Prop shaft considerations

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Phil Riley
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Prop shaft considerations

Post by Phil Riley »

If you're making your own prop shaft and setting up diff and box this video might be useful:

https://www.youtube.com/watch?v=5aCK4Bob6a0
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Roger King
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Re: Prop shaft considerations

Post by Roger King »

Good video, Phil - driveline geometry is critical. I spent several days measuring angles and welding spring brackets on my Mustang to get mine as good as I could, having fitted a different gearbox which sits at a slightly different angle from the original.
However, for most Hawks, Kirkhams and others there is very little you can do about propshaft angles as both engine/gearbox and rear axle unit are rigidly (virtually) mounted and there is no adjustment available other than cutting off mounts and rewelding them. I did look long and hard at the DL angles on my Hawk with the thought of improving them, but it would have required massive surgery to do so. It's also worth noting that the propshaft itself is so small and short that any likely vibration issues caused by poor alignment are dramatically reduced. The Mustang's is over 4ft long and has no Plummer block, which gives much greater potential for vibration.
So, I left it all where it was!
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Fireball
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Re: Prop shaft considerations

Post by Fireball »

Thanks for that Phil, I've got exactly that issue with a misalignment of engine to diff. I was hoping to change the gearbox to a narrower Tremec T5 and drop the gearbox therefore allowing a straighter alignment but it looks as though the plane of the input yoke has to be in the same plane as the diff flange. At least I know why the bush in the back of the gearbox has worn. :(

James
Finally sorted Dax 'AC 289' after 4 years in the wilderness.
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Roger King
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Re: Prop shaft considerations

Post by Roger King »

Driveline input and output angles should ideally be within 3° of each other, but as said it's very difficult to change this in a Hawk.
It wasn't the height discrepancy that worried me so much with my Hawk, it was the lateral (horizontal) location as the diff unit input is off to one side necessitating quite a high UJ working angle. Again, there's no easy fix for this.
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Fireball
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Re: Prop shaft considerations

Post by Fireball »

Hi Roger, I also have an offset with a Jag back end. I was going to twist the horizontal angle of the engine to straighten it up but it looks as though that isn't my answer after seeing the video.
Finally sorted Dax 'AC 289' after 4 years in the wilderness.
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Roger King
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Location: St Ives, Cambs

Re: Prop shaft considerations

Post by Roger King »

Fireball wrote:Hi Roger, I also have an offset with a Jag back end. I was going to twist the horizontal angle of the engine to straighten it up but it looks as though that isn't my answer after seeing the video.
Not the answer, James! This is really one of those 'black art' areas with no set 'right' answers.

This gives an idea:

http://www.hotrod.com/articles/91758/

BUT remember that these are all US builders, working on cars with live axles - Cobra diffs are rigidly mounted and cannot move!!
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