Chevrolet C60s - Front Wheel "shimmy"

[jake neville]

our marmon herrington gun tractor had this same problem when we first put it on the road. the entire front axle had been overhauled and the wheels balanced. when it got around 20mph it started shaking so violently it was dangerous and uncontrolable. we fitted castor wedges to the front which made a big difference. it now only comes in mildly when you hit a bump around 50mph.

robin mawson had similar problems with his white scout car. he played around with his for quite some time. tried a number of things and still had problems. eventually he tried ajusting the toe in more than what it said to in the book. no shimmy at all from zero to flat out.

we are planning to try the same on the marmon when we get time. this obviously increases tyre ware but for the amount we drive these old trucks waring out tyres is highly unlikely.

give it a try?

[Mike K]

Originally Posted by jake neville

we fitted castor wedges to the front which made a big difference. it now only comes in mildly when you hit a bump around 50mph.

50 mph in a M-H - YOUR KIDDING So what brand of turbo have you fitted on that flathead

[cordenj]

Thanks for advice everyone.
Now off to celebrate 70th Anniversary of the liberation of the Channel Islands (well Guernsey) for a week.

Sadly not in the Chev as planned until this wheel issue is resolved, so having to take the Jeep and one of my trailers.

I'll investigate the shimmy more on my return.

[Bob Carriere]

Based on all the work that has been done already .....

Start with the tie rod ends....... they can be disassembled to visually verify wear...... not unusual to see oval wear spots. Look at the tapered hole where the tie rod connects to the eggcup..... in some case the tapered hole has gone oval...... they can be machined larger and a new tapered insert manufactured.

Then move on the steering arms..... take them apart...again not unusual to find some round pins with significant wear spots..... then move on to tighten the steering box..... which you may need to remove and look at the innards .

If none of that improves the shimmy look at totally disassembling the front axle egg cups...... there are NO cone bearing in the CMP like the Dodge axle. You will be looking at the New Departure 928 bearings mounted on solid pins... they should be hard to remove as they are a tight fit..... any looseness or wear patterns should be visible to the naked eye...... when removing the end caps you will find small circular shims.... save them and keep track of how many which side.....when you reassemble you need to preload the bearing as per the manual. Dirk as the New Departure bearings and use to have spare shims..... other wise start buying front axles for spare parts. I have taken CMP front axles apart that the New Departure bearings where literally worn out and fell apart in my hands. Old bearing if good are usually a tight fit and and need to be pulled out and pressed back in place.

From my experience you need to start at the wheel bearings which has been addressed then move on to the next connection point one step at a time.

I know you can ruin the front axle of a Dodge M series in one Winter of driving with wheel chains..... the solution was to have the oval holes of the front axle flange drilled out and new tapered inserts pinned in place..... it would have been cheaper to buy a scrap M37 for parts. The tie rod ends were also replaced at the same time.

Good luck.

Bob C

[cordenj]

Back from the Guernsey 70th Anniversary trip (in the Jeep) and now back to trying to resolve the Chev's Wheel Shimmy.

As two heads are better than one, I asked good friend, expert mechanic and fellow CMP owner, Andy to give me a hand to investigate further.

We spent all day yesterday working through the front axle.

Started by checking and slightly tightening the steering box. A test drive showed some improvement but a dose of major shimmy meant more investigation was required.

As some have said here, we think this is a combination of different factors that cumulatively cause the issue.

So logically it is a case of going through each possible cause and trying to eliminate it ,apart from what I've already listed earlier in the thread:

1. Steering Gear - checked, adjusted and ok
2. Front Axle tie rod - checked and in good condition
3. Wheel bearings - both sides are correctly set and in good condition
4. Pivot Pin bearings:
Near-side_steering knuckle binding slightly in the the chromed housing. Checked shimming and reset to avoid binding. Both bearings in good condition.
Off-side_steering knuckle binding in the the chromed housing. We think this side was overshimmed and had placed great pressure on the Pivot Bearings....unfortunately both need to be replaced....so will be trying to contact Dirk or Stefan on Monday for replacements.
We suspect that this wheel shimmy is not a new issue on this vehicle and that the bearings had been very tightly shimmed in an attempt to stop it.

5. Front springs - The photos below show the front springs, which have clearly sagged over the last 70 years......and as several posters on this thread have suggested, this is probably the a major contributor to the shimmy issue and the caster will be way out.
Close examination of the photos show some small wedges have been fitted in the past. My plan now is to try to get a pair of larger wedges machined a at a local engineering shop.

Once new Pivot bearings hopefully sourced and are fitted and the new wedges are placed between the spring and axle....and we'll see what happens.

Can't help feeling the real solution is a replacement set of good front C60S springs which can restore the correct caster. Anybody know of any in UK, Belgium or Netherlands?

[rob love]

You could take the springs to a good spring shop for re-arcing. Springs are "bull-work" and I have always generally found having this done to be very reasonably priced. The shop will dis-assemble the complete springs, re-arc each leaf, install slip pads and rebound clips as necessary, reassemble them, and you can do the spring bushings at the same time.

Just make sure they don't over do it. We used to have empty trucks leaving the shop looking like they were carrying tons of weight becaue the front ends would sit higher than the back.

[cordenj]

Thought I'd update on the continued frustrations of the wheel shimmy.

The parts arrived from Dirk very efficiently and we fitted the pivot bearings on the side where they had been over shimmed and damaged in the past.

I made up the special tool from the "Sept 43 Service Information Bulletin", to enable me to put tension on the Pivot Pin to correctly set the bearing tension.

While this was going on I had a pair of 3 degree and 6 degree wedges made at a local engineering shop