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Sudden violent vibration
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I recently purchased a 36 ford roadster , original drivetrain . It had driven pretty smooth up to this point . I was on a drive last night and suddenly the car began to shake violently, I was having to really hold onto the steering wheel it was so bad . I limped the car over and called AAA and had it towed to my house . Any ideas on what might be the culprit or how I might better figure out ? Should I try and pinpoint when the vibration starts ? Or if it still vibrates if I put clutch in ?
Any tips or insight is appreciated |
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From your description it sounds like wheel tramp. Some folks call it the death wobble.
Radial tires? They will exaggerate this condition especially with worn front chassis pieces. Me? And again, from what you describe, I'd check the front chassis VERY carefully for worn parts. Tie rod ends, spindle pins, spring, shocks and finally, PROPER alignment. It appears the car sits very low, much lower than stock. Many guys, without the necessary knowledge, simply lower the car without realizing the geometry changes along with the height. |
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The only way, that I am aware of, to get out of the vibration is to bring the car to a stop. Then when you start again the vibration will be gone until you hit the next pothole or railroad track that will start it all over again. It can be a pretty random occurrence, but not one you ever want to repeat. Good luck with your investigation let us know what you find.
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I had this happen to my modern pickup last summer. It went to driving perfectly to like driving on railroad tracks. After chasing a lot of "what ifs" and spending considerable money, it turned out to a tire that was disintegrating from the inside. The tire was only 5 years old. Needless to say I replaced all of them.
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That is usually caused by play in the front steering or suspension. With a little movement allow it allows a vibration that grows and quickly becomes violent. It usually takes a combination of things for that to happen. Possibly loose parts, bad shocks and tires out of balance. It's hard to believe a vehicle can go from being perfectly smooth to that violent from one bump in the road.
With the tries on the ground, have somebody turn the steering wheel from side to side and look for play in the tie-rod, draglink, steering box, spring perches. front spring U-bolt clamps, kingpins. loose wheel bearings, broken spring leaves broekn fron cross member.... Then jack up the frontend and spin the tires to see if there are any bulges in the sidewalls or tread (separation) or if they are badly out of round. Bias ply tires get flat spots from sitting too long and you have to drive them miles to get them round and running smooth again. Most tires will have be slightly out of round but it should not be easily noticeable. They might also be out of balance. If you do not see any weights on them, check the front and back of the rim. I would definitely have them balanced. Weak shocks can also contribute to "speed wobble". They allow the movement to get larger and larger. At the phone company we had F-350 aerial boom trucks that were loaded to the maximum gvw, a lot of weight on the rear axle. If everything was not perfect in the frontend, they would go into violent speed wobbles. When the drivers complained, I would test drive them at about 50 mph across some nearby railroad tracks, if I went across them at just the right angle, I'd better be holding on, it was liking a bucking bull. No stopping the shaking without coming to a complete stop. It's literally yanking the steering wheel out of your hands because of those heavy front tires, it continues as you slow down until you finally come to a complete stop. Then it is fine again, maybe fine for months. Usually that was from loose bushings in the front panard bar, from the frame to the straight axle. This would allow the axle with the parallel front springs to move from side-to-side, it did not take much play in those busking. Every service we checked them. We stocked a panard bar so we could quickly replace it during the service and then later we could press in and out the bushings and have it ready for the next truck. Some of those trucks, the only way to stop the speed wobble were with new panard bushings, the addition of a steering stabilizer, take any play out of the steering box, set the toe-in, new front shocks and new front tires. Because the rear weight could very on those trucks daily the caster was constantly changing which also might have contributed to it. Everything had to be absolutely perfect. As soon as the front tires got the least little uneven wear pattern the speed wobble would start again. We would mount new tires and balance them and save the slightly worn ones to run on the rear on something else. A couple years later the F-350's started coming with factory steering stabilizers so we knew Ford was having problems with them. That didn't stop the problem either. Then a couple years ago I went out and bought one of these 1994 F-350 aerial trucks with brake problems, (no brakes at all) for $2300.00 so I can trim my trees, roof the house and paint the second story and not fall off a ladder. I don't plan to be going over 50 mph in the yard so I'm not worried about speed wobbles. I looked under it the panard bar bushings are shot. |
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I think you might want consider raising the ride height a bit as well. Depending on how it is lowered (6" drop shackles?), there mght be some intrinsic problems.
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Did this happen when you were turning a corner? The front tires look like they could catch the edge of the fender.
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https://carrillocustoms.com/products...r-opening-edge
I believe this ^^ kit is what the previous owner used to lower the front |
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Check also the steering box as mentioned for play when wheels are facing front.If it has the orig steering box you might consider replacing it with a '37-40 unit. I have had a '35 and 36 a few yrs back and lowered both of them ,replaced the steering boxes and had NO "death wobble" of course all tie rods ends were tight and kingpins were new.I ran both bias ply and radial tires also.I also used most of the parts you have pictured and did not split the wishbone.
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Duplicate post.
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IMO,the tires are to big.Here is a pic of the 35 sedan I had.Dropped axle and 16" 4.5 wide Kelseys in front with WW radials.Its now in Sweden.
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This problem has been discussed many, many times on this forum.
On a stock unmodified Early V8 Check everything ! Start with tire pressure. Have all the wheels spin balanced. Look for bent rims, warped, damaged, deteriorating tires. Don't forget the lug nut holes. Then do a super critical inspection of the rest of the front suspension. Pay close attention to toe in/toe out and Caster. Look for bent, worn, incorrect/missing parts. On modified cars / Hot Rods All of the above applies. The critical issue with cars with big rear tires and small front tires is the caster. On my 32 Brookville roadster the issue was the caster. I have previously posted about the death wobble happening on this car. Basically, it was a fresh build (20 yrs ago) everything was new or 100% rebuilt including the 32 steering box. The best parts available. No Expense Spared. With the big and little tires the caster had changed causing the wobble to occur. There is a spacer that is available that mounts above/between the stock wishbone and the center crossmember. This drops the ball down and corrects the caster and stops the wobble. Please use the SEARCH Function on this site to read the monumental amount of discussion concerning the death wobble. |
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Also gonna try and figure out easiest way I can raise the front /back a little bit . I will double check , I think right now it has 6.00x 16 on front and rear for tire size |
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I tried to take a side pic of my front tire . Maybe I can bring it up a little bit in front and rear . Is there an easy way to do that or am I gonna have to buy a lot of new parts to make it happen? Im not familiar with with raising ride height |
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