EVERYTHING in the front end is new. What's more I have installed the tubular upper control arms and front strut braces. The car handles very well. the problem is, when I hit a substantial hole with the right front wheel, it will go into a fairly short lived, but quite noticeable harmonic occilation,(shimmy) that lasts a second or two. For just a moment, it feels like a car with everything in the front end worn out. The shocks are the oldest parts, but they exibit no obvious defect. When you bounce up and down on the car, it quickly damps the movement. What could be causing this? I have checked, and rechecked everything. I posted once before questions about idler arm. It is new as well, but it is not as beefy as the OEM unit. It is a Dana part. The difference is that the head of the idler arm is not as deep as the bracket that it mounts in. Instead, there is a tube pressed into the arm that does fill the space, but that could not be as solid as one where the head filled the space.

Any notions out there about what else could be causing this brief shimmy? What normally causes a front end to shimmy? My uncle in Kansas had an old farm tractor that shimmied to beat the band, but it never went over about 20 MPH. Could it be tires? They do not feel out of balance. When rolling down the highway, they seem to be pretty smooth. I think the lower ball joints may have as much as 20K miles on them. Everything else has less than 5K miles. The lower ball joints seem tight though. How can I check them out. Now that I have written this huge post, I am beginning to suspect that maybe the lower right ball joint has failed early. Thanks for any help.

Did you install stiffer torsion bars or lower the car any?

By shimmy, do you mean the car wanders a little when you drive over a bump? I just re-read...you said it was only on one side. Have you checked the wheel bearing on that side?

I'm just asking questions to get a better picture of the situation.

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'68 Dodge Dart 4dr Sedan

I did check the wheel bearings on that side. It feels like there is serious play in some key suspension part, that only shows up when the wheel leaves the ground, but I cannot see it. I checked the upper ball joint, the shock mount bolts, the alignment cams, the front sway bolts, the sway bar mounts, the tie rod ends, the idler arm, the K member mount bolts, etc. etc. I did put in heavier torsion bars, and new rubber LCA busings. The new UCAs had new bushings installed by the manufacturer. I'm still thinking lower ball joint. What is the check for play in that. When you jack up the car until the UCA hits the stop, then the ball joint would be extended to the limit of its play, or wear. Maybe prying up and down on it at that point? What are the tolerances here? I had an old AMC Hornet years ago that got so worn the balls joints almost fell apart, and I never felt anything like this.

I'll have to listen for this when we meet on Monday. Remind me.

You have a 'glass front end on this car so it will be less stiff than a stock A-body in the front. I assume your upper X-member for the T5 is beefy? I didn't look at it, but I should. Do you have subframe connectors? I wonder if it could be the chassis/body of the car shimmying and not the suspension/steering.

Lou

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Home of Slant6-powered fun machines since 1988

This post has info on checking the front end;
http://www.slantsix.org/forum/viewtopic.php?t=9231
Personally, I'd blame the shocks. The bounce test doesn't always reveal bad shocks; don't let it fool you. New, tight bushings won't bounce much.
Remember the Slinky? Stretch it out and watch the wave go back and forth? These oscillations occur in any spring when it is struck. It's the shock's job to dampen this energy as well as control large ride motions.
Torsion bars are more resistant to this problem than coils are, but not immune.
My Dakota had this problem when I bought it; new shocks tightened it right up.

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O==\=/==O

"A mechanic is Somebody."
- Jim Preston

Good point on the shox. I rode around with worn out rear shocks on my '68 Dart for several months recently before I replaced them. Bounce test was fine. Damn harsh ride and bounces on the road. Put a new pair of KYBs on, and it's back to smooth and tight (don't go there...).

What shocks do you have on there, Vader? How old? With heavier T-bars (0.890s?), you will want better shocks than most cheapies. The KYB's work well and are cheap.

Lou

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Home of Slant6-powered fun machines since 1988

I asked about the torsion bars, because I have experienced the same thing since going to .920" torsion bars on my Dart. The problem has gone away a little after the t-bars "settled" and a realignment, but the suspension still does not feel as tight as I'd like and I've experienced what I was thinking could be bump steer. BUT, recently I have come to the conclusion that the shocks probably aren't doing their job. The shocks I have on the car right now are almost 3 years old Pep Boy's Gabriel gas shocks (30,000 miles on them?).

I think I will try new shocks and see how it goes. Has anybody tried Edelbrock IAS shocks? Maybe I'll also try the KYBs.

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'68 Dodge Dart 4dr Sedan

Yep, ditch those shocks. KYBs will work with those TBs. Don't think they make IAS for A-bodys. QA-1s are supposed to be very good, but pricey. I've also heard some 80s Ford Bronco shocks bolt up and can be had in HP versions.

How is that steering box working out? How many turns does it actually have lock-lock? I see 16:1 and 19:1 listed as the ratio, but it seems like it must be 19:1 or 20:1 based on the lock-lock of 4.75 that they list.

Thanks,

Lou

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Home of Slant6-powered fun machines since 1988

Summit lists IAS shocks for A bodies, they are $70 each.

Lou,

The steering box is working out well, but to other drivers it no longer looks like I'm steering a pirate ship--that's the down side. I think the lock-to-lock is more like 4.25 on it. Steering effort isn't increased all that much, either (unless turning the car when it's not in motion...I never do that).

Here are the part numbers on the IAS shocks: http://www.edelbrock.com/automotive/ias ... dodge.html

I just ordered a set from shockwarehouse.com. They're made in good ol' USA, so I'll be the guinea pig for them and let you all know how it goes.

Pat

Thanks for all the tips. I will opt for new shocks at this point. It has been awhile on those, plus the natural harmonic frequency of the sprung weight is now different with the new torsion bars. The old shocks are Monroe gas of undetermined age. Lou, the rear disk set came, but they forgot the proportioning valve, so I will not have them on for our get together, unless I can find one at a local speed shop.

Man! I would love to drop by on monday with the Valiant to spend a day messing with you guys! Might I suggest 12 hours of tech followed by ales?
EFI, 5 speeds, big valves, rear discs....I have questions.

I could bring my spare Wilwood prop valve for the DeSoto.....

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Sandy, that sounds like fun. You have been a real creative force in the coming together of this car. Nearly everything in it, you thought of first, and sparked my imagination with your postings here on .org. Thanks. I hope we meet some day.

Fun times at Vader's place last night. Tuning the turbo Slant and BSing. Had to forego beers so I could drive back to NC though...

Patrick, thanks for shock and steering box info. I may have to try those IAS shocks...

Lou

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Home of Slant6-powered fun machines since 1988

Ahhhh BSing.
Sign at local chainsaw shop: "Im somewhat of a BSer myself, but its nice to meet an expert...please continue"

Seriously though....I consider it my missed tech event of the year.

So....how is it running now? How hard to get "close"? Will it make the big number?

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Yeah....Im the one who destroyed this rare, vintage automobile.....