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Posted: Tue Mar 10, 15 6:50 pm
by drewcrane
[quote="GJUK"]How can the prop angle make such a huge change?
(serious question)[/quote
The angle counter acts the other angle, acting as a cancellation, resulting in no vibration,if they are even with each other as they spin faster a harmonic will develop resulting in a vibration at certain speeds,now this is the laymen s explanation and I understand it
,but I too messed with the angle I even bought some angle wedges designed for lifted trucks I have that thing tilted 3 degrees and I couldn't even make it down the street, I did find most of my vibration it was the wilwood rear brakes the hub was just slightly to big ,and even with it vibes like an earth quake. and I also had an aluminum drive shaft made,and that helped a bit I went though u joints, cut the old drive shaft to see in side and there was a pretty decent dent in on the inside damper, so it was alot of little things including tires,I had them balanced and drove on them for 500 miles and had them check again and sure enough they were out of balance again
The car still has a slight vibration ,in the seat but I just gave up and at least I can see out the rear view mirror
Posted: Tue Mar 10, 15 9:00 pm
by GJUK
Interesting.
So for example if your gearbox was pointing to the ground by 2 degrees, the prop would have to meet the diff, which was pointing up by 2 degrees?
Posted: Tue Mar 10, 15 11:37 pm
by drewcrane
GJUK wrote:Interesting.
So for example if your gearbox was pointing to the ground by 2 degrees, the prop would have to meet the diff, which was pointing up by 2 degrees?
Yea or the other way around, as long as there is the same angle present.
Again I am no expert,as a matter of fact that is how I met Dave R he had his forum and my bro Buzz found it and from then on I have tried alot of different things I have found on boards.
My car I am convinced my vibration is a body vibration,
two parts of steel slapping each other ,mostly in the floor,I cant do anything else off the car I even used a frame alignment tool and found the right front was higher than the rest of the car,
due to the previous owner going jethro and launching it off a curb.
These cars are old and have been through alot, and who knows what some did back in the 70,s
Posted: Wed Mar 11, 15 8:42 am
by db
I found this helpful, especially as mine's non-standard (4-link)
I also found a digital magnetic spirit level was superb for jobs like this.
Ignore the circles- they're for my set-up!
Posted: Wed Mar 11, 15 10:49 am
by Dave-R
UJs work best at a slight angle.
Every rotation makes each UJ on the driveshaft rotate at the same speed.
The greater the angle in a UJ the further it has to swing in each rotation. So the faster it has to swing.
When they are at the same angle at each end of the driveshaft they are swinging at the same speed as each other. They are at the same frequency but out of phase by 180 degrees. So the frequencies they produce cancel each other out.
If one UJ is at a different angle to the other they have different frequencies.
When two different frequencies travel together you get some bits that are cancelled out as before but also other bits where the amplitude (height of the wave) is added together.
So now you have these spikes of vibration moving along the driveshaft with rpm.
Hope that is understandable.
Posted: Wed Mar 11, 15 11:21 am
by GJUK
Should be a Sticky! Very interesting thank you.
Posted: Wed Mar 11, 15 11:26 am
by Dave-R
Actually I just made that up.
But there is a chance it is right.
Posted: Wed Mar 11, 15 12:31 pm
by MilesnMiles
Posted: Wed Mar 11, 15 1:01 pm
by Dave-R
Good link!
Posted: Wed Mar 11, 15 1:31 pm
by db
Great info Miles
Posted: Wed Mar 11, 15 2:37 pm
by MilesnMiles
Yes, I was most impressed as I have some vibe issues to address too.
Posted: Wed Mar 11, 15 4:59 pm
by drewcrane
Very nice Book marked
Posted: Tue Apr 14, 15 6:12 pm
by sinny
Much to my frustration the vibration saga continues!!!
I've replaced the trans bush & adjusted the angles so the trans is pointing up 2.5 degrees & the diff down 2.5 degrees but no joy!
Today I pulled the half shafts out & ran it on jack stands & the vibration was still there! But it's not the with the drive shaft removed. I've changed the driveshaft for a 2nd hand one but no joy.
My thoughts are now that both propshafts I've tried are out of balance but is there anything else anyone can think of?
Posted: Tue Apr 14, 15 6:36 pm
by Pete
I take it you changed the Pig for a different ratio one as well?
If you had pulled the half shafts and it still vibes it's not likely to be the half shafts unless I have misunderstood your post....
Posted: Tue Apr 14, 15 6:58 pm
by sinny
Hi Pete,
Yes changed the pig for a 3.23 & you understood the post I should have said propshaft out of balance!