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HI
Background:
I have converted my 77HZ from a 253 with trimatic to a 305 with a M21 aussie 4 speed. The whole package fits and goes well.
Problem:
The problem that i amd experiencing has onlt just started to become apparent after about 3 months of driving.
The nature of the problem is that im now getting a vibration though the car. When I am cruising on the roas at 100k all is fine. When i back off a l,ittle and then sit on about 90-95 I get a vibration in the car. When I speed up the vibration then decrease/goes away. Whne the vibration comes on I have pushed the cluth in an the vibration is still there.
Does anyone have any ideas what might be causing the problem.
The wheels have had an alignment
I use the original tail shaft which fitted like a glove
I did not have the tail shaft balanced
I did noy change the uni joints as they seemed to be in good nick
Thanks
Andy
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only thing i can think of is maybe the uni angle changed on the tailshaft with the transplant and the speed youre doing coincides with a particular harmonic.
the fact pushing the clutch in doesnt make the noise go away suggests its road speed related.
If it were me, id be having a look at the unis for any increased wear and probably measure up the driveline angles too.
I lost a tailshaft at about 110mph, i tend to worry about these things now lol.
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So it's at 90 to 95 km/h i would have a good look at your tyres they may look ok but have a real good look at them it may be starting to bubble on the side wall or the tread lifting off the belt.
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Yep,Look at all the above IMO,Check gearbox mount too and how much yolk is in the box and angle,diff and axles.These things are sometimes just a coincidence.OH And steering too. Edited by user Saturday, 12 March 2011 10:57:14 PM(UTC)
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Jim in Adelaide.. |
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quote:
Originally posted by jim
how much yolk is in the box
And if there is yolk in the box you should reconsider where you are making your omelettes. It's a Joke Jim! (I was gonna throw in a pun and say "it's a Yoke Jim" but you probably would have figured I was ridiculing you...)
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bolts bottoming out, trans extension housing through crossmember, seen it many times
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Agree with Frank^^^. Or possibly out of round rear wheels or tyres (easy to check). |
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I'm with greenhj, uni alignment or maybe excessive uni wear. No harm in having the driveshaft fitted with new unis & balanced. Has the car been lowered or had an diff upgrade, commodore/9 inch etc? Is the problem more noticable with a load of fat bastards in the car? Ideally, engine crank angle & diff pinion angle need to be parallel for the uni's "stop/start" characteristic to be cancelled as the driveshaft rotates. Differing angles will tend to drone/vibrate at certain driveshaft RPM or load on/load off situations. Many guys tend to poo poo this but it is fact. Google/Wikipedia this subject to reveal all the details. Edited by user Sunday, 13 March 2011 5:01:40 AM(UTC)
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utility8
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If it has only started happening after 3 months of driving it must be a wearing part such as uni joint or wheel balance/stuffed tyre. it wont be a static problem like tail shaft angles.
Either something that was balances has bent or lost a balancing weight or it has worn out. Does it ping when you first start to drive off signalling worn uni but does not always do this.
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If worn bushes in the rear end allow the diff to rotate to a greater degree than previously experienced, this angle may actually come into play. The addition of more power, along with a manual trans, may have buggered the already worn the bushes to an extent that it allows misalignment of the pinion angle when compared to the crank angle. Although thought of as a static setting, worn components may make it dynamic. Edited by user Sunday, 13 March 2011 8:03:58 PM(UTC)
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utility8
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quote:
Originally posted by 52abel
HI
Background:
I have converted my 77HZ from a 253 with trimatic to a 305 with a M21 aussie 4 speed. The whole package fits and goes well.
Problem:
The problem that i amd experiencing has onlt just started to become apparent after about 3 months of driving.
The nature of the problem is that im now getting a vibration though the car. When I am cruising on the roas at 100k all is fine. When i back off a l,ittle and then sit on about 90-95 I get a vibration in the car. When I speed up the vibration then decrease/goes away. Whne the vibration comes on I have pushed the cluth in an the vibration is still there.
Does anyone have any ideas what might be causing the problem.
The wheels have had an alignment
I use the original tail shaft which fitted like a glove
I did not have the tail shaft balanced
I did noy change the uni joints as they seemed to be in good nick
Thanks
Andy
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Hi
Thanks for all the advice and I will certainly look at all the ideas that have been suggested.
To add a few more things
1. The diff is the original salibury 3.08 diff
2. The tyre were brand new at the time the car was put on the road
3. the vibrations are not just confined to 90/95 they occur at various speeds
4. It does not ping when i first start up
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Once again HI
I took the eay option first of checking all the bolts back from the gear box to the diff. At the diff a pair of u blot nuts had worked themselves loose. After tightening them up went for a quick run and no vibration...New uni will be ordered...thanks agin to all who gave their time and advice
thanks
andy
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yep, usually is a simple thing as such, i've seen this problem maybe a dozen times when a same is done, great theories been quoted above by all, very well researched by some, but no point trying to re-invent the wheel and confusing people with einstiens theory of relativity when its totally not needed.
30min and $25 dollar fix, rather than pinion angle and diff saddle changes due to 3deg pinion change..ummm
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