1970 GTO Version 2.0

[csouth]

There have been various discussion on several forums that I frequent regarding driveline vibrations, angles, etc...



In one of the posts, I made the comment that just about every modern, rear wheel drive, performance car uses CV joints for the driveshaft. We spent all kinds of stupid money to buy the latest engine, transmission, and suspension parts, but when it comes to our driveline components, we still use u-joints that date back to the 19th century. I have used a CV driveshaft with great success, but the optimal solution would be to use a driveshaft that uses a CV joint at both the transmission end and at the pinion. So I called Frank at The Driveshaft Shop to discuss this further and after telling him all this he starts to laugh. Then he proceeds to tell me how he just made a batch of pinion yokes for the Ford 9" and the Chevy 12 bolt rear ends that will accommodate a 108mm (Porsche 930 style) CV joint. He sent me the picture below:



That particular yoke is for the Ford 9" rear. What this means is that if someone wants the ultimate solution for a driveshaft, this is it. Using CVs at both ends of the driveshaft means that driveline angles become largely irrelevant. The CVs can accommodate up to 9 degrees of articulation and the front and rear angles operating don't have to match, be opposite, or be as small as possible.

Andrew

Nice piece! Are these readily available for sale?

[andrewb70]

Nice piece! Are these readily available for sale?

Frank said that he has them in stock.

Andrew

[jerome]

I have used a CV driveshaft with great success, but the optimal solution would be to use a driveshaft that uses a CV joint at both the transmission end and at the pinion.

Andrew - can you explain why you would need a CV joint at the pinion end of the driveshaft? Of course a CV joint at the transmission joint is useful, because packaging constraints sometimes force front u-joint operating angles to be larger than 3 degrees. However, I can't think of any rear suspension setups where pinion angle isn't adjustable. I understand CV joints are still stronger than 1350 u-joints, but if a 1350 is sufficient and you can get rear operating angle to less than 1 degree, why would you spend the extra money for a rear CV joint?

[andrewb70]

Andrew - can you explain why you would need a CV joint at the pinion end of the driveshaft? Of course a CV joint at the transmission joint is useful, because packaging constraints sometimes force front u-joint operating angles to be larger than 3 degrees. However, I can't think of any rear suspension setups where pinion angle isn't adjustable. I understand CV joints are still stronger than 1350 u-joints, but if a 1350 is sufficient and you can get rear operating angle to less than 1 degree, why would you spend the extra money for a rear CV joint?

In a static configuration (car at rest) you're absolutely correct. However, we know that cars are driven and when forces are applied to the rear axle the pinion will have a tendency to rise. How much or how little depends on the suspension design and the bushing material, but the pinion can move a surprising amount. Also, under various conditions it can move a lot or adjust a little, based on how much power is being applied. So while it is fine to set-up the pinion angle so that the rear u-joint working angle is less than 1 degree (this is what is recommended with a from CV joint) it is difficult to dial that angle in under a wide variety of conditions. With the CV at the pinion, the amount of pinion climb become largely irrelevant.

Andrew

[raustinss]

I search the website and nothing was a there, I emailed the driveshaft shop and was promptly replied to. The pinion yoke is in stock and in the case of the 12 bolt rearend its price is 199.99$ probably safe to assume that the ford 9" would be a similar price. I also asked what a very rough price would be for a gm A body carbon fiber driveshaft with cv joints at each end. If you want to know what the price is pm me. As I don't want anyone on here calling up the driveshaft shop and trying to hold them to a price that was intended for me and I did state a very rough price. It's not that I don't trust anyone but I think it's just the best way to prevent problems.
Regardless I will be taking a page from Andrews gto and going the same route for my chevelle
Ryan Austin

[Mr.VENGEANCE]

oh shoot, Andrew putting in work!

[INTMD8]

That CV pinion yoke is super nice!!!

[andrewb70]

That CV pinion yoke is super nice!!!

I wish Frank had it available when I got my driveshaft made.

Andrew

[andrewb70]

Well...just like many of you, I can't seem to leave it alone. I am all moved to my new place and I finally have a garage again. I decided to do a little tinkering with the sub and did a little experiment...see link...

https://www.pro-touring.com/threads/...Sub-experiment

After goofing around with the MicroSub, I decided to really take a look with my existing set-up. I discovered that the rear package tray was not exactly solid. The "professionals" that installed the box in the first place, cut out a huge square section right out of the middle, which really weakened the package tray. This isn't so much of an issue, unless there is a 50 pound box with a substantial sub attached to it. I am quite certain that the whole package tray used to move around quite a bit, which isn't exactly ideal. Also, I found that the box itself wasn't well made. Part of it was made of MDF, while another part was made of regular particle board. Also, instead of installing a proper terminal, they simply made a hole in the box, passed the wire through, and called it a day. No silicone...nothing...not even gum.



On a brighter note, once I pulled the sub, I realize that it was a Diamond Audio M6...and not a M3 as I originally thought. This was the top of the line sub back in the day and has dual 500w 4 ohm voice coils.



At least they wired it properly for a 2 ohm load. The other good news is that the box is the right size for the driver. Diamond Audio designed these subs to work in fairly small sealed enclosures, around .75 cubic feet. I took some measurements and after a few calculations got .72 cubic feet, after taking the volume of the driver into account. The good news is that with a little TLC, I think I can reuse this box. It is just the right size to fit on top of the hump that GM A-bodies have in the trunk and obviously the volume is right.

So now the questions...

Would it be better to point the driver towards the rear?

Would it be better to point the driver towards the rear seat back?

Any suggestions for anchoring this thing?

I am also quite certain that I am not driving this bad boy with enough power. Right now it is getting 350 watts, and that's just not enough. I bet the driver isn't even broken in.

I did pick up a used Xtant 601 a while back, so I am tempted to use it for the sub.

All comments and suggestions are welcome...

Andrew

[andrewb70]

In short, FML.

I spent about 6 hours doing this:



Only to try this afterwards:



What look like cheap ass 12" Kenwoods totally rocked...If only I had done that first...as I said, FML.

Andrew

[csouth]

I had some diamond d2's and they didn't hit as hard as I expected them to. I'm going to put my JL audios in whenver I get to that point in my life...lol

[andrewb70]

I had some diamond d2's and they didn't hit as hard as I expected them to. I'm going to put my JL audios in whenver I get to that point in my life...lol

Today I actually put the box with the Diamond in the same position as the Kenwoods and it sounds pretty good. I am contemplating building a fiberglass box that will fit snugly behind the seat towards the passenger side and fires the driver to the rear. This sub only requires a .5-.75 cubic foot box, so it should be nice and tidy.

Andrew

[andrewb70]

I scratched the fiberglass box idea. Instead, I decided that it would be simpler and easier to build a shelf behind the seat that would support the sub on the passenger side and allow for space for the amp on the driver's side.

Here is what I came up with. It isn't super pretty, but it will do the job. The trunk of my car was never meant to be a show piece, it is there to haul crap.



The shelf is 1/2" MDF and is supported by the hump in the middle and some trimmed down 2x4s on the edges. The 2x4s will be attached to the trunk divider and the sub will be anchored to the bottom of the package tray. Should be pretty solid.

Here you can see where the amp will go.



There will be ample space all around it for cooling and all the wires will come in from behind and underneath and should look pretty clean.

I even decided that I should make everything a little prettier and wrapped the sub in black felt and I will do the same for the shelf.



Stay tuned for more, as I just placed an order with Don at Sound Deadener Showdown

This is turning into sub/interior sound deadener redo...

Any comments and suggestions are welcome as always.

Andrew

[andrewb70]

Today I wrapped up the sub-woofer installation. It's really a pain to work so deep inside the trunk. Luckily I had the rear seat out and I could get at some of what I needed to do from inside the passenger compartment.

Here is a shot of the shelf after I wrapped it with some felt:



All of the wiring for the amp goes under the shell and is tucked towards the back.

Here is the final product.



I've also been playing around with making videos for those of you that prefer that sort of thing...



All questions and comments are welcome as always.

Andrew

[pist0lpete]

Andrew unlike the driveline issues you chased it appears you have the "good vibrations" going now. Sorry I couldn't resist...

[redsand]

Hey Andrew. I know this will be a pain but I would dynamat the entire rear trunk or at least part of the back taillight section....You dont want to be that guy that when you drive by all you hear is the taillights rattling from inside the trunk...plus you will be very suprised how well the bass will hits after you do that. Dont remember the specs on that sub but it also might sound better if someone builds you a tuned ported box. You could then depending on the port size / length route it up through your hole in the package tray and not have to worry about any rattles in the trunk. Just not sure if that sub model is more efficient in a ported box or not.

[andrewb70]

Hey Andrew. I know this will be a pain but I would dynamat the entire rear trunk or at least part of the back taillight section....You dont want to be that guy that when you drive by all you hear is the taillights rattling from inside the trunk...plus you will be very suprised how well the bass will hits after you do that. Dont remember the specs on that sub but it also might sound better if someone builds you a tuned ported box. You could then depending on the port size / length route it up through your hole in the package tray and not have to worry about any rattles in the trunk. Just not sure if that sub model is more efficient in a ported box or not.

I ordered CLD tiles just for that purpose. There are already large patches of CLD (Cascade Audio V-Max) on the inner side of the rear quarter panels, but more will be added inside the trunk area. The tail lights and the trunk are definitely rattling some, and that will be addressed.

Andrew

[andrewb70]

Yesterday I tackled another project. Since I removed the subwoofer from under the rear package tray, I was not faced with having a hole in the rear package tray trim piece. I had some nice vinyl that I had purchased a while back, so I decided to cover the package tray with it. The end result wasn't perfect, but I think it turned out pretty well..

Follow along:



Andrew

[Mr Nick]

Is that an access panel for a fuel pump? I need to build something like that as well...

Attachment 100238

[andrewb70]

Yes it is...It comes in very handy when the fuel pump needs to be serviced.

Andrew