[gearbanger]

Also, mine is 3.5" steel. If you do an aluminum, I would have it sized smaller in the last 12" or so if you can, because mine wants to hit right at the back of the back seat tray, right where the rear seat bottom catch is in a hard bump like right on the bumpstops. The stock driveshafts were stepped in the back this way. Again, 70 may be different. I did not do aluminum because usually you have to go a size bigger in aluminum to keep the strength and I knew I did not want any more clearance issues.

[andrewb70]

Originally Posted by gearbanger

Andrew, I had my driveshaft made by inland empire driveline when I did the TKO swap. Then when I had it off the frame I switch my pinion yoke to a 1350 U-joint so I had to shortn the driveshaft 1/2". I found a driveshaft shop in Glasgow KY call precision driveline. As soon as I walked into his shop I knew he was the guy I wanted to work on my car. Everything was so organized and clean. He had a driveshaft spin balancer and he checked it for runout in three places and he actually said it was kind of bad. It seems like he said it was about .005 out at one end or something? Its been a while so don't quate me on that. He said what the tolerance was and I remember that it was just outside the tolerance. But most vehicles are not beind made to run at 100+ mph. At any rate, it took him about 30 minutes and he was done, fixed my runout problem, shortened it .5", and balanced it for $40! I though that was awesome.

So anyway, I am hoping that was the problem. I havent had it out at any speed yet to see bu I will report back as soon as I can.

Look at post #156 in this thread. Do the pictures look familiar? LOL

Keep me posted. I am curious to see how you do with your vibration issue.

Andrew

[HWYSTR455]

You know, that's a very good point, many shops balance using the 60 mph sweet spot, and in many case that isn't even close. I know there are some cheaper balance machines that don't have as good a tolerance either, and I had to scout around to find one that will balance to my liking.

I think you may be over-engineering this issue, (something I'm guilty of regularly!), and is probably simpler than all this. Call Denny's or Inline, or Dutchman, any should be able to give you a lot of info. I would also stick with 1350s by the way.

I still say that diag tool that uses the harmonic freq to point you in the right direction is the ticket. That gets away from looking at it from a just angles point of view.

.

[andrewb70]

Originally Posted by HWYSTR455

You know, that's a very good point, many shops balance using the 60 mph sweet spot, and in many case that isn't even close. I know there are some cheaper balance machines that don't have as good a tolerance either, and I had to scout around to find one that will balance to my liking.

I think you may be over-engineering this issue, (something I'm guilty of regularly!), and is probably simpler than all this. Call Denny's or Inline, or Dutchman, any should be able to give you a lot of info. I would also stick with 1350s by the way.

I still say that diag tool that uses the harmonic freq to point you in the right direction is the ticket. That gets away from looking at it from a just angles point of view.

.

I am going to work with Frank at the Driveshaft Shop. I have dealt with him on some custom axles for my RX7 project. He also just got a new balancing machine that will balance a shaft up to 9500RPM. He has been working with some NASCAR teams to address some of their issues.

I may have to stick with the 1350 u-joints, since there are yokes available to use CV joints. Although, the CV joints are a very elegant solution. They are used extensively on cars that are made to run at very high speeds for sustained periods of time. On the other hand, 1350 u-joints are used on trucks...just saying...LOL

Here is a link to the 2005+ Mustang driveshaft that Frank is coming out with:
http://driveshaftshop.com/blog/?p=440

Andrew

[HWYSTR455]

Ok, I have to admit, I haven't gone through all the posts regarding the vibration issue, though over this weekend, I will. I just got back from New Orleans, and trying to catch up here at work...

I did see on post 160 you mention there .038 run out at the shaft, and that's enough to cause a vibration I believe. You say the rear is pretty fresh? You've double checked the pinion and carrier bearings? Figured you have, but asked anyway!

I went through a little chase-my-tail initially with my vibration issue, since the pinion yoke took out a u-joint, replaced that, took out a tailshaft bushing, replaced that, and also took out a pinion bearing. By this time I had to replace the u-joint again. Maybe you're just suffering a little of the same karma, have to do it all at once or something? Just taking a stab, and sure at some point the light will come on and you'll go "Oh yeah!" and knock it out.

I'm curious, let me know when you do figure it out, will make a mental post-it note. If something comes to mind over the weekend after going through all the posts, I'll post any ideas.

.

[gearbanger]

Originally Posted by andrewb70

Look at post #156 in this thread. Do the pictures look familiar? LOL Andrew

HAAAAA! That is helarious! He is a pretty good guy isn't he! So did your driveshaft have .038 runout? That is a bunch! Did he leave it that way or what was the deal?

I will definitely report back soon on it. I agree that u joints are such an archaic way of doing it, but it is strong. I don't know if cv joints can take the kind of abuse that a stick shift launch puts on a joint. Is there more stress on a driveshaft joint or a half shaft going to the wheel? Seems like there would be more torque on a half shaft, but maybe less impact do to gear reduction?

[Motornoggin]

Andrew,

Just read through most of this thread. It's neat to see the progression all right here lined out and easy to follow.

Knowing the overall story of your GTO since you first got it and we first became friends, I hafta say just how proud I am of you and how far you've come over the years!

Kudos to you my friend.

Talk to you soon.

Rory

[andrewb70]

Originally Posted by gearbanger

HAAAAA! That is helarious! He is a pretty good guy isn't he! So did your driveshaft have .038 runout? That is a bunch! Did he leave it that way or what was the deal?

I will definitely report back soon on it. I agree that u joints are such an archaic way of doing it, but it is strong. I don't know if cv joints can take the kind of abuse that a stick shift launch puts on a joint. Is there more stress on a driveshaft joint or a half shaft going to the wheel? Seems like there would be more torque on a half shaft, but maybe less impact do to gear reduction?

My driveshaft didn't have .038" runout. I got that measurement when the shaft was mounted in my pinion yoke. I replaced the yoke and that greatly improved the total runout as measures when the driveshaft was mounted in the yoke. I am going to upgrade my pinion yoke to a billet one from Mark Williams.

The 108mm CV that The Driveshaft Shop uses can handle over 7000lb/ft of torque. That's about the same as a 1350 u-joint. Torque capacity should not be an issue.



They use the CVs for various late model cars like the 5th gen Camaros.



Andrew

[andrewb70]

Originally Posted by Motornoggin

Andrew,

Just read through most of this thread. It's neat to see the progression all right here lined out and easy to follow.

Knowing the overall story of your GTO since you first got it and we first became friends, I hafta say just how proud I am of you and how far you've come over the years!

Kudos to you my friend.

Talk to you soon.

Rory

Thank you Brother!!! I need to get my GTO back on the road and come visit you.

Andrew

[Motornoggin]

Originally Posted by andrewb70

Thank you Brother!!! I need to get my GTO back on the road and come visit you.

Andrew

That would be great! You're always welcome my friend!

[gearbanger]

So, would you have a CV joint in the back too or just the front? Seems like you are still going to have to deal with at least some slop introduced into the driveline by the splines and the slip joint at the trans. If that is the source of our problems, then we may be screwed.

I guess I just always thought it was a wheel and tire balance issue. I mean, these guys at these shops just balance your tires at like 30 mph and thats when they are new, a couple of burnouts later, they have to have changed. IMHO

[gearbanger]

Originally Posted by HWYSTR455

I have never heard of a driveshaft's weight being an issue when it comes to balance, Did the same guy balance all your driveshafts? Maybe just for sake of elimination, try someone else?

I don't know alot about driveshaft balancing, but by my calcs, the driveshaft is cranking over 3300 rpms at 75 mph. That is assuming a 28" tall rear tire. So I could see where that would create a vibration if everything wasn't koser. And the heavier the driveshaft the more problem a little slop would cause. It would be cool to throw another driveshaft in it, escpecially a lighter aluminum one just to see about the vibration issue would change.

[andrewb70]

Originally Posted by gearbanger

I don't know alot about driveshaft balancing, but by my calcs, the driveshaft is cranking over 3300 rpms at 75 mph. That is assuming a 28" tall rear tire. So I could see where that would create a vibration if everything wasn't koser. And the heavier the driveshaft the more problem a little slop would cause. It would be cool to throw another driveshaft in it, escpecially a lighter aluminum one just to see about the vibration issue would change.

My tires are 27.3" tall. The vibration really starts becoming noticeable as the driveshaft speed approaches 4000 RPM. I've exchanged more emails with Frank over the weekend, and I am pretty set on having him make a shaft with a CV in the front in either aluminum or CF.

Andrew

[gearbanger]

How does the cv attach to the slip yoke? And is there a special pinion yoke that bolts to the pinion and bolts to the CV?

[andrewb70]

Originally Posted by gearbanger

How does the cv attach to the slip yoke? And is there a special pinion yoke that bolts to the pinion and bolts to the CV?

Frank is going to modify a standard slip yoke by machining it down and welding on a cup for the CV. He said that he has done this many times and there are no issues with durability. On the pinion side I am swapping over to a Mark Williams 1350 billet yoke. With the CV joint in the front the front angle doesn't matter. The CV can operate at angles as high as 40 degrees without issue. In the rear I will adjust my upper control arms so that the rear working angle is minimal, just a hair more than zero. Problem solved!

Today I actually told Frank to move forward on this project. He will make me the yoke and I will mock it up for proper driveshaft length.

Andrew

[gearbanger]

So you are thinking that it is too much working angle of the u-joints then that is causing the vibration, and not the driveshaft being out of balance?

So it seems like a really good plan. What material for the driveshaft? What diameter?

[andrewb70]

Originally Posted by gearbanger

So you are thinking that it is too much working angle of the u-joints then that is causing the vibration, and not the driveshaft being out of balance?

So it seems like a really good plan. What material for the driveshaft? What diameter?

Honestly, I don't really know the exact cause of the problem. I am taking a shotgun approach to the problem. My transmission will be rebuilt, and a new, driveshaft will be made with the CV joint. I am also changing the rear yoke. I am hoping that the combination of all those things will solve the problem. Right now I am leaning towards a carbon fiber driveshaft, 3.25" O.D.

Here are some neat details about the CF shafts:

http://driveshaftshop.com/blog/?p=546

My shaft will look very similar to the 2010 Camaro driveshaft.

Andrew

[gearbanger]

I don't think you are taking a shotgun approach. You have eliminated most of the elements of the car in a very scientific manner to a few remaining components. It is too bad though that you will be replacing several components at once. You won't really know which one fixed it that way, but hopefully it will be fixed and that is all that matters anyway.

[6 Grrrs]

I am interested in your results. I have been fighting a vibration in my pickup for years. I would be very interested in doing the cv joint setup if it works.

[andrewb70]

Originally Posted by gearbanger

I don't think you are taking a shotgun approach. You have eliminated most of the elements of the car in a very scientific manner to a few remaining components. It is too bad though that you will be replacing several components at once. You won't really know which one fixed it that way, but hopefully it will be fixed and that is all that matters anyway.

Unfortunately its not possible to replace components individually. For instance, when my transmission failed, it took out my Strange billet slip yoke. It would be an extra expense for me to install a new yoke, change the rear yoke, have the old driveshaft rebalanced, and then test the results. I would much rather put those funds towards the new driveshaft. I am really excited about this. The vibration issue has plagued me for so long that I have almost given up on it. I have a feeling that it will feel like a completely different car.

Andrew