[1976gmc20]

Originally Posted by rickcdewitt

c10 to c20 to k10 to k20.350 to 6.0l,t350 to sm465 to nv4500,12blt to d60 to 14bff. Easy right?.its as much of a Johnny Cash caddy as I've ever seen!

As ridiculous as the build has been as goals have changed the question for this thread is easy.

How much 73-87 spring will make a 70 k20 bounce so bad on wash boards it won't go up a hill?

How did you convert a C10 to a C20 ??? Just about everything is different except the sheet metal, engine, and transmission.

If you're bouncing on washboards then you need to drive slower. The trouble I had with my old K20 in 2wd was ice or greasy snow. Actually it wasn't that much better in 4wd on ice - the tires were too hard and the springs and frame were too stiff. However, you should have seen it hauling a couple tons of firewood out on a muddy cat trail, and pulling a Land Rover and trailer out at the same time

[rickcdewitt]

thanks roo, i just don't want to cross the line and have little suspension reaction to terrain. i would have went the direction of your build if i hadn't been offered a 6.0l truck for 500$. i might still with another truck later.

as far as c10 to c20.. just slide a c20 chassis under,kind of like the k swap but easier. the washboards are what worry me,you can't drive 5mph if you've got 20 miles to go each way....being from montana i'll give you the benefit of the doubt you know what a logging road is like 76.i've put in my time on units with an 066.

i'm leaning toward 3/4t 56" packs and tuning to work.bags are cool but will the pump and check valves work in 10 years or even 5?

[1976gmc20]

Originally Posted by rickcdewitt

...
as far as c10 to c20.. just slide a c20 chassis under
...

Oh, you replaced the cab on a C20

[rickcdewitt]

I started with a c10 and a rotten c20 shell.I don't like go fast or not being able to fill up the bed so the choice was easy.I don't like getting stuck either hence the rest of this build

['63GENIII]

If you are going to move the rear hanger in order to run 56s, why not move both hangers and run a set of 3/4 or 1 ton 63" springs. They do ride better although Im kind of partial to the set up. They carry as well as the shorter springs and also have the added bonus of riding real nice when unloaded. They also seem to follow the road / trail a little better - they keep the tires in contact a little better. As far as the frame, my 63 has had a pallet of 80lb concrete sacks in the bed while towing a tandem dump trailer with a small backhoe / loader in it. Pretty ridiculous load there but it held up just fine.

[rickcdewitt]

i do like the 63's, i've put some in a toyota and the suspension travel is great.but its quite a bit more work making new front hangers and modifying the crossmember imbetween the hangers to bolt in forward where the frame is taller.since the hangers are outboard of the frame they will tend to twist the frame without properly placed crossmembers to support them.something i won't ignore on a 3/4t.


maybe i'm just getting antsy but i only need to finish my fuel system and wiring to fire up the truck.i've found myself putting off a few things that i want to do later.