1970 GTO Version 2.0

[Bow Tie 67]

I have been dealing with adjusting the drive-line angles on my setup also. What has me going is the math. If you lower the transmount, which will increase a positive reading. Lets say from 4* to 4.5* and the drive-shaft is 2* prior to adjustment, your orig working angle is 4-2= 2*. When we lower the rear of the trans to 4.5* the front of the d.s. will lower slightly thus reducing its angle from 2* so with a larger trans angle and a smaller d.s. angle the math equates to a larger working angle when if fact you have just physically reduced the working angle.

What am I missing?

[Smock67]

Thats is certainly something i never knew. Quite interesting.

[trapin]

I'm concerned about the driveline angle on my car too. I did just as everyone said, put an angle finder on the face of the damper and lowered with drivetrain down until I had 1*. Bolted up the crossmember and installed the driveshaft and I swear the engine looks like it's angled too much in the engine cabin. But I don't know jack squat about setting up suspensions so I guess I won't know if it's a problem till I go to drive it. Until then I'll just follow along with what Andrew is doing. Good tech Andrew.

[andrewb70]

I have been dealing with adjusting the drive-line angles on my setup also. What has me going is the math. If you lower the transmount, which will increase a positive reading. Lets say from 4* to 4.5* and the drive-shaft is 2* prior to adjustment, your orig working angle is 4-2= 2*. When we lower the rear of the trans to 4.5* the front of the d.s. will lower slightly thus reducing its angle from 2* so with a larger trans angle and a smaller d.s. angle the math equates to a larger working angle when if fact you have just physically reduced the working angle.

What am I missing?

Assuming that you start with the engine UP and the driveshaft UP, when you lower the transmission it will point UP more, and the driveshaft will point UP less.

So lets say you start with 4* UP on the transmission and 2* UP on the driveshaft, so your originaly working angle is 2*.

Now you lower the transmission and it is at 5* UP and the driveshaft 1.5* UP, your working angle is now 3.5*.

Does that make sense?

Andrew

[Bow Tie 67]

Yes now it does, the only way I could see it was to put two pencils together and rotate them.

When I read the bottom of the page in the link below it states " If the front working angle needs to be decreased, lower the transmission. Keep in mind that this will also cause the front working angle to decrease." The fact is its the opposite for a car. Now take your pencils and simulate a 4 x 4 driveshaft and thats true, simulate a car and its the opposite.

Dam that was driving me nuts!!

http://www.vibratesoftware.com/html_...e_changing.htm

[andrewb70]

Right, in the truck example above, the engine started out pointing DOWN. So when the transmission was lowered, the working angle decreased.

In my car I had to raise the back of the transmission in order to reduce the front working angle. I wish I could raise it even more, but the u-joint is already very close to the floor boards. This is the reason that Troy replaced the entire driveshaft tunnel in his Chevelle. If I am still having issues, I will trim my tunnel a little further back and raise it slightly to clear the u-joint. If I went up another 1/2" on the trans I think it would be perfect.

Andrew

[Bow Tie 67]

Even if the truck engine is pointing up it will still decrease. Which is due to the fact a trucks driveshaft has a much more pronounced upward angle to begin with. Now that I think about it, a better way to explain the difference is to show the driveshaft centerline ( pivot point ). An auto has the pivot point much closer to the engine / trans centerline when viewed from the side where a truck has more distance. Here is a very crude drawing with pronounced angles to illustrate. Left to right engine / d.s. / diff.

[Code Red]

Big day today. After a rather dismal, windy day yesterday, the weather today was just amazing. I needed a little inspiration so I decided that it was time for the GTO to move under its own power. I so installed a seat, put on some wheels, cleared out the tools, and pulled it out of the garage.

Of course I couldn't resist. So I went around the block. The clutch is silky smooth. Converting from the old Z-bar to the hydraulic release was definitely worth it. The clutch actuation is just like on a modern car. Super smooth. I still don't have exhaust so the drive was short. The brakes felt solid so the MC is working well. I also noticed some noises which I think are the result of my messing around with driveline angles. I raised the back of my transmission to get the angles perfect, but now the u-joint is grazing the floor. More on driveline angles later.

Notice how much higher the front sits. I bet it's up a minimum of 2". I can't wait to get the thing scaled. I am also contemplating getting a fiberglass hood and ditching the shaker. The stock hood is probably 40-50 lbs, plus another 10 lbs for the shaker. A Glasstek fiberglass hood is probably about 25 lbs. I am open to opinions.

Andrew

I prefer the stock GTO hoods personally

[andrewb70]

Today I got the notice of approval from Grundy Insurance. On Monday I will go get the car registered and it will be legal to drive on the street. I also ordered a new 3" to 3" Dr. Gas x-pipe. This will just make the exhaust work a little simpler and cleaner. That should be here on Monday.

I had to take this picture for Tony Rapin, cause he was busting my balls about my car being orange...LOL



Andrew

[tom_a]

Andrew,

Congrats on being so close! You really make it look easy dude.

I don't want to get to off topic on your thread...but I am trying to learn from your prior post on driveline angles. Keep in mind this is more academic as I realize things will change with the body on.
I bought a digital level from Home Depot that states accuracy +/- .1 degree. *Sorry for the crappy cell phone pics
What I did not realize was there is no option to use a 90 degrees. So transmission came out 88.8 down \ which comes to 1.2 degrees

The rear came out at 87.2 / which comes to 2.8

So if I am calculating correctly I have a 1.6 working angle?
FYI: I don't have a driveline yet and as we discussed I am considering doing the tunnel mod that Troy did....I don't really want to but I hope to set the body on this weekend just to get a better feel.

Thanks,

[subtlez28]

I had to take this picture for Tony Rapin, cause he was busting my balls about my car being orange.

FWIW
I like it in orange!

Great progress Andrew!

You should bring it up to a race a Autobahn this year!

[andrewb70]

Tom,

You need a driveshaft to determine the working angle. If I was building my car from scratch today, I would make it so the engine and transmission are level to the frame. This would most certainly necessitate the need for modifying the transmission tunnel.

Andrew

[tom_a]

Thanks.

Tom

[andrewb70]

FWIW
I like it in orange!

Great progress Andrew!

You should bring it up to a race a Autobahn this year!

Shaun,

Do you have a link for a schedule of events?

Andrew

[subtlez28]

http://www.mcscc.org/events.php

May 24 - 25- 26 Blackhawk Farms Lapping Day - W2W - HSAX
June 7 - 8 Autobahn CC North HSAX / Race
June 28 29 Blackhawk Farms HSAX / Race
July 19 - 20 Blackhawk Farms Driver School / Race
Aug 9 - 10 Blackhawk Farms HSAX / Race
September 20 - 21 Blackhawk Farms HSAX / Race
October 4 - 5 Autobahn South HSAX / Race

[andrewb70]

I was going through some old paperwork this afternoon and I found my old corner scale sheet. Here are the numbers with driver:

[Front Left]-------------------------[Front Right]
1218----------------------------------1153



[Rear Left]---------------------------[Rear Right]
929------------------------------------884

Total Weight = 4184

56.7% front
43.4% rear

Andrew

[subtlez28]

Cool to see the scale #s!

I definately want to corner scale my car b4 I take it apart. I wish I had done it stock. W/ the iron intake, AC stuff and big crash bumper hanging on the front.

I was hoping the L92 and other lightening would bring the weight down to at least near the weight of my Camaro (3600 w/ driver), or hopefully less. But these #s worry me. I realize your car had the big block, but I would think a 70 would be lighter, and you had aluminum heads/intake, and no A/C, right?

On the plus side the front/rear balance isn't bad for a big block a-body. My LS1 4th gen has a 56.1%/43.9% split. So I still hope to better the 4th gen in the balance department. And of course more rubber, and more HP!

[Rolling_Thunder]

Damn that is a heavy car... i didnt know goats were heavy hitters... I corner scaled a customer's 71 Challenger with a 528 hemi and a 5-speed with driver and it came out to 3210lbs

Good to see the progress man!

[trapin]

I'm sure he'll be under 4K now that the big block is gone.

[andrewb70]

Damn that is a heavy car... i didnt know goats were heavy hitters... I corner scaled a customer's 71 Challenger with a 528 hemi and a 5-speed with driver and it came out to 3210lbs

Good to see the progress man!

Keep in mind that is with driver. The car was 3933 without my fat ass in it. Also keep in mind that there is about 100 pounds of sound debtner in this car, and about 100 pounds of sub woofer and amp. I wish I could remember how much gas it had when it was initially weighed.

I will be very happy if the car is about 3600 pounds now, with a much better weight distribution.

Andrew