Vibration- Ideas please

Includes clutch, transmission, propeller shaft,
universal joints, differential and rear axle.

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fraze
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Vibration- Ideas please

Post by fraze »

Hoping for someone's "light bulb" moment here. I have an FC sedan and an FB ute and both have an identical driveline vibration. It is quite a strong vibration which comes in almost exactly at 100kmh on both vehicles. It is coming thru' the driveline as I can coast out of gear and the vibe doesn't change. It is not particularly apparent thru' the steering but can be felt thru' the seat and floor. So far I have had the drive shaft on both cars retubed and balanced ( and the sedan has had the balance rechecked). I can run the cars up on stands ( rear axle supported) and the wheels seem to be running true, so i don't think bent wheels or axles.Have new axle bearings. Wheels have been checked for balance several times. The tyres are new - 185/13 Maxxis on both cars with standard steel rims. I have swapped wheels front to back and across both cars but no difference. Suspension is good on both cars with new rubbers, shackles etc. Ride height is standard, so drive line angles should be ok. Rear seat passengers make no difference on the FC. I have even tried swapping brake drums front to rear for no difference. By the way both cars have 3.55 diff ratios with the later unis, which are new. What the hell am I missing????? hope someone can help, Fraze
gpi
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Re: Vibration- Ideas please

Post by gpi »

are you getting excitations too? :ninja22:

have you checked mechanical to body mounts? :idea:
Blacky
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Re: Vibration- Ideas please

Post by Blacky »

Does it vibrate from 100 and beyond or does it go away once you reach say 110 ??
When you're faced with an unpleasant task that you really don't want to do, sometimes you just have to dig deep down inside and somehow find the patience to wait for someone else to do it for you.


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Harv
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Re: Vibration- Ideas please

Post by Harv »

When you did the driveshafts, did you put new bearings in the unis?

Cheers,
Harv
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Errol62
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Re: Vibration- Ideas please

Post by Errol62 »

Hi Fraze,
This is not uncommon in my experience with early Holden’s at this speed. How about the gearbox yolk and bush in these cars, or did you mention it already? It does seem to happen specifically at just over 60mph, independent of final drive ratio, which discounts this source.
Cheers,
Clay


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EK283
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Re: Vibration- Ideas please

Post by EK283 »

Not sure how holden set them up but I would check the drive line angles for the vibration.

My current Nissan Patrol had a vibration the same around 80 kph after i put a 2 inch lift in it.

The remedy was to reset the pinion angles, the vibration has gone.

Regards Greg
So many cars so little time!
fraze
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Re: Vibration- Ideas please

Post by fraze »

Thanks for the input guys, to answer the queries....
GPI- Mechanical to body mounts are all good, new rubbers all thru on both cars. The FC sedan is an original, unrestored and un molested car so nothing has changed from factory.
Blacky- i haven't pushed either car over 100 kmh so I will have to see if I can drive thru the vibration.
Harv- New uni joints fitted at both ends of the tailshaft on both cars.
Clay-Gearbox yolk and bush seem ok, I cant find any slack. The FC gearbox is original as far as I can tell, not molested. The FB ute gearbox was fully reconditioned less than 1000miles ago. Not ruling that out, just don't know how to check. I have swapped tailshafts between cars and nothing changes.
Greg- Drive line angles is a good question - I don't know how to check them! As i said in the original post the cars are both stock standard so drive line angles should be as factory. I have run the FC with rear seat passengers and a load of luggage in the boot, which would surely change drive line angles and the vibration is unchanged.

So - how do i check drive line angles?
fraze
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Re: Vibration- Ideas please

Post by fraze »

Thanks for the input guys, to answer the queries....
GPI- Mechanical to body mounts are all good, new rubbers all thru on both cars. The FC sedan is an original, unrestored and un molested car so nothing has changed from factory.
Blacky- i haven't pushed either car over 100 kmh so I will have to see if I can drive thru the vibration.
Harv- New uni joints fitted at both ends of the tailshaft on both cars.
Clay-Gearbox yolk and bush seem ok, I cant find any slack. The FC gearbox is original as far as I can tell, not molested. The FB ute gearbox was fully reconditioned less than 1000miles ago. Not ruling that out, just don't know how to check. I have swapped tailshafts between cars and nothing changes.
Greg- Drive line angles is a good question - I don't know how to check them! As i said in the original post the cars are both stock standard so drive line angles should be as factory. I have run the FC with rear seat passengers and a load of luggage in the boot, which would surely change drive line angles and the vibration is unchanged.

So - how do i check drive line angles?
EK283
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Re: Vibration- Ideas please

Post by EK283 »

This video explains it the best,

https://www.youtube.com/watch?v=Idk3BVDVHq4

Check your unis for phasing as well.

Sometimes the pros can get it wrong , I had a shaft made to suit 7000rpm and the pro goes it will never spin that fast, I said 1 to 1 ratio out of the gear box with the engine doing 7000 rpm is 7000 rpm. The pro goes what about the diff ratio it will slow it down, I just looked and though oh dear this genius is going to make my prop shaft !!!!!

Anyway you have to check the lot to find the vibration.

Greg
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Errol62
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Re: Vibration- Ideas please

Post by Errol62 »

Fraze,
Easy way to check using a small inclinometer. Inclinometer app on smartphone is not a bad way to go, but otherwise you can use an engineers protractor with spirit level included.

Under the car the gearbox output flange and diff input flange should be at the same inclination, parallel, give or take 3 degrees I think. Usually the diff is pointed down slightly so that the alignment improves when load increases and when rear wheel torque causes the housing to rotate on hard acceleration.


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fraze
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Re: Vibration- Ideas please

Post by fraze »

Ok so now I have watched a couple of youtube videos on drive shaft angles and phasing. I set the FB ute up on stands and got it as level as I could, visually. Then using my iphone as an inclinometer I got the following readings.
1. Phasing - spot on, 0 deg both ends across both sides of the yokes. This tailshaft was retubed only 2 weeks ago.
2. Angles. I checked across several different planes for the diff pinion shaft and the gearbox output shaft (housing). my (crude) measuring came up consistently at gearbox output shaft angle -4 deg. Diff pinion shaft 0 deg, tailshaft angle -4 deg. this puts the gearbox shaft and tailshaft in line and that checks out visually as well. So we have a variation of 4 deg across the driveline and that seems to be in spec according to the videos I watched.
I will now check out the FC sedan but visually it looks to be pretty much the same as the ute. Fraze
FbSTDwagon
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Re: Vibration- Ideas please

Post by FbSTDwagon »

Ok I’m going out on a wing saying this but your brake drums were balanced from factory, it’s a process that is not done anymore due to improved manufacturing techniques.

I spoke to PBR in Adelaide recently on this topic and they said they haven’t seen it done in decades.

Maybe you could sandblast your drums of any rust and see if the vibration is gone.

Also check your king pins for play.
Drew
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Re: Vibration- Ideas please

Post by EK283 »

At least its checked and you can take that out of the equation.

Real silly question but have you tried different roads at that speed ?

Other than that there's not much left to check.

Its frustrating I know.

Greg
So many cars so little time!
fraze
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Re: Vibration- Ideas please

Post by fraze »

I have been doing some more reading on the subject and it seems that having the gearbox output shaft and the tailshaft at the same angle could pose a problem with vibes However using the Hardy Spicer guidelines my 4 deg angle is "safe" up to 3500rpm. With my 3.55 diff ratio apparently at 60mph my tailshaft is rotating at 3000rpm. I will do my FC sedan in the next few days and see if it is the same as the FB ute. Might be something there.
Drew - I did think of brake drum balance at one stage and swapped brake drums front to rear but it made no difference. also there is no vibration in the steering so i tend to discount that.
Greg - the vibes are more apparent on good surfaces than on rough surfaces but they are always there.
Keep the ideas coming! Cheers, Fraze
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Errol62
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Re: Vibration- Ideas please

Post by Errol62 »

You could try varying the angle of the engine and box closer to that of the diff, by loosening all the fastners on the rear gearbox mounts, jacking up at the rear to take out any play, and retighten. Easy enough to do.

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