Why does it sway? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Blue'72 · 10-16-2006, 02:18 PM

I think I might have an idea what's causing this, but I want to get everyone's opinion. When I put any weight in the back of my truck and then get up to speed, any movement of the steering wheel will cause the back end to sway from side to side. The more weight and the faster speed causes it to sway really bad. It doesn't take a whole lot of weight, but it's downright scary when you load it up with firewood. Saturday I hauled two yards of bark in the back and pulled my trailer with three yards in it. The trailer was rock steady, but the rear of the truck still wanted to move from side to side.

I don't remember having any problems with my 72 half ton long bed I had a few years back. Everything's nice and tight under there, but I'm wondering if the overload leaf springs might be throwing it off somehow. The truck has coil springs and then some aftermarket leaf type springs that hold it up after the rear comes down a little. These overload springs only have one mount and the other end of the leaf sets under the frame to support it. (I wish I had pictures..)

Any other ideas???

**basketcase** · 10-16-2006, 02:26 PM

Does your truck have a front sway bar? Did your old truck have a front sway bar? Are the bushings in good shape? How about the bushings in the rear truck arms? How about the shocks?

I don't think it's the overload springs.

Blue'72 · 10-16-2006, 02:36 PM

I'm going to get under there and check it out better. I'll probably find some warn bushings I would imagine.

Other than the overload springs, both trucks are the same including the front sway bar.

67chevy2wd · 10-16-2006, 03:08 PM

I would check the panhard bar, runs from the axle housing to the frame. This is if you have a trailing arm suspension with coil springs.

**basketcase** · 10-16-2006, 03:11 PM

Also check over your steering parts for slop. This can have a big effect on how the rear moves when loaded.

neonlarry · 10-16-2006, 03:10 PM

Check the panhard bar very carefully.

OleBlue69 · 10-17-2006, 12:26 AM

My 69 does the same thing. How do you go about checking the panhard bar? I know what and where it is, but what am I supposed to be looking for?

Thanks,
Justin

67chevy2wd · 10-17-2006, 12:45 AM

The bushings, there is one in each end. How rotted they are, if they are still there. On my 69 the panhard bar is coming off the bushing on the diff. It is about half way off.

grayw0lf · 10-16-2006, 04:04 PM

Front sway bar? What is that?

Did all trucks ('70 Chevy C-10) have a front sway bar? Mine definately does not. But... I do have 4 wheel drum brakes.

Werewolf · 10-16-2006, 04:12 PM

It was an option on older trucks, I know. I've got one '68 that has nothing, and had one years ago, also with nothing.

see ten · 10-16-2006, 04:26 PM

I assume you have already checked the tire pressure front and back? Could you have a steering box problem that is being exagerated by the front end being lightened up (with the rear squatting)?

woodridge · 10-16-2006, 05:29 PM

Control arm busings and ball joints, a combonation of this and all the above. Just a little wear in each added up makes a lot all together.

stllookn · 10-16-2006, 05:35 PM

BTW, Those rear helper/overload springs are a stock option on these trucks. They should not be a problem.

Longhorn Man · 10-16-2006, 05:53 PM

Fill up your rear tires to max pressure, and see what it does.

RSRXION · 10-16-2006, 07:12 PM

How many plies are the rear tires? An insufficiently load rated tire will wallow around a bunch when loaded heavy. I'm betting that you've got a multitude of problems but I'd start with the rear tire rating , air pressure and panard bushings and mounts. JMHO, Dean

Brad · 10-16-2006, 09:42 PM

Travis, I'd check everything that was previously mentioned. If you still can't figure it out, perhaps another set of eyes might see something you missed. Let me know and I can take a look also.

*trkklr77* · 10-17-2006, 12:15 AM

i have always atributed that to side wall flex and leaf spring movement on my truck, as per i have 37" boggers and soft leafs[long truck]

tire preasure
panard bar bushings
shocks
front end bushings,
alignment

Blue'72 · 10-17-2006, 11:32 AM

Awesome guys, thanks!

The first thing I did when I noticed that was fill the tires, but they're crummy tires anyway and I'm sure that has something to do with it. I'm convinced now that it's a combination of a lot of things.

I think it's rather important and unsafe to drive as is, don't you??

Why, I don't think it would be safe to take my family in it for fear of something disastrous happening!

Ok, that's what I need to convince the wife about now and start thinking about putting some money into it! I think it would be a lot safer if it was lower to the ground too! Those stock wheels can't be helping any, and to really make it a safe ride, I should shorten the frame..

Well, I'll wish big anyway, and then the little things won't seem so painful on the check book..

Thanks Brad for the offer! We'll have to get together one of these days!

jamon8 · 10-17-2006, 11:43 AM

bushings are cheap and i would bet that yours, if not already replaced, are garbage.

Longhorn Man · 10-17-2006, 03:19 PM

Now I have no idea what a yard of bark weighs... nor the trailer you were using, but this also sounds like an improperly loaded truck. Were you overloaded? This is the 1/2 ton truck in your signiture right? What's the engine/gearing in it?

Blue'72 · 10-17-2006, 03:28 PM

It's a half ton, 350, SM465, 3:08 gears. I have to admit, a couple times I had it overloaded with firewood, but the first time I noticed it, I probably only had about 400 lbs in the back sitting just in front of the axle. I had more weight behind the axle one time and it wanted to sway without touching the wheel. Like a trailer will if the weight is too far back. I had to keep it below 40 mph. I need to get in there closer and see what I've actually got for bushings.

Longhorn Man · 10-17-2006, 03:48 PM

ok, with that description, you do have some issues.
Just for sh!ts and giggles (who came up with that term anyways???) your truck is only rated for a combined GVW (truck, trailer, and everything in or on them) of up to 6000 pounds. While we both know it can safely handle more, that is all it was made to do.
But if you had 400 pounds in front of the axle... then yeah...seriouse issues.

low'n slow · 10-18-2006, 12:21 AM

An improperly installed overload spring may actually cause them to bounce from side to side. It was not fun when it happened to me. Make sure the overloads are for your truck and installed properly. It is no fun to jack-knife.

jamon8 · 10-18-2006, 09:02 AM

how is it possible to improperly install the overload springs?

low'n slow · 10-18-2006, 10:26 AM

Most people wouldn't/couldn't do it wrong. I had a truck that the PO had installed a set on. I don't even know if they were correct for the truck. With a heavy load on the truck it would engage the overloads just enough to bounce the weight from one side of the truck to the other. I didn't keep them on long enough to experiment any further.

10-16-2006, 02:18 PM	#1
Blue'72 Skinned knuckles Join Date: Oct 2006 Location: Longview, Washington Posts: 1,126	Why does it sway? I think I might have an idea what's causing this, but I want to get everyone's opinion. When I put any weight in the back of my truck and then get up to speed, any movement of the steering wheel will cause the back end to sway from side to side. The more weight and the faster speed causes it to sway really bad. It doesn't take a whole lot of weight, but it's downright scary when you load it up with firewood. Saturday I hauled two yards of bark in the back and pulled my trailer with three yards in it. The trailer was rock steady, but the rear of the truck still wanted to move from side to side. I don't remember having any problems with my 72 half ton long bed I had a few years back. Everything's nice and tight under there, but I'm wondering if the overload leaf springs might be throwing it off somehow. The truck has coil springs and then some aftermarket leaf type springs that hold it up after the rear comes down a little. These overload springs only have one mount and the other end of the leaf sets under the frame to support it. (I wish I had pictures..) Any other ideas??? __________________ '72 C-10 longbox soon to be short step! '72 Chevelle (sold in January) '07 Sebring '01 Ranger (I've gotta long commute..) If you try to fail, and succeed, which have you done? My build thread - http://67-72chevytrucks.com/vboard/s...d.php?t=276904

10-16-2006, 02:26 PM	#2
basketcase Senior Member Join Date: Oct 2001 Location: Edgerton OH USA Posts: 633	Re: Why does it sway? Does your truck have a front sway bar? Did your old truck have a front sway bar? Are the bushings in good shape? How about the bushings in the rear truck arms? How about the shocks? I don't think it's the overload springs.

10-16-2006, 02:36 PM	#3
Blue'72 Skinned knuckles Join Date: Oct 2006 Location: Longview, Washington Posts: 1,126	Re: Why does it sway? I'm going to get under there and check it out better. I'll probably find some warn bushings I would imagine. Other than the overload springs, both trucks are the same including the front sway bar. __________________ '72 C-10 longbox soon to be short step! '72 Chevelle (sold in January) '07 Sebring '01 Ranger (I've gotta long commute..) If you try to fail, and succeed, which have you done? My build thread - http://67-72chevytrucks.com/vboard/s...d.php?t=276904

10-16-2006, 03:08 PM	#4
67chevy2wd Registered User Join Date: Sep 2003 Location: New Salem, ND Posts: 1,558	Re: Why does it sway? I would check the panhard bar, runs from the axle housing to the frame. This is if you have a trailing arm suspension with coil springs. __________________ 07 Chevy classic LBZ Duramax (a few mods) '67 Chevy 1/2 ton 2wd (in pieces) '69 Chevy 1/2 ton 2wd (on hold) '71 GMC 3/4 ton 4x4 ‘71 GMC 1/2 ton 2wd suburban

10-16-2006, 03:11 PM	#5
basketcase Senior Member Join Date: Oct 2001 Location: Edgerton OH USA Posts: 633	Re: Why does it sway? Also check over your steering parts for slop. This can have a big effect on how the rear moves when loaded.

10-16-2006, 03:10 PM	#6
neonlarry Registered User Join Date: Feb 2002 Location: Vacaville, CA Posts: 2,746	Re: Why does it sway? Check the panhard bar very carefully. __________________ 70 C/10 Light Red 350/TH350, HEI, Duals w/40 series Flows, 91 seat, LED taillights 99 Pontiac S/C GTP, SLP Ram Air hood, GMPP Konis & springs 95 Neon ACR, MP PCM, AFX UDP, 3.0 CAI

10-17-2006, 12:26 AM	#7
OleBlue69 Registered User Join Date: Dec 2005 Location: Collinsville, Virginia Posts: 26	Re: Why does it sway? My 69 does the same thing. How do you go about checking the panhard bar? I know what and where it is, but what am I supposed to be looking for? Thanks, Justin

10-17-2006, 12:45 AM	#8
67chevy2wd Registered User Join Date: Sep 2003 Location: New Salem, ND Posts: 1,558	Re: Why does it sway? The bushings, there is one in each end. How rotted they are, if they are still there. On my 69 the panhard bar is coming off the bushing on the diff. It is about half way off. __________________ 07 Chevy classic LBZ Duramax (a few mods) '67 Chevy 1/2 ton 2wd (in pieces) '69 Chevy 1/2 ton 2wd (on hold) '71 GMC 3/4 ton 4x4 ‘71 GMC 1/2 ton 2wd suburban

10-16-2006, 04:04 PM	#9
grayw0lf Registered User Join Date: Apr 2004 Location: Clanton, AL Posts: 1,253	Re: Why does it sway? Front sway bar? What is that? Did all trucks ('70 Chevy C-10) have a front sway bar? Mine definately does not. But... I do have 4 wheel drum brakes. __________________ 85' CUCV M1009!!! The newest addition! 6.2diesel, Th400, NP208, & only 36k miles! 70' C-10 LWB Fleetside - Looking good these days! 05' Dodge Neon 88' Winner Escape Sport 1750 - 4.3v6 94' Seadoo SP 84' Honda TRX200, bare nekkid. Just a frame & tires. Always looking for another project or any good deal!

10-16-2006, 04:12 PM	#10
Werewolf Woof? Join Date: Jun 2005 Location: Raleigh, NC Posts: 276	Re: Why does it sway? It was an option on older trucks, I know. I've got one '68 that has nothing, and had one years ago, also with nothing. __________________ 1968 LWB CST BB 2004 Avalanche Z71 LT3. 2003 S-10 ZR2 (hers). 1997 Astro 1992 Caprice wagon, 500k stock miles. Nursing wounds after a bad wreck. 1997 Saturn - need gas mileage from something!

10-16-2006, 04:26 PM	#11
see ten WTB this ad Join Date: Sep 2004 Location: Lafayette Georgia Posts: 5,074	Re: Why does it sway? I assume you have already checked the tire pressure front and back? Could you have a steering box problem that is being exagerated by the front end being lightened up (with the rear squatting)?

10-16-2006, 05:29 PM	#12
woodridge Senior Member Join Date: Feb 2005 Location: Maynardville, Tn Posts: 3,030	Re: Why does it sway? Control arm busings and ball joints, a combonation of this and all the above. Just a little wear in each added up makes a lot all together. __________________ SEMA Network- Protect our Hobby! 71 C30 in pieces, starting to come together. Click here for A Place For Tennessee Truck Enthusiest To Meet

10-16-2006, 05:35 PM	#13
stllookn Saving 1 truck at a time! Join Date: Aug 2001 Location: Kent, WA Posts: 6,465	Re: Why does it sway? BTW, Those rear helper/overload springs are a stock option on these trucks. They should not be a problem. __________________ '68 C20 Longhorn 50th Anniversary 400/TH400 '68 C20 Longhorn 50th Anniversary 468/TH400w/buckets '72 C20 Halfhorn (Longhorn w/o cab and front clip) '69 Flxible Cruiser (look up ugly in the dictionary)

10-16-2006, 05:53 PM	#14
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Why does it sway? Fill up your rear tires to max pressure, and see what it does.

10-16-2006, 07:12 PM	#15
RSRXION Senior Member Join Date: Jun 2006 Location: Arkansas Posts: 227	Re: Why does it sway? How many plies are the rear tires? An insufficiently load rated tire will wallow around a bunch when loaded heavy. I'm betting that you've got a multitude of problems but I'd start with the rear tire rating , air pressure and panard bushings and mounts. JMHO, Dean __________________ "They that give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety." Ben Franklin



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10-16-2006, 09:42 PM	#16
Brad Out of the carpool lane. Join Date: Jan 2000 Location: Clark Co, WA Posts: 5,673	Re: Why does it sway? Travis, I'd check everything that was previously mentioned. If you still can't figure it out, perhaps another set of eyes might see something you missed. Let me know and I can take a look also. __________________ 1968 C-10 SWB, 5.7 Vortec/700R4/3.73 posi, Torch Red 1968 Camaro, 250/Powerglide, all original (No, I'm not gonna drop a 350 in it!...Jeez!) 2000 Honda VFR in the faster yellow! 2008 Husqvarna TE-610 1967 C-10 SWB 'Six Appeal'-Gone but not forgotten...

10-17-2006, 12:15 AM	#17
trkklr77 Account Suspended Join Date: Aug 2006 Location: vacaville ca, because it as far from indy as i can be Posts: 777	Re: Why does it sway? i have always atributed that to side wall flex and leaf spring movement on my truck, as per i have 37" boggers and soft leafs[long truck] tire preasure panard bar bushings shocks front end bushings, alignment

10-17-2006, 11:32 AM	#18
Blue'72 Skinned knuckles Join Date: Oct 2006 Location: Longview, Washington Posts: 1,126	Re: Why does it sway? Awesome guys, thanks! The first thing I did when I noticed that was fill the tires, but they're crummy tires anyway and I'm sure that has something to do with it. I'm convinced now that it's a combination of a lot of things. I think it's rather important and unsafe to drive as is, don't you?? Why, I don't think it would be safe to take my family in it for fear of something disastrous happening! Ok, that's what I need to convince the wife about now and start thinking about putting some money into it! I think it would be a lot safer if it was lower to the ground too! Those stock wheels can't be helping any, and to really make it a safe ride, I should shorten the frame.. Well, I'll wish big anyway, and then the little things won't seem so painful on the check book.. Thanks Brad for the offer! We'll have to get together one of these days! __________________ '72 C-10 longbox soon to be short step! '72 Chevelle (sold in January) '07 Sebring '01 Ranger (I've gotta long commute..) If you try to fail, and succeed, which have you done? My build thread - http://67-72chevytrucks.com/vboard/s...d.php?t=276904

10-17-2006, 11:43 AM	#19
jamon8 Registered User Join Date: Apr 2006 Location: southern Il Posts: 335	Re: Why does it sway? bushings are cheap and i would bet that yours, if not already replaced, are garbage.

10-17-2006, 03:19 PM	#20
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Why does it sway? Now I have no idea what a yard of bark weighs... nor the trailer you were using, but this also sounds like an improperly loaded truck. Were you overloaded? This is the 1/2 ton truck in your signiture right? What's the engine/gearing in it?

10-17-2006, 03:28 PM	#21
Blue'72 Skinned knuckles Join Date: Oct 2006 Location: Longview, Washington Posts: 1,126	Re: Why does it sway? It's a half ton, 350, SM465, 3:08 gears. I have to admit, a couple times I had it overloaded with firewood, but the first time I noticed it, I probably only had about 400 lbs in the back sitting just in front of the axle. I had more weight behind the axle one time and it wanted to sway without touching the wheel. Like a trailer will if the weight is too far back. I had to keep it below 40 mph. I need to get in there closer and see what I've actually got for bushings. __________________ '72 C-10 longbox soon to be short step! '72 Chevelle (sold in January) '07 Sebring '01 Ranger (I've gotta long commute..) If you try to fail, and succeed, which have you done? My build thread - http://67-72chevytrucks.com/vboard/s...d.php?t=276904

10-17-2006, 03:48 PM	#22
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Why does it sway? ok, with that description, you do have some issues. Just for sh!ts and giggles (who came up with that term anyways???) your truck is only rated for a combined GVW (truck, trailer, and everything in or on them) of up to 6000 pounds. While we both know it can safely handle more, that is all it was made to do. But if you had 400 pounds in front of the axle... then yeah...seriouse issues.

10-18-2006, 12:21 AM	#23
low'n slow Too Dumb To Know Better Join Date: Nov 2005 Location: Texas Posts: 882	Re: Why does it sway? An improperly installed overload spring may actually cause them to bounce from side to side. It was not fun when it happened to me. Make sure the overloads are for your truck and installed properly. It is no fun to jack-knife.

10-18-2006, 09:02 AM	#24
jamon8 Registered User Join Date: Apr 2006 Location: southern Il Posts: 335	Re: Why does it sway? how is it possible to improperly install the overload springs?

10-18-2006, 10:26 AM	#25
low'n slow Too Dumb To Know Better Join Date: Nov 2005 Location: Texas Posts: 882	Re: Why does it sway? Most people wouldn't/couldn't do it wrong. I had a truck that the PO had installed a set on. I don't even know if they were correct for the truck. With a heavy load on the truck it would engage the overloads just enough to bounce the weight from one side of the truck to the other. I didn't keep them on long enough to experiment any further.

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