Left-turn snapping noise - Ideas??

[SkinnyG]

'77 Silverado, 350/th350.

There is what sounds like sheet metal being caught in a driveshaft, but only when I turn moderate to hard left turn only. Only there is no sheet metal in the driveshaft.

I ~think~ I can feel it in the steering, but I might be fooling myself.

Usually sounds like it is coming from under the floor, other times it sounds like the front wheel area, and sometimes from the rear axle area. Not at all useful, I know. It also seems to be related (or more easily instigated) by bumps on the road.

Here is what has been done, not all related to chasing the sound - just what has been done, none of which made a difference:

350 fully rebuilt
2500-stall converter added, "tamed" B&M shift kit, fresh fluid
Headers, x-pipe, and dual exhaust installed
Heat shields removed (cat is gone)
Poly engine and trans mounts
Poly cab mounts
Poly suspension bushings (front and rear)
New 1-ton coils
BellTech spindles
Upper a-arm bolts checked for tightness
Lower a-arms moved forward 3/4", cross member rail clearanced
Flip kit, both via bracket and via welded spring perches
New U-bolts
Rear shock extenders
New shocks (front and rear)
Box mounts inspected, bolts replaced
Rear brake drums turned to remove any corrosion on the edges
Front hubs cleaned and bearings re-packed
Fuel tanks removed and truck tested to see if they were contacting anywhere
Control arms trimmed for wheel clearance
Fenders checked for tire clearance
Front brake calipers and dust shields checked for clearance

I cannot find any contact at all anywhere.

Another funny thing, is sometimes it is worse when cruising around 35mph in 2nd, even on the straight.

It is also usually much worse when pulling my utility trailer.

Honestly, I'm not sure where to look, and I'm hoping someone might have some magical experience like this and might know what tree I need to bark up.

Thanks.

[Dead Parrot]

My 75 does something similar except it isn't turning related. Various speeds and throttle inputs will cause a loud rattle that from the driver's seat, seems to come from the front most of the time. Sounds like a metal on metal fast rattle.

Suspects were the wires going to the starter, the manual choke cable and various hoses. Moving and securing those had no effect.

While replacing the heater core, I found that I could make the noise quit by pushing on a few magic spots on the passenger side floorboard. Decided I had enough of a project with the heater core and left well enough alone. I know there is some rust damage in that area so a future project involving seat and carpet removal is on the agenda.

[SkinnyG]

Interesting. I may screw with that on the lift at work.

The floors on this truck are very solid. No rust at all. But I shall give it a go and see.

[rich weyand]

Check that the frame isn't cracked at the steering box. Common problem on K trucks, can happen on C trucks. You could be snapping a broken edge past the other edge of the break and back. There is a plate you can buy that welds in place to fix this.

[SkinnyG]

I had looked previously for cracks on the inside (didn't take the steering box off), but didn't see any. That thought had crossed my mind - it makes sense.

Last night I removed the sheet metal torque converter metal, though I suspected that couldn't (shouldn't) move enough to cause a problem. No fix.

I also rotated the front coil springs such that the tops were locked into their cups, and the bottom ended up where the bottom ended up. Previously I had the bottoms seated, and let the top end up where it ended up. This has resulted in the LF coil spring precariously close to the front of the spring pocket in the crossmember. No difference.

BUT!

After last night's test drive, I happened to notice a small stone (~3/8") sitting on the top of the steering box against the frame. I couldn't flick it out of there with my finger, and it took some abuse with a screw driver to pop it free.

Could this be it? Makes sense - the noise is not consistent with road speed or engine speed, but might be with flex. I'll find out on the way to work this morning.

Golly I hope so. I've been chasing this for over a year.

[Rich84]

I had a broken leaf spring that caused a similar noise..It was cracked at the eye.

[J Knight]

If removing the rock doesn't fix the noise check the bottom rivet on the drivers side that hold the front crossmember to the lower frame flange right below the steering box. I have seen the hole get woddled out and the frame will move against the crossmember making a squeaky popping noise. Have someone turn the wheel back and forth while you're under the truck.

[SkinnyG]

Well, the rock didn't fix it.

I was able to make a similar sound by wiggling the left side e-brak cable eye hook thingie, so I moved it to a different hole where I could not replicate the sound. But that didn't fix it.

I took a super good look at the steering box bolts on the inside of the frame, but did not see any cracks or any evidence of cracks at all. I did not remove the box.

I didn't see any cracks at the leaf spring eye when I did the bushings last year. I shall look again more closely.

I will also take a look at that rivet. Hadn't thought about that.

[greg64]

Skinny, I didn't think the frame on my c10 was cracked at the steering box either. I discovered this when replacing the steering box. Now, I'm not saying this is definitely the cause of the noise, just that you can't always tell with the steering box bolted up.

Do you have to be moving for the noise to occur?

[SkinnyG]

Today I removed the steering box and had a good look. No cracks.

It only makes noise when moving, and when turning left. More g-force related than steering angle related, and it is exacerbated by bumps.

It ~totally~ sounds like sheet metal being fed into something spinning. Is there anything that could do that in the transmission, or in the power steering pump?

In the mean time, I found this:


That can't be good....


Nope. Not good.

Didn't fix the noise, but the "lifter ticking" went away.....

[jdf915]

Maybe some thing hitting the fan?
Posted via Mobile Device

[SkinnyG]

Fan is electric.

Hmmm.... I need to pay closer attention to whether it is engine-speed related, or road-speed related.

[greg64]

Skinny, I've heard a noise like you're describing when one of the flex plate bolts fell out and was trapped by the dust shield. Turning may be scooping the lose bolt up and kicking it around inside the bellhousing.

[SkinnyG]

For sure there is nothing there.

I am currently (as of the weekend), running without the shield at all.

Having ~just~ changed the flex plate today after work, I know for a fact there is no contact of any kind of any part inside the bell housing. No clean shiny metal, no shavings, nothing even close to anything.

I even dragged a "magnet on a stick" through the bottom of the P/S pump to see if a bolt had fallen in there.

It's noisy like "OMG WHAT THE HELL IS WRONG WITH YOUR TRUCK, MAN?" loud.

And this is why I am so stumped. The horrific racket should at least be a visible and significant issue.

Can't find it.

[jdf915]

Did you ever get this fixed? Had an idea the other day, what condition are your motor mounts in? If one of them is loose enough the motor might shift enoough and run the cooling fan across the fan shroud. Just a thought.
Posted via Mobile Device

[SkinnyG]

No fix yet.

Since I posted this, I have installed a c-o-m-p-l-e-t-e-l-y rebuilt 12-bolt with all new everything and a different housing, so I can rule that one out.

I'm suspecting maybe something wrong with the left leaf pack, but all the leafs seem tight and solid. If I'm feeling adventurous, I may swap leafs left to right and see if the noise follows. But still, it's a "feeding sheet metal into a spoked wheel" sound.

I bought a power steering pump rebuild kit to go through the pump in case something is inside there, but I haven't gotten around to it.

The motor mounts are poly and near new, and the fan is electric, so that isn't an issue (post #11). It did it before the mounts were changed, and before the exhaust was built.

[Axle]

Since all the common suspects seem to be rulled out, back to sheet metal; Inner fender movement? How are your front (rad cradle) bushings?

Do you feel anything in the steering wheel when it happens?

Alex.

[SkinnyG]

All cab bushings are new, rad mount bushings are new, all suspension bushings are new.

I can feel it in the steering, yes. But it kinda sounds like it's coming from behind the cab (doesn't mean it is - it sometimes seems like it's coming from up front). Something in the rear suspension could affect the steering.... No parts of the front control arms are close to anything.

I have checked front wheel bearings, clearance to dust shields, and the control arms are well clearanced for the 15" steelies. I even tried 1/4" spacers just to see if I was missing something - no difference.

I went through all the sheet metal in the box, including the mounts - all the carriage bolts are new, and are securely tightened. The shields/flaps and whatnot around the fuel filler are sound.

I actually was thinking about the front inner fenders today - they are solid (I patched all the rust holes), and I believe they are securely fastened, but I may go through them tomorrow and check. I did NOT, however, replicate the reinforcing triangle what sits right behind the front wheel where they always rust. I merely patched the holes (both left and right sides).

It does it less if I am turning left and accelerating hard, but it still only does it when turning left.

[jdf915]

Can we get a video?

[enaberif]

If it does it turning left I would be looking at the right side instead. This sounds something similar to when a cv joint goes bad.

When you go around a corner the clicking is usually the opposite side due to weight shifting more to the outside wheel.

[68c10owner]

This may not be the noise you hear but years ago I had a noise on my 75 gmc only when I turned one direction, can't remeber which way. Turned out to be the front brake pads. One side was down to the rivets and when the force of the truck pushed the wheel the rivets would rub the rotor. Didn't do this when applying brakes, only when turning. Replaced the pads and it went away

[Gmc.guy]

I had the same thing on my 74. It would chatter and ping and drove me nuts trying to find it. It wouldn't do it all the time while turning, just sometimes and once in awhile at slow speed going straight. I could feel it in the steering wheel. It turned out to be loose bumper bracket-to-frame on driver side beside the steering box. (the hole is slotted) loosened off a bit or were never tightened. Might be worth taking a look at

[Axle]

Originally Posted by enaberif

If it does it turning left I would be looking at the right side instead. This sounds something similar to when a cv joint goes bad.

When you go around a corner the clicking is usually the opposite side due to weight shifting more to the outside wheel.

Sounds like you have been fairly thorough SkinnyG. enaberif post got me thinking front wheel bearings. You did say repacked, but have you gone back and retightened the castle nut to see if any new slack showed up from something that may not have been fully seated initially but made initial bearing set feel right?

Have you greased up the steering stops on the lower control arm? (left side in this case). Look for a shiny spot on your lower control arm with a concave shape. Smear a glob of grease on that point and go for a spin.

Alex.

[SkinnyG]

I hosed the bumper bolts today with penetrant today so they might move tomorrow. I've previously installed pushers on the front bumper, with freshly chased threads and never seize, so those are for sure good (no difference after the install). I'll check the outer bolts and mount extensions tomorrow.

I have not gone back to the castle nut, because I seat the bearings like a MoFo and then set the bearing properly. I've never had to before, but I can give it a look see. After packing the bearings, I later took everything apart and thoroughly inspected the bearings, cage, races, and looked for any contact with anything, and reassembled and re-set. Still noise. Even later pulled it apart and changed the dust seal (just because I now had some), and re-set.

The steering does not have to be at full lock. It depends more on the g-forces, which still makes me think suspension, or even the flexing of the frame with loose bumpers makes sense. It did it with no bumper on the back, and was no different with a hidden hitch and a bumper installed. Had a Nissan Hardbody that made a nasty GROINK! at full lock, and you're right - grease to the rescue. But that's not what's happening here.

Is there any logical reason why an inner fender might do this?

Thank you all so much for your help in this, I can't wait to solve it.

[83 Silverado]

Looking at some of you post I don't see any mention of the steering assembly parts, mostly the idler arm. If the idler was worn and had some deflection under load, any tire scrub vibrations may get transferred in to the frame on a turn. I'd like say I had this on one of my trucks.