1960s 1960 Annoying Vibration

[60eldo]

So Ive had my 1960 CDV for about 5 years now with this vibration in the steering wheel. I cant seem  to figure it out. It starts at 20 MPH - 25 mph then goes away. Comes back at 40 and smooths out at 45 mph Returns at 60 . So I dont think its the wheels, I had all 4 balanced at 3 different shops. I then took off the 2 front tires with rims and put 2 different tires and rims on, with NO difference. Just had tranny rebuilt, and put on a different drive shaft and bearing. NO difference. Is it possibly the motor mounts, the engine  is old and has 75 lbs in one cyl, maybe this could cause the vibration. Also crank bolt broke inside so I put another one in half way that is about an inch too long so I used 5 or 6 washers to make it tight. I know sounds pretty mickey mouse, but, why is it at such low speeds. Cant be the wheels. Any help wood be great.

[TJ Hopland]

You should be able to determine if its the engine by going to neutral or forcing it to another gear so its running at a different RPM for the same road speed.   If its the engine that should change things.

[60eldo]

 I should also say that while driving and she starts to vibrate at 40 mph, when I throw it into neutral or shut off the car, it continues to vibrate,. Update I just tried leting the car idle at 600 rpm and hooked up a rpm gauge, I slowly , while in neutral, revd the car to 900 and it started shaking the same way and stoped around 1100,,mmmmm, is this my problem? And whats doing it, the crankshaft bolt, motor mounts? bad cylinder

[60eldo]

So heres a pic of my crankshaft bolt on the left, other 2 are just spares to compare. As you can see parts of my bolt is still in the crank so I just put a longer bolt in with 5 or 6 washers.

[Chopper1942]

A perfect running V8 engine has a natural E4 vibration. The engine and transmission mounts are designed to eliminate this vibration from being transmitted into the frame and body.  If your mounts are original, they have deteriorated by now.  The cylinder with only 75 psi does not accelerate as fast as the other cylinders on the firing stroke. This causes a slight rpm change and causes an engine vibration different than the natural E4 vibration. This is how the ECM, using a CKP (crankshaft position sensor), monitors engine misfire.

If you want to know exactly what is causing the vibration and not just throw parts or use WAG's, go to a GM dealer and inquire the cost to have a tech use a Pico scope and GM's NVH software and an accelerometer to determine if you have a T (tire), E (engine), or P (prop shaft) vibration or maybe a combination of them.

Tires can be in perfect balance, but if there is road force variation in the tires, you can still have vibrations.

[60eldo]

 So yesterday I removed the H balancer bolt. And used the original one with one washer. I had to cut about 1/4 off so it would go all the way in, remember my original bolt ,some broke off inside the crank shaft. Could only torque to 40lbs cause the bottom pulley started to turn. Proper torque is 60-80lbs. Anyway no difference vib still there.

[Dave Shepherd]

How did this start? Any connection  with work on the balancer?

[60eldo]

 Dave I cant really remember. I think when I got the car for some reason I wanted to take off the bottom pulley and the bolt snapped in side the crankshaft. I was luckey that half the bolt came out. So I cut another one and there was enough there to get it in.  So if its not that, then Im thinking motor mounts, maybe they are so old and rubber is like cement taking vibration to body and steering wheel.

[Chris McBride]

Attached is a service summary which the Cadillac dealership might have used in 1962 to try to diagnose and address your issue.  The pictures are murky but the text is legible.

Vibration issues have bedeviled many.  I hope this helps resolving your problem.

Good luck!

[60eldo]

Thanks Chris, thats very interesting.

[Dave Shepherd]

Dave I cant really remember. I think when I got the car for some reason I wanted to take off the bottom pulley and the bolt snapped in side the crankshaft. I was luckey that half the bolt came out. So I cut another one and there was enough there to get it in.  So if its not that, then Im thinking motor mounts, maybe they are so old and rubber is like cement taking vibration to body and steering wheel.

motor and trans mounts can both cause issues. Look at them see if the look and feel like "cracked dry biscuits".

[Cadillac Jack 82]

I had a similar vibration on my 57 that ended up being a rock hard trans mount.  Replaced that when I serviced a leaking rear trans seal and boom!  gone.

[60eldo]

OK wheres the best place to get motor mounts made in the old US of A?

[Chopper1942]

RockAuto.com has engine mounts listed. Might call about trans mount.

[Cadillac Jack 82]

In case its the trans mount heres a link for one on Ebay:

https://www.ebay.com/itm/224315417262?hash=item343a3da2ae:g:YKoAAOSwLy1eLxD4&amdata=enc%3AAQAIAAAA8F%2Fgh75e7we%2BiY928QwxOFeDC3R6VE%2FFX1A0CxkS5Ai%2FIwjYB8pZUkl1SOEBjfmoSY0O%2Fs0MO9gs4ShAGzSbGOT%2FrB55X2WTuDJq2tIR1gibpvdubiGovGqCRtbxPjsm2uJnb8Kse5tx%2BErXdzRvV%2FHVpJkDZNUQK9NfpQKEE6L6WvLGE0I8R%2BDi7VVWE2mYKoDYi93YwgDtKr8cV0p%2FryOiVCZt6I5sP0pg5dVkTFUxRwIXGnRmwhPwVRNEvT2CWL0UPlOmwnNCGKi0pHBwZOoQ2ERvAYIrJG%2BCgj8PM%2BMQ%2FBAl9lJa8D16dtkYtOC3OQ%3D%3D%7Ctkp%3ABk9SR9iXp63NYg

[Steve Lomas]

You mentioned that it still vibrates when rolling in neutral or with the engine shut off?

i.e. there has to be something else besides the engine vibration

is it mainly in the steering wheel or the whole car? have you checked for any play in the steering bushings etc? drive shafts?

Other than that, I had a vibration in a 75 Eldorado I couldn't track down for years.  it would wobble at some speeds and be perfectly smooth at others,
no matter what the engine was doing and new tires made no difference.
It turned out to be the hood- the worn rubber stops were not supporting it enough either side, so it would shimmy slightly at different wind speeds.
Barely noticeable to the eye but enough weight in those hoods to shake the whole car.

[hmbmw21]

Great Info, A great topic ! Thank you.

[60eldo]

 Steve thats funny cause I thought of that too and checked it out. It wasnt the hood. This is a real mystery. I bought new mounts yesterday, when I drove car on ramps and tried to get drivers side 3/4" bolt out, I couldnt, the socet seemed to spin around the bolt, I tried and tried but no luck. Its almost like someone put a metric bolt on it. I really need a hoist to do this.

[60eldo]

Just thought of something. When I put the socket on the nut it seems to turn but nothing is happening, its not loosning. Is it possible that the bolt is spinning with the nut? That would explain that they are both turning, the bolt broke off inside the rubber. If thats true Im screwed.

[Steve Lomas]

well you thought of the hood much faster than I did

If the bolt was broken that could be a good sign;
i.e. it could be the source of the vibration you're looking for.

On the other hand, where you have a bolt exposed to rust and vibration like that, it could be the threads got smoothed off, especially with fine threads.
I'd suspect the latter as I'd think the bolt would drop out if broken? but there will be others that know this car better than I do.

Can you get a saw blade to it to cut it off?  Or a nut breaker?


Steve