1940 Limited front end shimmy....

My Buick picks up a bad shimmy above 54mph. I have checked the front end and other than slight wear on 1 king pin it seems tight. I did have to replace a tie rod end this past spring and have checked the toe in and increased it slightly and that has not helped. The steering box has slight wear to it but not unusual in my opinion. I have read that low tire pressure could be the culprit...... not sure how. anyone have any suggestions wear to turn next? Leaving in two weeks on a tour and really need to do better than 50mph...

Have the tires & wheels rebalanced and see if that helps. I had this same problem on my 40 Limited when I first got it and the cure was rebalancing. At around 45 mph or do, the front wheel would hop up and down, bouncing along until I slowed down.

Also, go to your profile settings and under your name, proclaim yourself a Team '40 Member.

Chad, don't know what you have for tires, but I have had belts get loose and make the front end do weird things.

Ben

Chad,

I just replaced the king pin bushings in my 12 Buick because it had a severe "Death Wobble" due to severely worn bushings.

During this process, I learned that the king pin bushing clearance should be about 0.002". You mentioned "slight" wear on one king pin.

How much wear?

I can feel a slight movement in the king pin when I pull on the wheel at the top and bottom. This is a side to side motion, almost takes the wheel out of your hands. I have had in the past the bouncing due to low/no oil in the shocks but that is not the case. I also have some drive train movement due to worn out engine mounts but that is different than what I am getting now. Will double check air pressure this weekend and with the help of a friend do some more tugging and see if we can figure out the weak link.

BigDogDaddy,

cannot find how to edit my signature to include Team '40.....

Chad, I sent you a private message.

You can try the old mechanics trick of putting shims in the kingpins. This will determine the wear by the thickness of shim you can force between the king pin and the bushings. Take it for a test drive and see if the wobble is gone. feeler gage stock works well for this test.

Bob Engle

ok,

First of all, regular maintenance INCLUDES checking air pressure in tires.....

Spent some quality time on the car Saturday prepping it for this weekends trip. Aired all the tires to 40psi, added oil to all the shocks ( this is a yearly thing, but I think I drove it more this summer and it did not last the year) and took it out for a test drive. I now feel every single crack in the road and I swear I can tell if I run over an ant with it!! Hard tires do that. Shimmy 95% gone. Both King pins need replacement and will tackle that over the winter. We even worked on welding up the cracked exhaust manifold..... no real difference. We will take it off and weld it over the winter as well but while we had the welder out we welded up the rear transmission mount. It is oil soaked and was giving too much side to side movement which became real apparent at highway speeds when you took your foot off the gas. Once driving season is over I will remove it and rebuild it with polyurethane but no time right now.

My list for the winter gets longer.......

Chad,

It would be a good thing to throw 4 tie rod ends on her like I did to get rid of the "shakes" which can appear at different speeds for different folks.

Q= how much play is in the steering wheel ?

You know there are 2 adjustments in the "box". The shop manual tells just how to adjust both.

I run 36 #'s in my bias ply tyres (for Grant and Danny).

Also check the drag link for play at each end. Mine needed a turn or two and some lube, especially the front end.

Mike in Colorado

Goodonya Mike !!

Good to see you blokes occasionally get the spelling of "tyre" correct. :)

With steering, if there is slack anywhere in the system, remove it.

I don't know about over in the States, but here in Aus, I doubt there would be too many that would know how to do a decent wheel alignment on these old beasts.

I bought the gear on eBay and did it myself and will do it again once the car is finished.

If you take it somewhere for an alignment, take the workshop manual with the instructions to do it properly.

Danny

I replace one tie rod end last fall, badly worn. I find the rest are all tight ( the replacement came off my parts car! ) Steering box seems ok, I get about 1" movement on the wheel and the rest of the system is tight except the center pivot. Aired all the tires to 40psi per sidewall and while I don't like the ride as much anymore it got rid of the shimmy. I am running close to 50w in the shocks ( they have not been rebuilt and leak ). That maybe too thick when it gets colder but I heat my garage so it will usually be warm unless gone for hours or overnight. So I did some internet research for king pins. one site shows a set for all '40 Buick's EXCEPT series 80 & 90. the set specifically for 80 & 90 is about 50 bucks higher on his site. Another site advertises them for the series 80 for 70 bucks. Does anyone know the correct part number so I can get some interchange info to get the right set? And the final question, anyone have any luck welding up the exhaust manifolds? My Buick is louder than my Ford with the 7.3 diesel in it.......

Thanks for all the help so far.

Now you had changed your toe in angle and the Problem starts ? I had the same Problems and it was the worn upper shockbushings....too much endplay in the Shaftbearings. You can't check it if the car is jacked to limit ,because the arm lies straight on the upper frame Rubber.

If you have jacked the whole car then jack it under the lower controlarm also for that the controlarms are free and check the bushings of the Shocks .

Before you had changed your tie rod end it coud happen that you had too much toe in and then there is always pressure while driving to the Shaft and you don't feel the worn Bushing. Now you have a different toe in and its possible that the Bushing beginns to shim under the less pressure on it.

M2C

The front end shimmy started prior to the tie rod replacement. While the new tie rod helped it did not cure it. I have double checked the toe in and if anything I have too much. 1/4" right now. I think the biggest problem was low air pressure in the tires and low oil in the shocks......

The next step will be to rebuild the center pivot and king pins.

First off, hi guys! It's been a while! Secondly, I'd have a look at the pitman shaft bushing while having someone turn the wheel back and forth. Drag link ok? The shock proof steering system can sometimes need a tighten up. Observe the ball stud in it's cups to see if there's any excessive movement there.

Cheers

Grant

Good to see you found your way back mate !!!

Danny

Thanks Danny!

Been over your way (sort of), cruising from Brisbane up to the islands, changing jobs, setting up charities, and fund raising for people. Plus working on an old Honda C50, the Stingray, the old Fairmont and taking some rust out of a mate's 4wd. All go. Great to be back though!

Cheers

Grant