frame flex?

[rhagoki]

tracking down steering problem and noticed something today i don't think i ever have before.  when truck is running in park and you turn wheel all the way in either direction the truck seems to raise and lower respective to each side.  had someone turn wheel while i watched what was going on and didn't really see anything that looked obviously wrong to my untrained eyes.  Is this something that is normal and i never noticed or paid attention to?  its an 85 k10 running 31's.  I have a jeep with 33's and it doesn't seem to flex the way this one does.  Any ideas?

[1979C20]

Ive noticed this as well. I believe its because if you look at the tire, it rolls onto the corners when you turn the wheel. Like, look at the driver side tire, turn the wheel all the way to the left and youll see that its yilted a little and sitting on the outside corner of tge tire a little bit. So I think that raises it up a bit.

[bake74]

     The steering geometry has everything to do with what you described.  Lets say for this topic, your truck is stock height, with 31" tires.  If everything is tight (steering components ) and your steering drag link is level, then when you cycle your steering wheel back and forth, the front of your truck should stay level.
     Now lets say that on one side only you have a worn tie rod end, when you cycle your steering now, that tie rod end wants to give a little bit, so left it may drop, and right turn of wheel might raise it.
     So I would suggest that you have someone turn your wheel for you like you did, and really check each component in front for wear or movement, that would include things like bushing on your leaf springs and such also.  I know it can take some time and effort, but that is better than guessing and start replacing parts randomly.

[scorpion]

This is caused by the caster which is the angle of the knuckle in relationship to the ground.  Typically a stock differential has (I think) 4 degrees of negative caster which means that the top "ear" is rotated back 4+ degrees.  This is necessary for the return to center feel behind the steering wheel and changes the point on which the tire focuses it's weight during steering.  If you were to consider how the knuckle travels when rotated left to right, you'd see that the wheel actually rotates in a plane that is not parallel to the ground and, when turning lock to lock, you'd see the vehicle appear to tilt left or right depending on the direction you're steering because it's shifting from the inside of the tire to the outside of the tire.  It is likely that you would see the same thing on both trucks if you ran the same test with the same wheel/tire combo.  The larger tires are likely masking the issue by flexing at the sidewall as the weight is distributed between the center of the tire (tires centered) and on the outer/inner edges at full lock.

The relationship of a tie-rod to the ball joint centerline is called the ackerman angle.  It changes how the inner and outer wheel steer from lock to lock making the inside tire steer further than the outside when turning at full lock - which you may have also noticed at some point.  The ackerman angle, given the inner wheel turns more than the outer wheel, can also cause the shifting as the inner wheel's contact patch is further out on the tire than the outer wheel.  Larger tires that flex more at the sidewalls will mask this as well.

Add the two together and I believe that's what you're seeing.

[rhagoki]

I have replaced every tie rod, adjusting sleeve as well on the steering arm to pitman.  Ball joints are new.  I noticed when replacing the outer ends ( center link bar if im not mistaken )  the center link itself or adjusting sleeve as it seems to be called in haynes manual was slightly bowed.  Put it back on until i could research which center link type would be more durable ( both female solid bar with lock nuts on tie rod ends? or the long driver side tie rod that mates to adjusting sleeve then to passenger tie rod ) I'm sure it is causing some of the problem, but all the blame?  Im sure the springs have seen better days, planning on replacing all springs and related parts with softer ones as i don't tow much with this truck as soon as i get moved and actually have garage and room to work on it!

I do not have a factory service manual, any information on where to get one would be great  

As far as geometry is concerned what is the best way to measure the front end parts to be sure that they are perfect? any special tools other than i would assume a level and tape measure?  Im also assuming that those numbers/methods can be found in FSM. 

Any advice is welcomed, living in Dallas i don't wheel much anymore so my new hobby has become learning everything i can about this truck and getting her better than when she rolled off the factory line. 

[scorpion]

Can you describe the steering problem?

What I typically do is start at the rag between the steering shaft and the gearbox and work my way down.

Common Steering Box Problems:
Bolts that mount gear box to frame loose
Frame at steering box mounts cracked
Steering box loose & needs adjustment
Steering box sector shaft loose (what the pitman arm attaches to)

Pitman Arm issues:
Tie rod taper worn due to loose nut
Or just loose tie rod end nut

Drag link and Tierod issues really isolated to Tierod ends being worn or not greased and loose nuts or warn tie rod taper holes in the knuckles/tie rod.

Knuckles, for the most part could only be ball joints.

Loose or worn out wheel bearings can add slop and not be very noticeable if barely loose.

It's a stack problem.  You could be looking for 1/16th of an inch slop in 8 places which totals up to 1/2".  Usually you'll find a smoking gun that makes things good enough to stop looking.  Other times everything needs service.

[scorpion]

Oh and leaf spring bushings can add to the slop.  Check the four in the springs and the two in the frame to the rear. 

That's really all I can think of. 

[Sodium Duck]

Great info.

[rhagoki]

Never thought about taper being worn, thanks for all the info!

The front end feels really loose in general.  Pulls slightly to the right and even the smallest bump or uneven roads makes the wheels feel like they're just rattling.  Re tightened all bolts nuts etc and its helped with getting the steering feel not so loose.  The wheels still seem to feel not right. Not sure if its more of a bouncing or a wobble im feeling,  gonna drive it a little more now that steering feels better to get more of a feel. I know the shocks are garbage, was waiting to do everything else up front before putting them on

[scorpion]

Sounds like you may have more than one thing going on.  When you're driving straight down the road, how much can you move the steering wheel side to side before you actually get the steering to respond? 

Rough road handling is tough to diagnose because more than just the steering is being jarred by the surface.  Uneven roads play tricks un us because natural tire pull can cause the steering to jump even when things are in good working order and it's made even worse if you're running larger tires.

Take a look at your shackles at the rear of the front leaf springs.  If your leaf springs are worn and sagging a little, the eye of the spring can come in contact with the frame on compression (and sometimes at ride height).  If this is at the case, and your bushings are worn a little (or a lot), you'll get a lot of noise and vibe transferred to the cab.  Many springs have leaf keepers that keep the leaves in alignment with each other.  A loose keeper will make noise on spring compression.  Also, springs have noise reducers between the leaves (they may be stickers or plastic looking pads).  If one is missing on one side, it may create noise.

Do you have a steering dampener?  Check the attachment bolts and make sure it's in good working order (as a shock absorber should be).  They are typically attached to the diff with a welded on bracket and to the tie-rod with a series of small u-bolts.  You can also check to make sure that when the steering cycles, the shock isn't hitting something.

It's not always possible but sometimes you need to drive a friend's rig that's similar to help figure out what's normal and what's not.  The easiest way to start, given your feedback, is to attempt to reign things in on flat even surfaces and get it so the steering is tight and well behaving there. 

[malibu795]

frame flex was part of the design and it sucks!
no boxed part of the frame, severly weak crossmemebers been working on stiffing up my turck