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Bump steer/death wobble

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33K views 161 replies 27 participants last post by  1971BB427  
#1 ·
Hi everyone. I thought I had my bump steer/death wobble problem fixed. The steering was good for a very long time. Today, I took my '56 gasser out for a ride for about 20 miles. Again no problem until I came to a stop sign and had to make a hard left turn onto the road I live on. Made the turn and started up the road. Was going about 20-25mph and OMG, the death wobble started all over again. I didn't hit any bumps or holes. I couldn't believe it. Thank God I was only a couple hundred feet from home and I was able to back it down the driveway. I looked underneath and didn't s anything of interest. I don't have a clue as to why this happened. Had the car up to 60-70 mph several times without a problem. It tracked very straight. During travel, hit minor bumps but still no problem. I also made other hard left and right turns with no problem. I might also add, that the stock steering box on this car is shot. There is absolutely no adjustment left. You have to constantly correct the car going around even slight turns. By correcting, I mean turning the steering wheel a decent distance. Any ideas why this suddenly happened?? Would this bad steering box cause this or at least contribute to it?? I'm open to any and all suggestions. Thank you, Carmine.
 
#101 · (Edited)
i got some 990's in the garage, technically on the big side, but, i got them for a good price. 200 hundred bucks stock...so i couldn't pass. when i'm done playing with this tunnel ram 427. i might go to a huffer one day. so far i've ran, a stock 350 with an rv cam, a 305, a 355 cammed up with camel hump heads, the 454 i got now, and finally to the this little rat. i suspect i'll go with a 496 with some 6.5 rods or so, after this 427. the cam cover in the photo is just a regular aluminum cover from a swap meet, got a gear drive for it. solid lift .560. it's going to be a toy that i run at the track from time to time and drive around town. i'm still debating whether i want to go with 3.73's or 3.89's with the doug nash or keep the 3.50's to go to local car shows...local meaning up to 40 miles away. it gets like 8 mpg's right now with the dart intake and the 188's or maybe they are 088's on the 454.
 
#100 · (Edited)
Bob ,
I believe I have always found the motor build the most interesting of
what ever auto project I'm involved in , that's a swell fat block Chevy
you have going together , do I see an Erson 3 gear cam drive or
similar there ? I am using one on the 496 that's planned for my
56 , slow going but it WILL get done !! The high rise is an impressive
deal sticking up there but have you ever considered a blower , they are
not that expensive any more and are not at all as scary as you might
think to set up and run and once you learn them you got it whipped !!
And you will never go back , Ha Ha !!
What heads do you have planned , iron most likely , you already have
the studs stuck in there , I found out that the Dart Pro 1 heads need a
longer set of studs , part of the learning curve , like why didn't someone
tell me , Ha Ha !!!
Have fun Bob !!!

easy

( click on the gif , it's fun )
 
#99 · (Edited)
here's a picture of my sweet little baby rat 60 over 427 (just like the one dear old grandpa would roll in his stock 216 sedan hotrod). lil old ladies find it the just the quaintest autobile to get groceries in. it's like i'm driving an electric car it's so quiet to them (without hearing aids), you never feel the road kill with the truck suspension it has. (cuz its a tank) and most everybody waves and smiles (cuz they've never seen anything like it). just a nice old classic automobile, usually on a sunday afternoon after church, i go down to get a fountain drink at the local malt shop. (gassing up, before and after) if i would change anything i would make it purr just a lil bit to let everyone know it has a lil something under the hood (no hood on this one anymore)

Image
 
#103 · (Edited)
here's a picture of my sweet little baby rat 60 over 427

Image
If those are ARP studs in your 427, you should test fit the heads and headers! I got them for my 464 and discovered AFTER torqing them down that my header flanges hit on all the bolts along the bottom edge of the heads! I couldn't get my headers to seal up against the gasket because ARP makes the stud too long, and with the excess stud sticking so far up they hit the flange.
I had to take a parting wheel on my die grinder and carefully cut them flush with the nuts. I still had to also grind on my header flanges a bit also, as the nuts on the ARP studs were taller than head bolts, and needed more clearancing to fit. Was a little unnerving to have to grind around my new aluminum heads, but fortunately I didn't slip and hit them!
You can see in this picture how far the studs and nuts stick up before trimming. A good thick flange will definitely not clear under the exhaust ports!
 
#93 ·
57 with straight axle and front steer the steering box is right under the radiator with no oil pan or bump steer issues. I have a 55 project in the works with an Econoline axle and front steer setup also. The drag link is parallel from side to side and front to back. All Borgeson steering shaft parts and axle set at 8 degrees.

Image
 
#95 ·
57 with straight axle and front steer the steering box is right under the radiator with no oil pan or bump steer issues. I have a 55 project in the works with an Econoline axle and front steer setup also. The drag link is parallel from side to side and front to back. All Borgeson steering shaft parts and axle set at 8 degrees.

I really like those valve covers. Would you be willing to chuck out the brand name of them, or is it top secret? If so I understand.
Dan
 
#79 ·
So a tunnel through the oil pan isn't a bad idea either, I used to make aluminum pans with tunnels for hemi roadrunner super stock cars when I worked for Dave Benjamin a LONG time ago, lol.
 
#77 · (Edited)
I just had to add my 2 cents. While the op's car obviously has some type of geometry problem that he needs to work through, to write off the whole idea of a straight axle front end on a Tri-Five as something that won't work on the street is crazy. Look under any school bus, medium or heavy truck, Jeep CJ, etc. and you'll see straight axle technology that is still being used today and logging many, safe, miles.
 
#76 ·
You are quite correct. But there are ways to make the best of it. The "death wobble" wasn't part of a good drag car suspension back then, still isn't. Same with bump steer.

My thought on mounting the steering box is to turn the sector shaft to horizontal and orient the pitman arm vertically. Then run a link forward, keeping it horizontal at ride height. Then turn the lever on the steering knuckle so it's crossways to the length of the car. Like many 30s hot rods use.

Or you could put the box further forward like classic gary suggests, using u-joints and a two piece steering shaft. (Three piece if necessary like many R&P installations use.) Then use a cross shaft and connect it to the passenger side. Depending on where the box ends up, the pitman arm is either forward or backward. You may need a reverse rotation box depending on the pitman arm direction.

I don't think that a panhard bar is necessary with the parallel leaf springs, unless your components allow the excess side to side motion that's been discussed.

In the end, it's all in the details. But there's more than one basic layout that will work.
 
#75 ·
For all the guys on here that are desperately trying to make
an old outdated drag race deal work on the street , the high
in the sky straight axle idea was to go fast down a drag strip
and transfer weight to the rear for inhanced traction period .
You will never make this deal happy and fun to drive on the
street , it was never intended to have that function !! You
would have a better handling and more fun car to drive by
just putting a set of gas shocks on your stock Tri-five
suspension . Believe me , I tell the truth Kemosabe !!

easy

( the happy wabbit )
 
#74 ·
You could put the steering box in front of the axle. A couple of u- joints, some steering shaft and a box mount. You've got the stock front sheet metal? It'll take some imagination, but It could be done, I think. Or notch the oilpan, that was how it was done back in the day.........
 
#81 ·
This is the perfect solution. I'd never want to remove that old W motor in your gasser! It's just way too cool to not do whatever it takes to retain it! I had the same problem you have when I dropped the 464 BBC into my '63 Falcon, and realized the oil pan was right in the way to steer off the back side of the axle!
I simply mounted the steering box in front of the axle, and flipped the pitman arm 180 degrees towards the axle. Then a drag link across to the top side of the pass. side backing plate. It made the install easy, and only required a joint and DD shaft to adapt to the forward mount box. The drag link is so level that it has zero bump steer and clears the oil pan easily.
Since you need to replace your steering box anyway, I'd suggest trying to find a late 70's Courier or Mazda truck box, as they are tall and will place the input shaft above the frame rails, but the pitman arm below the frame rail, and make the swap much easier.
As you can see in this old picture from my build, the Courier/Mazda box sits outside the frame rails, but over the rail, so it's perfect to adapt to almost any older car. I used a junkyad Camaro column, and kept the factory joint with it, then DD to a Flaming River joint to adapt to the box splines.
 
#70 ·
I've known people who connected a GoPro camera to their suspension on the front of a straight axle car to view the movement during normal driving. It will show there is a slight deflection or side movement without a panhard bar, but it is so slight (even on a fairly high gasser) that I really think a panhard bar is not needed. If a person used a monoleaf spring setup, or a very pliant spring, then this might be an issue, but with most multi leaf spring packs I doubt you'll get enough side movement to even notice.
I've done a lot of parallel leaf straight axle builds, and never used a panhard bar. It sure wouldn't have any effect on "death wobble" with or without a panhard.
 
#68 · (Edited)
You are absolutely right...there is a lot of pressure deflection period, not just on turns... on the leaf springs. they literally handle the load, (pun intended) if you've got a "bbc", sbc, or straight 6. perhaps richard ruth's car was a better design. when i get older, i might build an axle set up like that as well, and just swap mine out.
 
#64 ·
I noticed on your setup (as well as most others) there is no panhard bar to locate the axle's side to side motion. I'm currently building a traditional '23 Track-T and the manufacturer recommends a front panhard bar with the transverse leaf. They said it isn't absolutely necessary because the axle is located to the spring perch via a pin in the top of the spring, but it greatly improves drivability. It seems to me that with the really tall leaf setups that these gassers have, they would benefit from a panhard bar...not saying his is his problem, but just a thought...
 
#65 ·
carmine's axle is not a transverse type, it's got two parallel (sp?) leafs.
on a transverse sprung axle the axle "swings" on the shackels, that is why I put a dead pearch on my Model A.
 
#62 ·
i've got mine set up exactly like the 55 trucks. the arm rotates from outside of the frame rail. front to back not side to side like a cross link. i've got mine with the shackles in the front as well. i had them originally in the rear. not much difference, but i installed longer leafs made it a little softer. are you running rubber bushings inthe leaf springs, as they come, or with some metal sleeves, or straight metal slugs, which helped mine from moving the complete axle left to right, which i believe is where some of my handling problems were originally from. i also had some shocks angled, i only have one that is angled now. i'm running three. two that are perpendicular to the frame and one that is only an absorber for the steering side.
 
#60 ·
There's a lot of good info here from some very knowledgeable guys. I've never had, and always wanted to have an axled tri5.

My only experience with them was when I was kid getting able to steer gassers back to the pits behind tow cars. At certain speeds the wheel wanted to rip itself outa my hands! I asked the older guys about that, after they laughed at me I was told what everyone here already knows about, toe-in. At the track they didn't want the extra resistance of having the tires turned in so they'd run the tires straight, which of course caused the wobble.

I also got to pump the front tires up pretty high. I learned it would decrease their times slightly, and was told it would help with the wobble too.

I was about 15-16 yrs old at the time and got to do alot of grunt work which taught me a bunch.
 
#72 ·
Hey Carmine, following your front end build threads over the past year or so has been a cool breakdown of all the ways to try to make a gasser go straight (or not). Given the number of scary ski sloping drag links etc around (including mine), it should be required reading.

Looking at these pictures, I suspect that your steering arm could twist at the spindle, which might contribute to the bolts coming loose there.
If the arm goes say 6" back from the spindle, and bends 4" up from the spindle, a good amount of the force between the pitman and steering arms will go into a twisting force above the spindle, as opposed to rotational force turning the spindle (6" back to 4" up would be 33% twisting force 66% steering force, or something like that). If the steering arm was completely rigid, it would not matter, but in this case it may not be rigid enough. With the gusset stiffening the arm at the up-bend, any twisting force would be applied between the gusset and the bend where it bolts to the spindle.
This shouldn't cause the death wobble is everything else was set right, but it might make it worse when it happens. Kind of like a torsion bar with no shock damping.
And it might put more stress where it attaches to the spindle than the arm was designed for.
If my description sounds screwy, picture the arm bent up even more, like 6" up and 2" back from the king pin pivot, 75% of the force would twist the mount at the spindle and not much leverage would rotate the spindle.
 
#57 ·
Probably just got loose from the constant back and forth motion of driving the car. I have had all sorts of bolts and nuts work loose on builds, and usually not critical parts.
I would suggest that anything critical should be assembled with Loctite Blue, even if you use lock washers, or nylock nuts. This is my preferred method, and I use Loctite in conjunction with lockwashers on all steering components that don't have castle nuts and cotter pins. I use it on anything else that works loose, before I tighten it back down, to prevent further issues.
 
#56 ·
Thank you

First, I'd like to thank everyone for their continued responses. I really do appreciate everyones time. effort and suggestions. I received many more then I thought I would. Definitely alot to think about. What a great group of folks. Thank you very much, one and all.

Re. cross steering, I originally had it this way with a 14" fabricated pitman arm to be able to connect with the center link and then to the passenger side steering arm. I did it this way because of the oil pan being in the way big time and from what I read, it would give the least amount of bump steer. Someone said it would steer like a Mack truck and they didn't lie. It also gave me a severe case of death wobble at about 40 mph. So I changed it to traditional steering. I might add that I also looked at some different configurations of oil pans, but just don't know how I could ever make them work. The motor sits forward maybe 2" which doesn't help with steering alignment.

With the traditional steering, I went with a stock pitman arm, used a tierod end to connect to the driverside steering arm which is mounted on top of the spindle. The steering arm, as did the rest of the straight axle parts, came from Speedway as a kit. Part of the steering arm was fabricated to be able to reach, height and length wise, the tierod end. The steering arm is 3/8" thick and I used 1/2" flat steel for what I needed additionally to make it work. I did the measuring but I had it professionally welded. It does have a gusset welded in. I don't believe this is flexing, but I will certainly check into it.

I was out in the garage the better part of the day, just kind of looking things over. I took off the driver side wheel to get some better pics of what I mentioned in this tread. I will post them later this evening. Not sure why, but I gave a tug on the tierod end. This was kind of loose/sloppy. At first, I thought it was maybe the Heim hardware that was allowing this. A few more tugs and I saw that the steering arm attached to the spindle was loose. OMG. I could actually slide this a bit. Here I go again, but I could have sworn that I had all this tight. I don't have a clue as to how it loosened but it did. Tightened this arm and also the bottom one which also required some attention. Went to the other side and everything was good there.

I know that the steering has some issues, but not having the simple,
basics done proper, only adds to my problems. I'm going to go over all the nuts/bolts again, change the gearbox and try to reduce the caster. A friend is using my lift, so it's back to my roots: floor jack and cardboard.

As I mentioned previously, I will post some additional pics this evening. Kindly take a look. Maybe something additional will appear. Again, many thanx, Carmine.