coil vs leaf,

[doowopper]

greetings.

i have a 1969 c20 that i bought new. i got it with coil springs on the rear, full well knowing that i shoulda gotten the leafs. the gears are 4:10 as i recall. i am think of putting a better ratio in as well as some sort of posi for pulling a small camping trailer in the desert.. according to a local shop there are no gears available for this rearend. i have the back half of my son's '74 c20. it has leaf springs and appears to have 3:73s. his frame web is 8" and mine is 6" so i didn't spend much time thinking about grafting it onto mine. one option is putting his rear axle under my truck. i will be putting an '03 5.3 ls with its factory trans in it. so here are my questions. is the change to leaf springs worth the trouble or can i add something to the coils to beef up the suspension a little? will the 4:10s work ok with the od trans? the truck will be my daily driver.
thanks in advance for any and all input.

roger

[firedemon]

what rear end does it have in it ? i have a hard time believing there are no gears available . but you could go with helper springs , coil over , or airbags possible other options im sure people will chime in to keep the factory rear

[gmc684x4]

Funny i have had my 68 setup first as coil with hd coil package i could out carry what i can since i swapped to a 4x4 drive train under it

Does your truck have an eaton diff ?
Most common gears are availiable to it most c20 and c30 i seen have a dana 60 under them which have even more gear options

Look for 3/4 hd springs and add bags if you want to carry more weight

You will like the 5.3 ls
I will recommend upgrade to a 4l80e transmission as its 3/4 1 ton rated

[kwmech]

If they are telling him there are no gears available then I would assume he has an Eaton rear. I converted a 69 truck years ago to leaf. I'm not a rear coil fan when it comes to hauling loads in a truck. It was nothing more than finding the frame hangers at the wrecking yard and bolting them on with the correct measurements. By all means grab the 14 bolt and use it. 3.73 seems to be a sweet ratio in the truck even with an OD trans running a stock height tire

[Mike C]

If I was running an OD and my HO52 was in good shape I would keep the 4.10. But that is the lowest numerical ratio that is available and less common than the 4.57 it seems. If the rear is junk then go with a 14 bolt for sure. If you stay on coils, add some airbags and call it good.

[doowopper]

Originally Posted by firedemon

what rear end does it have in it ? i have a hard time believing there are no gears available . but you could go with helper springs , coil over , or airbags possible other options im sure people will chime in to keep the factory rear

i only know what the guy at the shop told me. he ask me to describe the cover and count the bolts.

[doowopper]

Originally Posted by Mike C

If I was running an OD and my HO52 was in good shape I would keep the 4.10. But that is the lowest numerical ratio that is available and less common than the 4.57 it seems. If the rear is junk then go with a 14 bolt for sure. If you stay on coils, add some airbags and call it good.

i've got the 16" rims off the '74 so i can always get a little taller tire i s'pose.

[special-K]

Yeah, you would have the HO52 Corporate rear. If all is good other than wanting to be better set up for towing, I'd put new coils in. Make sure you get 3/4t coils and HD if possible. Some places might just offer one spring for 10 & 20. Then as Mike suggested, air bags that fit inside the coils. They are actually auxiliary air springs. I use Air Lift, but Firestone and maybe others make them. They offer up to 1500# more capacity.

[BigBird05]

I wanted to do just that on my truck. Remove the coil spring rear suspension and add a leaf spring one. I couldn't find a 73 to 84 donor truck within my budget. It should be easy for you since you already have the back half frame with every thing you will need. The only issue I can think of is the pinion length of the donor rear axle. You might have to have the drive shaft length changed.

[diesel burner]

i personally prefer coil sprung rearends, they ride much better than leaf springs and get around better off road. Another option for increasing payload capabilities is the factory installed helper springs that were optional equipment.I think LMC truck is selling them, if not I'm sure you could find a set listed in parts.

[gmc684x4]

If your determend to make it ride on springs why don't you buy a set of 67 72 rear spring hangers of the board be eager then grafting to frames together
There is a chance chevy already put some holes there for leaf hangers

I looked at my c30 already has the front holes to switch to a 4x4 diff

[weim55]

Roger,

If the factory ratio in your axle is 4.10 and everything back there is in good condition I would just leave it alone and run it. The 4L60E transmission factory behind the 5.3 will have a .70 overdrive ratio. Doing the math that calculates to 2.88 in overdrive. The weight of the truck combined with the camper that little 5.3 Will likely only pull in overdrive on flats on the highway. I wouldn’t do anything numerically lower than a 4.10 with your set up, anything lower numerically and overdrive will be useless.

The 14 bolt swap isn’t that difficult if you don’t mind doing a little of fab work. It wouldn’t be that difficult to find and original leaf spring Dana 60 or an Eaton with 4.10 67-72 and I bet money it’s a direct Bolt in to your ‘69.

Steve weim55 Colorado

[doowopper]

thanks for the replies and suggestions. they're all appreciated.

roger

[j_cst_10]

I second weim55 - 4.10 is a good ratio for an overdriven 5.3L. I had a 02 silverado with a 5.3 and did some hauling with it (I think my truck had 3.73's or possibly numerically lower).

That engine was a good engine, but due to the displacement was not a torque monster and did struggle with decent weight behind it (car hauler and a newer mustang from Chicago to Cleveland).

4.10's would be optimum for that set up