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Old 01-25-2017, 05:54 AM
OZgreen69 OZgreen69 is offline
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Default One day.... It will be a race car!

Hello,

I would like to show you what I am doing at the moment.

Fan of historic car racing, I am building/assembling/modifying, a 69 convertible to do just that here in Australia.
The rules of the group that the car will be into, are quite restrictive to keep the spirit of club racing alive ( Yeah right !! )
For example, no alloy heads ,or original gear box only, interior trim and a passenger seat must be retained , original kind of suspension . Well, all done to slow you spending too much ( Yeah right !! )

So I have been collecting bits and pieces along the way like :
A 69 coupe who was going to be a race car in 2003 for historic racing as well, but instead to be pushed unfinished in a dark corner of a workshop and left there until last year when I bought it as a rolling chassis.
As the frame as been prepared in the Chevrolet Power Book fashion, I thought about reusing it for my race car.
The previous owner modified it using few Guldstrand parts.
Solid pucks for the rear cross member and adjustable toe system for the trailing arm and more....

Last edited by OZgreen69; 05-17-2017 at 11:16 AM..
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Old 01-25-2017, 06:38 AM
OZgreen69 OZgreen69 is offline
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So talking about the frame.
The diff as been raised, or the chassis lowered onto the diff, choose the one you like, by removing the rubber mounts and using solid spacers instead.
Nice job until I tried to align the diff pinion in relation to the gear box :confused : and
It was necessary to cut the cross member brackets on the frame to be able to pivot the nose of the diff to a more correct position . I had 3 deg Down to now 1 deg Up more in line with the gearbox tail at 1.20deg Down.
Anyway, a bit anxious with the pinion height , I put the body on the frame to see that I have no room for the drive shaft to clear the floor and for the stub axles to touch the rear compartments !!

Does someone else did this mod?
Any help, ideas, welcome.


I have some difficulties uploading pictures, does TT thread still up to date ?
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  #3  
Old 01-25-2017, 01:17 PM
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BBShark BBShark is offline
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Looks like the tape measures (from your picture) 4 3/4. I measured mine at about 2 inches. Hard to measure with the drive shaft in. My diff is down 1.3 degrees at the pinion with 1/4 spacer and no modification to the crossmember mounts.
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Old 01-25-2017, 02:40 PM
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rtj rtj is offline
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Raising the diff may require cutting and redoing the driveshaft tunnel. Most lowered cars seem to have this done.

We probably need a thread with links to builds like these

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Last edited by rtj; 01-25-2017 at 02:44 PM..
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Old 01-25-2017, 05:37 PM
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redvetracr redvetracr is offline
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when you get rid of all that rubber in the pinion mount you will be just fine.
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Old 01-26-2017, 12:17 AM
OZgreen69 OZgreen69 is offline
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Thanks for the replies.

BBshark , do you mean that you haven't modify anything ?
And that the pinion angle of the diff is still quite as per factory, roughly 1 degree down and the gearbox looking down as well ?

I went to a reputable driveshaft specialist to talk about drive shaft angles and especially about the W configuration, who is working well at low angles but mainly used on machinery rather than car. Their concerns were about the revs , low on machinery but high on cars. I am still waiting on their computer simulation.

RTJ, well this is that I would like to avoid, starting to modify the body. I looked at period pictures of racing Vets. And you can see clearly that few bodies are higher up on their respective frames, the side holes are a good measure.

Or maybe I just need to have a drive shaft with a CV joint gearbox side ?? As seen on another forum. But the drive shaft guys were not too keen because of the movement of the slip joint and the movement of the CV.

Anyway, the drive shaft angle is the question. From the factory the angles were in a W . Diff down AND gearbox down and no apparent vibration. If I can replicate this I am saved.
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Old 01-27-2017, 11:31 AM
OZgreen69 OZgreen69 is offline
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I spent more time in the w/shop doing different angle combinations.
So following BB's description and reading between the lines of Redvet reply.

I lowered the pinion nose back to a near factory 1.25 Deg down and G/box at the same angle and with a D/shaft going up the diff at 0.5 Deg, this give me according to SPiCER calculator, an operating angle of 1.75Deg for both.
This will be a W configuration.
I need to dig a bit further to see if this is ok or not.
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Old 01-27-2017, 11:52 AM
OZgreen69 OZgreen69 is offline
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Thanks RTJ for the links, but I am not allowed to do what they do, especially like P Klutt !!! Still nice to see and who knows in the future !!
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Old 01-27-2017, 02:17 PM
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The angle just needs to be the same on both ends. I measured the trans yoke angle and adjusted the pinion spacer to match.
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Old 01-27-2017, 08:56 PM
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You can see the spacer in this picture. The 1/4 rotates the pinion/diff down a little more than 3/4 degrees You can tell from looking at it that is pretty close to the frame bracket. My diff is down 1.4 degrees. The drive shaft is down (at the rear) .8 degrees and the engine is down (at the trans) 3 degrees. This gives me 177.8 degrees between the engine and driveshaft and the same between the driveshaft and diff.

I will almost certainly have to raise the tunnel at the transmission so I may look into raising the crossmember. Not sure which is more of a hassle.

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