C-20 bounces bad!

[Barnfind46]

Here is a little background on my truck. It is a '68 C-20 with 327 v-8,400 trans and corporate rear end with coils. It came with the optional overload springs. The truck was bought new in Delta Junction Alaska by a large company. It was used by them until '97 when it was brought down to the states and registered by the second owner. It had some crazy gears in the rear end like 4.56's. when I bought it the truck would shift through the gears and be in third before it was doing 20 mph.I changed out the rear end to a 2002 14 bolt with 3.73's and 30" tires. now it has much better manners on the highway.Sorry this is getting long winded.I just know the rear end gears were not stock with the automatic transmission. Now to my problem. When I hit bumps or potholes the back of the truck bounces up very hard. It jars my back sometimes. Could the company that bought it new possibly changed the rear springs out to handle some additional weight? I was just wondering if the other members had trucks that rode as harsh as mine. I drove a '68 C-10 back in high school and it rode like a dream. Before I start spending money on replacement springs I wanted some expert advice. Thanks in advance!

[hugger6933]

If you were to say jump up and down on the bumper and hop off does it still bounce? Or when driving and hit a hole does it bounce more than two times? I'm trying to say you may need to check the shocks.See if they leak or just plain wore out

[Barnfind46]

Shocks should be good but I am going to change them. The bounce is more of a very firm rebound. After the bounce the truck is done.

[Arnulfo]

I have a 1970 c20 and it bounces like you describe. I attribute that to it being the original 3/4 ton suspension. C 10 are 1/2 ton which is why they ride smoother.

[truckster]

I've owned both 1/2 and 3/4 ton trucks of this vintage, and the 3/4 ton trucks definitely have a rougher ride. Unless you need to tow or haul heavy loads, the 1/2 ton is a much better ride.

[Shaky]

I took the helper springs off mine. The truck would hit a bump, compress the relatively soft coil springs (if you can call even old C20 springs "soft") and then hit the helper springs, which instantaneously quadrupled the spring rate.

[special-K]

Sounds like no recoil as compared to too much bounce. Could be too stiff shocks. Are the coils aged and compressed to where it is hitting the helpers without the weight on bumps? I've had leaf spring C/20s and I wouldn't say they rode rough empty bad as you describe. I would think coils would ride better.

[custom10nut]

Do you have the Trailing Arm rear suspension? I’m assuming yes.
I had the same issue with my 79 C-10.
It had what my son liked to call “that old truck bounce”, whenever we went over a sizable bump, or through a dip in the road.
While I had everything apart with the brakes and suspension, I went ahead and bought Coil Over Shocks for the front and rear.
Problem solved. The ride is smooth, and the suspension is firm but not harsh.
What you describe sounds kinda like my 1-Ton Dually. Rides nice till I go over a seam in the road or bog pot hole. Then it feels like no suspension.
But then again that’s when it’s loaded it’s fine.

[Barnfind46]

After some research I think the 3/4 ton trucks came with standard or heavy duty springs. I will change out the springs to standard and new shocks. Hopefully that will help. I am trying to get each part of the truck dialed in. It had a lot of issues when I started. Bad brakes,poor steering,worn suspension and engine issues, wiring issues. I have been working on each part one at a time and am getting down to the last few things.At the point that I start the cosmetic part I want the truck where I can drive it comfortably across the USA with no issues. I just like to ask people who have been down the road before I make a purchase.We are a one income family but because I am frugal I am able to keep my truck and enjoy. Thank you for all the help!

[Rick Bollinger]

I would really look into the shocks. Sounds like they may have put some heavy duty ones on at some time. If you are going to change them any way take them off and go for a ride around the block. It will be bouncy but you will get a feel for your springs. I put KYB gas adjusts on my 68 1/2 ton and love them.

[ElKotze]

When I rebuild the suspension in my '69 3/4 ton, I went with HD shocks and HOLY COW! it felt like no suspension at all, changed over to standard and it drives very nice now. Big difference.

[71threequarterton]

Word is, my C20 spent most of its life hauling a camper around for family trips. I don't know if these springs came from the factory or if they were fitted by the PO but this is how I bought it.

Seriously, it's a rough ride - sometimes I even duck when I see a bump coming up so I don't get launched into the ceiling

[Barnfind46]

Thanks for all the reply's! When I get my new shocks on I will report back on hoe it rides.

[Barnfind46]

Sorry for the long time from the last post but wife had some major health issues and I couldn't work on the truck. I finally got the new shocks on the truck and it made all the difference in the world. Now it rides like it should. I am pleased.

[Stocker]

Sorry to hear of your wife's problems and I hope she is doing better.

Thanks for the follow-up, glad that the new shocks helped. If you don't mind my asking, what shocks did you get?

[Coley]

Originally Posted by 71threequarterton

Word is, my C20 spent most of its life hauling a camper around for family trips. I don't know if these springs came from the factory or if they were fitted by the PO but this is how I bought it.

Seriously, it's a rough ride - sometimes I even duck when I see a bump coming up so I don't get launched into the ceiling

Those are aftermarket helper springs.
I put a set on a 1/2 ton I had a few years ago to help with hauling a small 8ft camper.
My truck ('72 Chevy Cheyenne Super) had come with the leaf spring option (vs. the stock coil spring system)...so it was easy to add the leaf type helpers.
When I wasn't hauling the camper (off season), I removed the U-Bolts located on either end of the spring...but left it in there for the time being.
This gave me my stock 1/2 ton ride back....for the time being, which was nice around town.
Come camper season, i put the U-bolts back on and 'dialed 'em down' to get my spring rate up again.

All good
Coley

[Stocker]

Originally Posted by Coley

Those are aftermarket helper springs.
I put a set on a 1/2 ton I had a few years ago to help with hauling a small 8ft camper.
My truck ('72 Chevy Cheyenne Super) had come with the leaf spring option (vs. the stock coil spring system)...so it was easy to add the leaf type helpers.
When I wasn't hauling the camper (off season), I removed the U-Bolts located on either end of the spring...but left it in there for the time being.
This gave me my stock 1/2 ton ride back....for the time being, which was nice around town.
Come camper season, i put the U-bolts back on and 'dialed 'em down' to get my spring rate up again.

All good
Coley

Yup -- they look just like the Hellwig springs I added to my K20. You can change the spring rate by changing the preload on those end u-bolts. The tighter you crank 'em down, the higher the spring rate gets.

[factorystock]

Originally Posted by Barnfind46

After some research I think the 3/4 ton trucks came with standard or heavy duty springs.

Correct. Standard C 20 rear coils 2000 lbs = good ride empty. Heavy duty C 20 rear coils 3000lbs = bumpy ride empty

[Barnfind46]

Took the truck out today and drove on some rough roads and it did great! I have been trying to sort out all the problems on this truck for the last several years and it is now a pleasure to drive. Couldn't have done it without the helpful advice from the great members here on the forum! My wife is doing much better. She had a heart attack on new years eve and quadruple bypass in February followed by a stroke. She is my whole life and always comes first! The truck is my stress relief. She has been telling me to go have some fun with the truck.She is the best! Not to worry though. The Doctors have told us that she has a good chance of a good recovery.

[71threequarterton]

Wow - thanks for the tips on the helper springs, guys but most of all, to Barnfind46, glad things are looking up - that your wife is OK and you're getting to spend time on the truck.

[Stocker]

Major health issues indeed! That's some scary stuff she's been going through. Must feel good to get encouraging words from the doctors. It's amazing what can be done these days.

What shocks did you end up putting on your truck?

[Barnfind46]

I used the Gabriel Ultra Truck Shocks they sell at Summit. Part # G63306. Cost $25.00 each. I hauled an engine across town and the ride was the same. I will see how it does with a full load at some point but so far so good.

[custom10nut]

My ‘70 C-10 used to do the same thing in the rear, as well as “pitch and dive” in the front. The way I died mine was to put “coil over” shocks on all four corners. It rides like a brand new truck now.