1965 Olds 442 Vibration

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Hello,
My father and I are restoring a 1965 442 and are trying to figure out a high speed vibration since motor rebuild. Sometimes you even hear a roaring sound from the back of the car. Here is the story the engine is the original 400ci that we bought from a swap meet. We rebuilt and balanced the engine including replacing the crank and every since we put it in the car we have the vibration. This is a fast paced vibration that starts to come in at 65mph. Here is what we replaced so far: Driveshaft, Rear end rebuild, trans rebuilt, Flexplate, All mounts (Trans & Motor). The thing that has me puzzled is the prior engine (350) was smooth as ice. Not sure where to go from here and am looking for more ideas if someone has any.
Thanks In Advance,

posted by  kdagenais

does it go away if you put it in neutral? have you had the wheels checked for balance and runout? maybe try switching the front and rear wheels. or note the rpm that it occurs at and run it up to that rpm in 2nd or first and see if it is still there to pinpoint what drivetrain component is causing it...

posted by  dodger65

We have moved the wheels around and the vibration is still coming from the body of the car not the steering wheel. This shake is definetly a drive train problem not tires. It doesn't go away if you put it in neutral at speed. haven't tried other gears yet!

posted by  kdagenais

If you put it in neutral and the engine rpms drop, the vibration stays the same? that is, is it speed related, or engine rpm related? Does it follow the same pattern in each gear?

If the vibration remains when the rpms drop when you put it in neutral at speed, then it's not engine related.

How about U joints? You say you replaced teh driveshaft? Did you replace it after you found the vibration?

And a vibration from the rear wheels will feel like it's coming from the chassis.

posted by  ChrisV

Chrisv,
The driveshaft was brand new not rebuilt. The vibration is still there if you throw it in neutral at speed. There is a little of play when you grab the drive shaft at the tail of the tranny. It is so little I can't imagine that it is the cause but possible.
Starting to wonder if the driveshaft we put on was bad. Just find it hard to believe it is because the vibration was exactly the same with the old drive shaft.

posted by  kdagenais

Did you re-use the U joints when you put in the new shaft?

the reason I have gone this route in teh diagnosis is this: when you put the trans in neutral, and the vibration stays, then it isn't related to ENGINE speed, but instead to road speed. And when it's in neutral, everything ahead of the output shaft on the trans is out of the question.

If it were engine related, it would be there at the same rpm in ANY gear, and would go away when the engine dropped to idle if it wasn't there at idle with the car stopped.

Process of elimination.

You have trans output shaft, driveshaft, U joints, rear end, and wheels/tires. I'd discount the rear end as you ddnt do anything with it (though there's often the possibility that it was something that started at the same time as the engine swap by coincidence. Stranger things have been known to happen). You say you changed the driveshaft, and the vibration was there before and after the change. I doubt you'd get the same vibration from both, so it could be something like the U joints. They CAN simply "go out." I've had a couple do that.

posted by  ChrisV

The drive shaft was complet with new U-joints also. But probably would be our luck that they where bad also. May try to change them and see what happens since they aren't very expensive.

posted by  kdagenais

you might want to check for a bent axleshaft...

posted by  dodger65

is it the original rear differential and you just slapped new bearings in it or is it something special that was put in for the resto

posted by  BanffAutoSpa_ap

Interesting you mentioned that because we did have a problem with the right rear axle sliding out on us. It only came out twice but the second time the wheel was well out beyond the wheel well.

BanffAutoSpa_ap
The rear end was rebuilt along along with new gear. All bearings where replaced at this time.

posted by  kdagenais

why did the axle slide out? is that a c-clip rear end in that?

posted by  dodger65

Was it vibrating before the axle slid out? I was under the impression you did the rear end/driveshaft/etc AFTER it had been vibrating in an effort to cure it, since you say that the previous engine was smooth. This implies that the vibration started after the engine rebuild but before the rest was done. If the rest was done at the same time, then that opens up another set of posibiliies, like that axle issue.

This points to why we need accurate information when asking about a problem, as the diagnosis process is completely different if ONLY the engine work was done vs ALL of it being done at the same time.

posted by  ChrisV

The rear end rebuild was a two fold reason. 1 go from 2.83 gear to 3.55 & 2 hope to fix the vibration. The shake started after the engine swap but we changed the engine shortly after the first time the axle slid out. I forgot all about it unitl dodger65 mentioned check for bent axle. I am pretty sure it is just coincendence that the shake started after the swap. With the shake at speed (60 +) not RPM it has to be the drive shaft back. When we had the rear end rebuilt we had them look at it and they couldn't figure it out either.
would the little slop when I grab the drive shaft at the tail of the tranny cause this? It isn't allot but not sure if that would cause the problem or not.

posted by  kdagenais

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