These statements can't both be true.Driving revealed a vibration so original pitted drive shaft was installed and the vibration seemed to go away.
It remained unchanged with 2 different drive shafts
Explain to us how you set your pinion angle.Ttype6
Let me go back a few posts The problem really became noticeable when we changed from a 7.5 rear end with a 3.42 To an 8.5 from a Grand National with a 3.90 gear set , everything was new except the housing, carrier,Rear yoke and axles,The drive shaft from the donor car was rusted badly so a new Strange heavy duty unit was ordered with 1350 spicer grease less ujoints the rear is a conversion ujoint.
After the swap there was a very noticeable vibration starting around 50-55 mph at which time tires were road force balanced Brake drums were checked axles were checked. Finally the stock drive shaft was installed and the vibration seemed to go away. only difference between the old drive shaft and the new was the new had noticeably more play at the transmission. A spare output was chucked in my lathe and both drive shafts were checked for runout the new strange unit bottomed out my indicator, the old stock had I don't remember exactly but it was less than .030 Strange was notified and they sent a different yoke. All was well until she started running up and down the expressway at which time she said Hey my car still vibrates just doesn't start till 65-70- now.
So were back at it. And this time around it makes no difference what drive shaft,new or old changed ring n pinions and all bearings, does it without tires without drums. I haven't had the car here to try some of the Ideas that have been brought up as the Daughters been on vacation and she lives a ways away.
In short both statements are true! At this time.
A member of another forum is loaning me the tool to change the rear bushing.
Also Phil's transmission in Clio,Mi has the tool and for what I thought a reasonable price will do it if the other falls through
Thanks
Mike
Based on what you have written here,your pinion angle is 1 degree down. There's nothing wrong with that and in fact I wouldn't change it because when you accelerate,your pinion will rotate upward. If you have stock control arm bushings,the pinion will probably move to zero pinion angle and continue past that to an upward pinion angle. It's not enough to cause a noticeable vibration. There is no need to ever look at u-joint angles. You only need to know the angle of the output shaft of the transmission which is the same as the crankshaft and the angle of the pinion.Hi All
First of all I'd like to thank everyone for the ideas. I'll try and respond in order.
Evil
I've tried to be careful not to claim that it started with the rear end change it very well could be that the difference in drive shaft speed between a 3.42 and a 3.90 or 4.10 brought the speed at which the vibration occurs down enough to be more apparent.
Pronto
A 4 wheel alignment was done and all that was off was the thrust angle which showed up as rear toe +.4 on the left -.37 on the right Camber was -.3 on the left -,1 on the right, adjustable rear control arms were used to correct both the thrust and pinion angle.
Ttype 6
Both the motor and transmission were updated a few years before at the time headers were added, when we went to hook up the column linkage for the prndl indicator the headers interfered so the lower trans mount was lowered 1/2"
Angles were measured two different ways first a digital angle finder was used to measure the angle at the harmonic balancer this angle was 3.5 deg down from front to back, drive shaft was measured the same way at 2 deg front to back,pinon was measured by removing the drive shaft and reading off the yoke face measured front to back at 2.5 deg down. For a front ujoint angle of 1.5 and a rear of .5 which is a difference of 1 deg right at the supposed limit.
second method was a kent moore tool that just compared ujoint angles but the cross member had to be removed for this gage to fit,every attempt was made to put the transmission where it would sit if the cross member was installed this gage doesn't give true values rather is used to calculate ujoint angle both methods gave the same results. all measurements taken with full weight on the suspension as close to level ground as possible.
Thanks Mike
We're saying the same thing I thinkbut the two angles should mirror each other for vibration free operation. ( one is +1 other is -1 ) they cancel out each others oscillation.
Yea I'm thinking I don't agree with that statement.
My understanding is that they should be parallel to each other.
one example being http://www.4xshaft.com/driveline101.asp
on a drag car it is practice to run the pinion down a little so under power it rotates up
But lately I've wrong a lot.
Thanks Mike
You are correct.but the two angles should mirror each other for vibration free operation. ( one is +1 other is -1 ) they cancel out each others oscillation.
Yea I'm thinking I don't agree with that statement.
My understanding is that they should be parallel to each other.
one example being http://www.4xshaft.com/driveline101.asp
on a drag car it is practice to run the pinion down a little so under power it rotates up
But lately I've wrong a lot.
Thanks Mike
You are saying the same thing. As long as the two shaftsbut the two angles should mirror each other for vibration free operation. ( one is +1 other is -1 ) they cancel out each others oscillation.
We're saying the same thing I think
Did you look at the pic I posted in link?
Mirror is exactly the right word.Looking back on it, Pun intended, i can see that mirror was the wrong word. But we're all on the same page.