Hey fellas, looking for some help with a lowered '49 F1. It has reverse eye mono-leafs and 3" drop axle. Now I am getting crazy death wobble. Everything up front is new except the steering box but it doesn't feel too loose. I noticed there is quite a steep angle now on the drag link from the pitman to steering arm. I'm guessing the wobble is most likely a geometry issue; but looking for advice. I cant move the steering box up as there is a clearance issue with the headers. Does anyone have any experience, ideas, or advice on the best way to possibly remedy this?
Pictures and more Pictures please. Bad geometry won't necessarily cause what I typically think of as a death wobble. Bad geometry will lead to bump steer and excessive tire or bushing wear. It is possible that something else is worn out (wheel bearings, king pin bushings) and the bump steer induces the death wobble when it excites the suspension. Have you rechecked the bushings? Bad geometry can cause stuff to wear out very fast. Are the tires and wheels balanced as well?
FrozenMerc has some good suggestions. The increased bump steer may be exciting the wobble. Your dropped axle may not have sufficient caster, or maybe toe-in not adjusted right?
Unless the rear was lowered an equal amount you have decreased the caster in the front end. Check the king pins for caster. If they did not add caster to the axle ends when they dropped it then you can take truck to a axle shop for large trucks, they have the equipment to twist the end of the axle to create positive caster. I would have suggested tapered shims to move the axle top to the rear but since you have mono leaf springs I am afraid they will develop a S curve from the load caused by the axle wanting to stand straight up.
New king pins, new bushings, new bearings (I might recheck the wheel bearings though), 6* caster, new wheels, new tires (tried 2 different sets thinking it could be tires), all balanced, toe-in checked and re-checked. Rear has been equally lowered
A lot of drop axles actually have a camber problem. Caster is easy to set camber not so much. I have found that a lot of steering woes on a dropped front suspension come from bad drag link geometry. death wobble can come from bump steer, especially at speed.
I have found if you use the dropped tie rod ends like Speedway sells they cause death wobble. I have had several trucks I tried to use them on. They look good but don't always work well. I found the tie rod drop blocks work better just don't look as nice. If that is not the issue sometimes to much caster can cause death wobble. Since you have 6 degree back it off to 4 degree. Wide wheels and tires also add to death wobble sometimes.
I have dropped my 56 about 6" in the front from stock.. First I pulled a few leafs.. then went to drop axle. the swap to drop axle caused tons of little issues. But after some time I got it figured out. Now I go down the road as fast as I want only slowing for big bumps. You need to heat and bend your steering arm that is attached to your spindle.. You said your steep angle on the drag link, this is the ultimate start of your issues. The drag link must be straight and pretty level. Any angle up is even worse than a small angle down. I had to ultimately bend my steering arm twice, and then put a straight drag link with heim joits on it to fix my clearance issues. Since you have so much new... I pushed mine to 10 degrees for how I like to drive on freeway. 130 and can take my hand off the wheel. Toe in needs to be 1/8" to 1/4" If your outer tie rods are worn they may deflect at speed and cause toe to change to a toe out situation then throwing you into the death wobble. I have fought this, its frustrating... But its solvable. Finally level... by stubbsrodandcustom posted Dec 13, 2012 at 1:54 PM
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