The Stovebolt Site Forums The Shop Area The HiPo Shop Extremely bouncy after refurbing springs

My '40 has stock springs and a GM 10 bolt rear. It uses tube shocks, mounted at the bottom to the spring mount, and the tops are mounted to a square tube crossmember added just behind the rear axle.

Before I began, it was a pretty harsh ride, meaning the rear suspension was stiff and the truck took bumps and potholes really hard.

So I removed the rear springs, sanded them, put a coat of Rustoleum Rusty Metal Primer and then coat of Rustoleum semi gloss black. When I put them back together I used those teflon strips, I think I got them from Speedway. I grounded down the edges a little on each leaf to make them more rounded thinking they would slide better against each other. And also I installed new rear Gabriel shocks. I used all new hardware. The round-headed bolt that holds the spring pack together broke, so I replaced them with a rgular stainless bolt that I just rounded the head on with a bench grinder. Everything is super tight, I didn't use a torque wrench, just tightened everthing by feel.

Anyway, I took the truck out for a run last night, and it's kinda strange. On a perfectly smooth flat stretch of road, it bounce up and down constantly. It feels like a carnival ride. On the plus side, it takes bumps and potholes and rough roads a lot smoother than it did before I started, but I can't figure out this weird bounciness on flat smooth roads. It's like riding a bike if the front wheel was an oval shape instead of round.

I didn't touch the front, just the rear.

Any ideas?

Incorrect or defective shocks?

I suspect as Beltfed mentioned, the shocks are to loose.

Joe

Shocks are too loose? Explain...

It's very rythmic, like rotational kind of, know what I mean? It's is consistant, like a steady bounce- not sporatic or itermittant. And like I said, this is just cruising at low speed down smooth fresh blacktop. Almost feels like a wheel/tire issue except that I don't feel any vibration or shimmy in the steering wheel. The tires are probably about 3 years old, but have less than 1000 miles on them. I had them balanced about two years ago.

WHatever is happening, it is definitely coming from the back, and must have something to do with whatever I messed with- the springs or shocks, because it didn't do this before. I also mounted my gas tank and battery back there under the bed at the same time I did the springs and shocks, but I don't think that would have anything to do with it.

You freed up the springs so they move as needed, the shock you have can may not be able to control the bounce. I would pull one off and see how much effort it takes to move it through it's range of motion. When you moved the fuel tank and battery, you shifted a lot of weight to the rear, this will also effect how the shocks work.

Hows the driveline angle, did you change it?

Mine runs smooth with the same basic set up, fuel tank behind the axle, tube shocks, and teflon spring liners. I also removed three leafs for a soft ride.

Joe

Probably a dumb question, but did you manage to mount the shocks upside down? I cured a bad-handling pure stock race car's problems by simply installing the shocks the right way. The car builder used a set of load-levelers, and mounted them the way they bolted on the easiest, which put the fluid reservoir on the top.
Jerry

Swap the tires front to rear. Sounds like an out of round tire to me. If the rear tires are out of round and you swap them to the front, you should be able to feel it through the steering wheel. Are you running bias ply tires or radial tires?

Here are a couple of pics of the rear shocks/springs. Let me know if you see anything blatenly obvious.

Pic 1

Pic 2

Tires are radial, by the way.

Steve,other than the lower shock bushes being at a slightly strange angle,to me the bolt should pass through at right angles to the shock body,everything else looks to be OK.
I don't think the angle would cause any more problems other than the lifespan of the lower shock bush.

Usually excessive bounce is down to 'dead' shocks,like JoeH mentions I would remove a shock and check how much resistance there is,as you've added considerably more weight to the rear of the truck,a full gas tank is pretty dang heavy!

When I did this mod to my Landcruiser , I had to buy superior quality shocks to tie the truck back down on the road. (I did both front and rear.)

The '40 has the same set up now and, again , I had to use much better shocks to keep it from bouncing off the road.

The spring pac now has much less internal friction binding it together , when you source shocks , try for something that has coils as standard springs. The valving for quality shocks for coil spring application is going to be different to the standard cart sprung truck.

ps, this is not to say that you don't have a tyre issue, perhaps you might like to swap front to rear as a test.
Regards

That all looks good to me, almost exactly like mine. Verify the pinion angle, swap the tires front <-> rear and see where you stand. If you get the same ride, go after the shocks.

Joe

The pinion angle is good, that was set up before I began. However id the process of disconnecting the rear from the springs, I wonder if one side could have shifted slightly forward or back. I did one side at a time, so as to not disturb things too much. If there was any movement one either sidem it would hve been minimal, maybe 1/8 at most. I'll rotate the tires amd throw the old shock on and see what difference that makes.

My Toyota Tacoma gets flat spots on the tires after a few days of setting, (Yokahama Tires). It takes two to three miles to round them back up, a few more when cold out.

Maybe give it a few more miles.

I think BigDaddy is right.

Stevebolt, Focusing on the statement of the "bouncing" being rythmic, not necessarily road surface related makes me think,like others said, the tires/wheels have out of round condition.
I have seen people fall into a trap allowing this condition when wheels were used that were not properly centered by the bore in their center which should closely fit a locating diameter on the axle or hub.
Watch this fit on after market wheels--the studs or lug bolts won't properly locate the wheels.
I would put the rear axle on jack stands or blocks with the wheels well clear of the ground-- crank the truck and make the wheels turn not very fast and look at the runout of wheel rim/tire od/wheel center hole.
I have seen bent axle cause what you are seeing.A bend in the axle shaft in the housing can make the pilot diameter and axle flange face for the wheel runout.
The condition could have been pre existing to your spring work but masked by percieved shock/spring problems.

Looks like the bottom shock bolt is in backwards. The smaller diameter stud is allowing motion in bushing - just like a worn spot on the shock would do. Make sure the bolt is a very tight fit in the rubber bushing. This also could explain the strainge angle the stud is at.