A-body adjustable control arms and pinion angle vibration issues pleae help

[rockytopper]

I have been reading up on drive line angles. Here is one thread https://www.pro-touring.com/forum/showthread.php?t=54656 (https://www.pro-touring.com/forum/showthread.php?t=54656) Let me give some back ground on were I'm at. I have a 1965 cutlass that I have installed an ls1 4l60E trans. The rear end is at stock height the front is lowered about 1.5 inches. I drove the car approximately 9200 miles before I decided to do a high speed test run. I lost the drive shaft at 130 mph. I found part of it, it was twisted into about 12 inches from the front yoke. It also damaged the yoke on the rear end. I had the driveline shop build me a bigger 4 inch diameter shaft. The drive line shop tour down the rear end and checked for damage. They said all they had found was that the original yoke had back out and loosened but the pinion and ring were not damaged. They replaced the pinion bearings, yoke, and put a new seal in the rear. I got the car back and I now have vibrations that were not present before. The vibrations start lightly around 60 mph. They are not to the point were you think things are going to come apart but it is noticeable and the mirror is just a blur above 60 mph. At 70 mph you think the car is going to shake it self apart. This was present in this car before the driveshaft came apart but not as extreme as it is now. In fact this car had a vibration in it at 70 mph ever sense I have owned it even with the factory drive train. You can go above 70 and it smoothes out again but not like before. Another thing is it vibrates when you let out of the throttle and coast it did not do this before the incident only on the 70 mph mark.
I'm posting this in an effort to determine what is causing this. Did the larger diameter drive line magnify what had already been there? Any how I know my drive line angles are way off and I'd like to address that as a starting point. The engine and trans are set in the car at about a 5 or 6 deg angle down. The drive shaft is in at about 3 degrees down and the pinion is about inline with the drive shaft. So in my case it looks like I will be adjusting the pinion down to achieve equal working angles like this \ _ /. Another words not \ _ \ which in theory is best and is equal but opposite angles. I will have equal angles instead which i have read is also ok. My question is I want to buy adjustable control arms. Some suppliers have fixed lowers and adjustable uppers and others offer adjustable uppers and lowers. How should I go about this? Is there any pro's or con's on adjusting the pinion angle using only the upper vers upper and lower adjustable. It appears I will need to rotate the rear end about 1.5 to 2 degrees to get equal working angles. Is this doable without impacting shock and spring perches?
Thanks in advance
Rocky

[The WidowMaker]

can you check the balance on the ds? since its the only new part and the problem has amplified, i would at least take the time to get it tested before you waste any more time.

as far as the angles, do whatever is necessary to bring the w/a's down. if you have to go \ _ /, do it, but be prepared for the nay sayers.

Tim

[rockytopper]

Thanks widow maker, I'm not concerned about the nay sayers my butt will be the judge. There are other industrial drive lines that \_/ is common place. I agree I'm going to pull the shaft out and have my better half pull me up to 70 mph and see if I can isolate the problem or elimate the drive line as an issue.

[rockytopper]

I'll make this easier simple question. Some suppliers have fixed lowers and adjustable uppers and others offer adjustable uppers and lowers. How should I go about this? Is there any pro's or con's on adjusting the pinion angle using only the upper vers upper and lower adjustable.

[gearheads78]

Have you thoughly checked the transmission for damage. I have seen many driveshafts come out at high speed crack the transmission case somewhere. Look close around the belhousing for cracks. At stock height rear you should not have much driveline angle issue. Its when you go low on an Abody you start having problems. Don't even think about \ _ / in any thing other than a very slow turning industrial appication.

My car being pretty low took a 1/2" spacer under the trans mount to get right.

This the the best thread I have seen on the subject. I followed the advice and the link and it turned out well.
https://www.pro-touring.com/forum/showthread.php?t=40904&page=10

[rockytopper]

Richard I'll look into that. But the drive line angles are off because I installed the ls1 4l60 e at a 5 or 6 degree down angle. Partly because the trans tunnel is tight against the 4l60e and also the oil pan barely clears the steering knuckles as it sits. I'm not sure how much I can lift the back of the trans without causing other problems. There fore I cannot have \_\ this because raising the pinion angle is only going to increase the working angle of the trans end above 3 degrees which is also not good. I have read alot of info on this but I can't understand when I look for example at my new stock chevy truck it does not have equal drive line angles. It looks almost identical to what my car looks like. A very distinctive working angle at the trans and almost directly in line with the pinion. What gives with that.

[rockytopper]

I found this site that states that the \_/ is less desirable because of suspenion travel but it does not state that it is a absolute no no. http://www.drivetrain.com/parts_catalog/drivetrain/driveline_angles_and_phasing_problems.html. I'm not trying to buck the system but I do not believe I can achieve \_\ without major rework of my tunnel which is not an option fo me.

[The WidowMaker]

again, \ _ / is not an issue for high performance cars. all you need is working angles within 1* of each other. the harmonics will cancel each other out. the angle has no idea if its opposite or the same or whatever.

im not a driveline engineer, but i made sure to speak with a few before i set my car up this way.

Tim

[gearheads78]

again, \ _ / is not an issue for high performance cars. all you need is working angles within 1* of each other. the harmonics will cancel each other out. the angle has no idea if its opposite or the same or whatever.

im not a driveline engineer, but i made sure to speak with a few before i set my car up this way.

Tim

I would like to see more opinions on this. Everything I have read or been told is that is a huge no no in a high driveshaft speed application.

[The WidowMaker]

like i said, im no expert, but what ive read and been told leads me to believe that its a perfectly acceptable setup. the main reason for my use was the fact that the pinion sits higher than the rear of the tranny. this means that pointing it up would increase the w/a's. although they would be acceptable, my current setup provides for 1* front and rear angles.

here is a website for reference;

http://www.vibratesoftware.com

it uses the front of the vehicle as a reference pt, and if the item points up towards the front of the vehicle, its considered an up angle (you can think of it however you want, but for this site you must use the previous).

so for our example we would have an up (tranny), up or down (ds), and down (pinion) angles. the site says that both are acceptable.

it also says that pointing both the pinion and tranny up with the ds pointing down "\ / \" is unacceptable. my speculation is that this would be unacceptable since it increases the wa's and the up, down, down would be the better choice.

Tim

[gearbanger]

I understand what you are saying, and I never had really looked at it like that before.

I thought the working angles was only part of the story though. Having more to do with u-joint life than driveline vibration. I know you want at least a 1/2 degree to keep the needles rolling but if you have too much you can cause excess wear.

I thought have equal and opposite angles cancelled ocillations in the u-joints motions. You want equal and opposite angles, and if your working angles are too much, then you need to move your tranny and rear equally to reduce them.

I guess if you are stuck with a big trans angle, then maybe experimentation with reducing the working angles like you are saying would be the thing to do?

[The WidowMaker]

my speculation is that the angles are vibrating at the same frequency due to them being the same angle. i understand that its easy to think of a traditional setup as having "opposite" angles, but in fact they are the same working angle. what makes the angle opposite, and why would two opposite angles that are equal but oriented in different directions cause any vibration to cancel out any differently than two of the same angles?

i guess if you look at the setup that we're talking about, it actually has equal but "opposite" angles oriented in different directions as well.

id like to hear some more opinions.

Tim

[rockytopper]

Here is an artical from street and performance about the topic. http://www.hotrodlane.cc/ONLINETECH/drivelineangles.html as illustrated in the second pic it states you should have a max of 7 degrees if you have opposite but equal angles. \_\. That means with my engine being set a 6 degrees down I would have 12 degrees which far exceeds the max of 7 degrees.

[gearbanger]

I think it means to have your engine at 6 down and your pinion 6 up. But it all sepends on the ride height. If your driveshaft is pointed down at say 3-5 degrees then you are probably okay. But if your car is lowered then your driveshaft is probably level or even pointed up to the rear end. That is going to give you way to much working angle. So you need to raise the tail of the tranny and drop the pinion until the working angles are 3 degrees or less and the angles are equal and opposite.

http://www.minitruckinweb.com/tech/suspension/0909mt_maximized_eliminating_driveline_vibration/index.html

These are pretty good articles that explains why the angles need to be equal and opposite.

http://www.hotrodhotline.com/md/html/drive_shaft_harmonics.php

[rockytopper]

That is the path I'm on. I have raised the trans almost an inch with spacers. I now have a much smaller angle more like 4 degrees down for the engine trans. I have also been told by a very respected sponsor on here that chevelles or A-bodies sould be set up with pinion down rather than up because working angles are much smaller in the a-bodies when set up like that. Mine appears to follow that logic. I have it in the drive line shop, I think my vibration was due to a bad ujoint. I will know something this week when I get it back.

[old66tiger]

I had a similar problem and I installed adjustable control arms. The front and rear angles need to be equal and opposite of each other. I have a digital angle finder which I used to zero on the shaft as a reference. The face of the pinion and the face of the transmission should have equal angles but opposite of each other. The centerlines of each other should not diverge or intersect with each other. They should run parallel. See Mark Williams

http://www.markwilliams.com/driveshafttech.aspx