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The death wobble....


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Happened on our 1928 Pontiac after hitting a bump in the road a few day ago. Car had been restored over 10 years ago with little mileage at all. First time its happened in our caretaking. Hadn't noticed anything prior except the steering box play.  I have experienced this in a old dodge ram, and it scares the ell out of you.....

 

Steering box has a lot of play and I don'.t know what else yet. What is involved in taking up the play in it?

 

Thank you!

 

Mike

 

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Seems to be a topic people have 500 opinions death wobble.  

 

I take my cars (and he has done from brass cars for me to 60's cars, but mostly 30's CCCA cars) to Performance Alignment in Cincinnati, OH - http://performance-alignment.com/  Bill Braucksick is one of the more respected people in racing and in using a Hunter System (a good engineering mind).  And, the price is usually reasonable, but I would not say cheap.  And when they run into problems with worn out stuff they always have the solutions though you end up in a time crunch and have to be on your toes to respond (aka your car will not just be sitting around their shop waiting on you for a whatever).  

 

And, I have had 100's of people tell me that this advice on this is not worth s_ _ t and they are going to do it themselves and they know what they are doing. 

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Death wobble is an easy fix.........all you need is MONEY! Just do everything from the king pins to the steering box. There is NO shortcut. Also, correctly align it......another can of worms. Too many people look for the easy way out and just try and fix one item........it NEVER works. Yup......it’s going to take time and money, no way around it.

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Try an alignment first. It worked well for my 1931 Dodge. Someone had installed two extra shims on the axle/leaf spring assembly and the extras were broken. Removed those, aligned it and no more death wobble.

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Before the alignment:

 

* you may have adjustable tie rod ends--look for slop and adjust.

 

* Drag link aka reach rod:  Open both ends, carefully, look for broken spring(s), inspect the ball studs for wear, clean out all the nasty gunk.  You can mark the end of the ball studs so that they can be installed with the unworn portion in the loadbearing/wear position.  This gets a bit tricky, and requires needle nose visegrips on the stud to keep the unworn positions on the ball next to the concave half-spheres.

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Every thing that Grimy and edinmass say.

Make sure to check caster, camber and toe-in as well as all the adjustable ends.  Visual inspection of the ends is not enough.  They should all be taken apart, worn cups and/or broken springs should be replaced, and adjusted properly. Adjust the steering box.  Check all spring shackles (4) and the solid spring pins (4).  Also check that the car sits level when on a level surface.  One or more springs may need to be re-arched.

All of my Pontiacs '26-'31 would cruise down the highway dead straight with hands off and my '30 (daily driver for 59 years) would even go across a  railway crossing hands off at 60 mph.

Do it right once and that will last at least 50 years in my personal experience.

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As mentioned by others any front end looseness (coupled with out of true wheels )can really set things in to scary motion..

Not a fix ..but I have stalled off or reduce the accurance and severity of death wabble on teased out old cars(1920s)TEMPORARILY ,caused by very bad king pins and shot tie rod bushings by refitting / mounting the demountable rim and tire on the spoke rim for better trueness and then slightly widen or open the toe -in from specs so you plow down and grip the road a bit which may cause a bit of wander effect to a degree but atleast you don't have to stop the car completely to a halt in the middle of a 4 lane bridge because you can't turn the steering wheel once the racking starts..! Thats death wobble!

Winter is almost here! Rip off the front end,get it in the basement and go to work 👹

 

 

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In addition to the excellent prior responses, tire pressure can also be a factor, along with wheel bearing slack.

To be safe, start at one end of the steering system, and work your way through to the other end.

Replace, repair, readjust, and don't "cheap-out", since MY life may depend on your repairs :rolleyes:

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There is no short cut for the death wobble........just go through everything.....it’s easier in the long run. And the car will steer much better also. No down side to doing it right.

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Check EVERYTHING.

 

Clean out and repack your wheel bearings and adjust them correctly. Check for kingpin play while it is up in the air. Many old cars need kingpin work. It's one of the first things to go. If they're OK, give them a shot of grease because they always need one. Spin the wheels too and make sure they (and the tires) are straight and round. Balance if possible.

 

Make sure your steering box is full of appropriate lube (Penrite's might be about right for a 30s Pontiac, but check the manual). Adjust the steering box according to the manual. Rebuild if it won't adjust.

 

Check all your tie rod ends, clean out and adjust. Replace any balls that are oval and causing slop when the car is pointed straight ahead. Regrease.

 

Align the front end to the factory specs. If there's no shop that specializes in prewar stuff, go to one that does heavy truck, bus, and motorhome. Why? Because if camber is off you most likely set it by cold bending the axle, and a modern car shop wont have the equipment or know how. Toe is set by the drag link and caster is set with tapered shims (another thing only a truck outfit will have).

 

Inspect your shackles for wear, stuck bushings, and slop. Grease any that have fittings. If they won't take grease, take them apart and find out why.

 

Straight axles were prone to death wobble, and it is one reason they aren't used much anymore. The engineers of the time knew this of course and didn't send it out the door when new doing that. If you get rid of the slop and use their alignment specs it will be fine. Good luck and let us know how it goes.

 

 

 

 

Edited by Bloo (see edit history)
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12 hours ago, Delco32V said:

What is involved in taking up the play in it?

 

 

This changed every couple of years back in the 30s and varied by make and model. If you don't have a shop manual for that car get one and do exactly what it says. If you don't know where to get one (maybe Ebay?) send KornKurt on this forum a PM and ask. He has parts. If he doesn't have the book he probably knows who to ask. California Pontiac Restoration is another possibility.

Edited by Bloo (see edit history)
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I realize the picture I am posting is for a Series 6-30B.  However the descriptions of the parts is the same From P6 to 1932 even though the specific parts are different..

Therefore I assume rightly or wrongly that the adjustments are similar.  I used to have Parts, Shop and operators for all of my split head Pontiacs but always included the books when the car was sold.  I would suggest that you invest in all three.

I do hope this helps.

DSC03241.JPG

Edited by Tinindian (see edit history)
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On my 1933 3 window Chevy coupe Street Rod, I had it happen one day with a friend along.  I had just put new king pins and tie rod ends.  I had adjusted the steering gearbox and all was well.  The wobble started at around 35 mph.  It had done it before and if I sped up it went away.  This time the car shook so bad, we could NOT even see out of it!!  I hit the brakes and my friend wanted to walk back to town!!  I took it to an old shop and asked what might be causing it.  He told me to remove the old lever shocks and put regular shocks on the front axle.  I put a pair of  Dodge pickup truck cast iron braces on it and new regular shocks and it never did it again.  At the Cordova drag strip it ran 101 mph in 14 flat with not a quiver.  I have a friend that had a 1975 Chevy dually that he never could get the wobble out of.

I was doing front end alignment work at the Chevy garage in Sterling and never ran across it there.

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Check to see if they put the caster shims back in when they resembled the front axel (backwards would also be bad).  The wedge plate (silver).  My 1928 Graham-Paige was missing them when I got the car, death wobble at any bump over 25mph.  Installed the caster shims and no more problems and no steering shimmy even at 50mph.

 

Caster shims; which direction?? - The CJ2A Page Forums

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Had it on a new hunter machine which is very sensitive. Its actually not bad with the exception of worn king pins, so new ones have been ordered.

 

Its a I beam front axle, so no caster adjustment save for bending it, but its OK. The slop is the king pins. Toe was OK too. 

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Caster shims almost always fix death wobble..........as long as the front end is tight. I keep them in stock in the shop..........I use the old fashioned alignment heads and turn plates, as I find trying to put modern alignment machine heads on old cars is almost always difficult to impossible. Also, for the cost of three alignments, I can now do all my cars in house.......and I am sure I am fussier than most of the young guys at the shops today.

Edited by edinmass (see edit history)
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I am not an alignment specialist but if I understand it correctly all vehicles with a straight axles use caster shims to get the 1.5 to 3 degrees of caster needed to make the front wheels track correctly.  The caster also helps the steering wheel return to center, if you do not have enough caster when you turn a corner and let go of the steering wheel it will keep turning, instead of wanting to return to driving in a straight line.

 

image.png.990b44bc837c2d86ce2ae6e3c50f537c.png

 

Caster Angle Explained video

 

 

Edited by Graham Man (see edit history)
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Graham Man, you are correct.....but removing castor stops death wobble..........and added castor returns the wheel to straight when you release the wheel......like a power steering return. With todays roads, we put castor down to 1/2 a degree. It causes some more steering effort......but it eliminates death wobble. We recently had a car that had a steering dampner on it for fifty years due to death wobble.......I pulled out the shims that were 2.5 degrees and took it down to .5 and the wobble was gone, and I removed the damper. Alignment, air pressure, front end components worn, and modern tires all make each case different. General rule of thumb on BIG pre war cars is 45 pound pressure in front tires, 1/8 inch toe in, 0.5 degrees castor. Check ride height, spring condition, and shackle pins. It's a big picture repair......shocks should also be serviced. I think front end/steering box/suspension is one of the most overlooked areas of drivability issues on cars today. Many people don't know how a car should steer and stop, and thus they think all old cars steer hard and stop poorly. The exact oppisite is true. It's my experience very few cars steered poorly. It's 100 years of wear, lack of service, and other issues that cause cars to perform poorly. 

8AAA4012-F356-4D25-88FB-A1697862DB71.png

Edited by edinmass (see edit history)
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9 hours ago, Delco32V said:

Its a I beam front axle, so no caster adjustment save for bending it, but its OK. The slop is the king pins. Toe was OK too. 

 

It is camber that requires bending on straight axle cars, not caster. You won't know much about the camber until you do the kingpins as the kingpin slop will make the camber measure more positive. Keep us posted.

 

 

Edited by Bloo (see edit history)
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I have tried to run 45psi in my tires but they seem to "bounce" at that pressure, roads by me are not perfect, I tend to drive on the 45-60 mph side (live out of town).  Lately I have been running around 36 psi.  I have gravel roads to cross so it is easy to check tire contact patch, anything over 36 and it starts to lift the sides of the tire contact area.  I have not been able to find much supporting vintage evidence for tire pressure setting in the early 1930s cars.

 

Under-Inflated Tires Cause Additional Fuel Consumption | Top Speed

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In an old car, your concern is NOT tire wear, it’s safety. Air pressure I quoted was for balloon tires that run from 1929 to 1938 give or take. Aspect ratio, wheel size, year, maximum speed, and a bunch of other things come into consideration. 

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I like that chart.

When we were racing I would often have a crew member shoot the  temperatures across the tread faces after a good hard run.

This way we could calculate pressures and camber for a possible better set up.

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