The Stovebolt Site Forums The Shop Area General Truck Talk jumping jehosaphat (bump steer)

When I drive down the road in my 50 Chevy 3100, I hit some road patch (fixed potholes) my truck will jump over the yellow line. This scares the oncoming traffic and myself, which might explain the foul smell in the cab. What can I do to fix this problem? Would a sway bar help? Is it a shock problem? (the problem of the jumping truck not the smell)

Please Help, Signed Scared and Stinky

Scared and Stinky in Michigan -

The problem you are experiencing sounds like "bump steer" to me. You will find a wealth of information on the topic by entering "bump steer" into the search window above.(include the quotes)

I hope this helps with both issues.

Sounds like it could be a combination of several things. I'd start with tie-end rods, and king pins and bushings. Might even take a look at the play in the steering box, if any, and even the wheel bearings although not likely.
Most can be checked by lifting the vehicle and grabbing the wheel top and bottom... and left and right..and then shake/pull on them up and down, side to side. Sometimes you can tell if tie end rods are bad by grabbing them right tight and twisting/wiggling them around.
Much has been said about the sway bars but I think most agree it does help.... especially on the panels/burbs but even without them you should not be having the problem you mention. I owned a 50 model several years ago and after the tie ends and the king pins it drove very well.

On my 58 the front spring shackles were worn enough to let the springs actually move back and forth.

Lose the bias belted 1950 tires, it isn't 1950 any more. That said, are you running bias ply? First priority, 100% brakes, thats new lines shoes, cylinders, master, king pins, wheel bearings. If you've done all the above and are still having problems more experienced will step forward with advice.

Thanks for all your info. I was able to put new tires on the truck. I went with 215/85/16 This made a huge difference in handling. I bought the truck with 235/75/15. These were balloon tires...

Next i bought the steering stabilizer. This made some difference. Next came the anti-sway bar. Roll is gone.

Next up is kinpins, tierod ends.

I still have some slop in the steering.

Sounds like you are well under way solving the problem. My '56 GMC Model 150 did that on the way home to Massachusetts from Long Island, NY. Turned out the right front leaf spring shackle was not attached. In addition, the left king pin was almost frozen. The seller told me it would not freeze up, just steered hard. I soon learned he was wrong and I was lucky. I have a deep respect for the leverage of that Saginaw steering gearbox!

Dave

I would have checked/replaced/rebuilt the kingpins, tie rods, steering box and spring shackles before putting on a steering stabilizer and sway bar.

My '41 GMC used to have the same problem. The fix cost me nothing but time. I suspect a lot of folks spend a lot of money changing a whole lot of things that aren't really necessary. Sometimes, we get caught in the way of thinking that old technology isn't as good as new, and that may be true on a few things but not as many as one might think.
Bump steer, wandering, or darting front ends were a bad thing in the 30's, 40's, and 50's and the design of the front ends is good enough not to do that IF it is lubricated properly.
I spent several days cleaning the old, hard, dried grease from my king pins, tie rods and spring eyes. This not only made it look better, but it made an escapement for the grease to flow all the way around the joints. If the the grease can't get out, it can't get in either. I had to remove the fittings and in some cases, I took a paper clip and dragged out as much old grease from the fitting's hole as possible. I made sure the little spring plungers worked on the tips of the fittings themselves, and I unloaded the joints by jacking the front end up with the jackstands on the frame...NOT... the axle. This allowed me to grease the truck properly for the first time in 50 years! When I pumped grease into the king pins, I heard a thunk...that was the grease filling the dried gap between the kingpin and its bore (yes, there must be a gap or in won't work). The same held true for the tie rods and the spring eyes. When I saw the same color grease exuding from ALL the way around the joints as was in my grease gun, I stopped and wiped the excess off. Sometimes, I had to wiggle the axle, tie rods, and springs to get the grease in and ALL the way around the joints.
When I drove the truck after doing this, I couldn't believe what I was feeling. The truck did not dart around when I would move to the shoulder of the pavement during a turn. It no longer wandered. It held straight down the middle and no longer had my nerves on end. It felt safe, solid and dependable again.
My theory is that with dry joints...kingpins, tie rods, and spring eyes...any jolt tends to make the joints stick into whatever position they are bumped into...in other words they can't tolerate a momentary jolt in a crazy direction and imediately return home. Proper greasing allows all the steering geometry to work like it was designed to work. Safe handling is not something that is new in this day and time. It was important in the 30's 40', and 50's too.
The evolution of the ball joint and better rubber seals made the old kingpin technology seem obsolete because the seal in the ball joint pretty much never allows the joints to go dry...and coil springs don't need lubrication...so it makes old technology look bad and obsolete.

So true ,ChetMan, So true , You have to spend the time doing all of thoes things that new trucks do not need , TLC , My Father would work on His car and truck keeping it lubed and looking good .


Pete

I agree with much posted.

verify all is well with the kingpins, shackles, tie rods and steering. Once your sure there is nothing worn, then lubricate.

Bump steer is simply a change in geometry when imparting a vertical displacement to one of the front wheels. If your suspension is in proper working order, the vehicle will track true. Bump steer happens with any suspension design if there is allowance by poor geometry or worn parts.

New suspensions are "lubed for life". Older suspensions need routine maintenance. They called them lube services for a reason, not just an oil change.