1 PC, 2 PC driveshaft. What's the Diff? - IMBOC
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post #1 of 7 (permalink) Old 05-20-2019, 04:17 PM Thread Starter
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Talking 1 PC, 2 PC driveshaft. What's the Diff?

Rosebud posted a query today about one piece aluminum driveshafts. A timely post since I'm writing about driveshafts today. Hmmmm?
Let's start with the basics. Universal joints like to operate on a 1-3 degree angle, 2 degrees preferred. If the angle is greater or less than recommended, then you will cause early wear or failure of the u joint, driveshaft yokes, or the pinion bearings and gear.
The 2001 and 2008 Bullits have two piece steel driveshafts. This allows for smaller angles on the yokes, u joints and pinion. The downside is that they are quite heavy and clunky because of all the movement of four u joints and a hangar bearing.
If you change to a one piece aluminum driveshaft, you reduce the weight by about 10-20 pounds and therefore reduce the rotational mass and can modestly improve acceleration and shift quality.
The good aluminum driveshafts will usually just bolt up to the existing pinion flange and plug into the back of the transmission, and have a booted slip joint. A 3.5" diameter shaft is ideal (some are 4") because that diameter will usually not contact the floor of the car even if it is lowered a bit. (read ~1")
Here's the concern. The pinion angle and the trans. output shaft angle should be equal and opposite for best operation. Example: Pinion angle negative 2 degrees (up), trans. output shaft positive 2 degrees (down)
If there is a large difference, then you bind the u joints and lose power. The reason you want ~2 degrees angle is so that when you take off and the suspension squats, then hopefully you zero out the angle.
But how can you adjust the pinion and Trans. shaft angles? If you have adjustable UCA's and LCA's then you can rotate the axle slightly and dial in the angle. If no to the adjustable control arms, then you can shim the rear trans. mount a bit to help out the angles. Hopefully you can get the two angles close to equal (within 1 degree) and opposite within the 1-3 degree angle which will optimize your power delivery and u joint life. If you don't, you will likely wear out the rear u joint prematurely and put extra strain on the pinion gear and bearings. Unintended consequences await you with every modification.


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post #2 of 7 (permalink) Old 05-20-2019, 07:47 PM Thread Starter
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post #3 of 7 (permalink) Old 05-20-2019, 08:45 PM
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Once again, great info!
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post #4 of 7 (permalink) Old 05-20-2019, 10:01 PM Thread Starter
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Thanks Paul
The angles should be measured in static position, weight on the wheels. So you need a drive on hoist or 4 jack stands, 2 under the rear axle and 2 under the front control arms.
The idea is to have the driveshaft "horizontal" or "zero'd" out under acceleration.


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post #5 of 7 (permalink) Old 05-20-2019, 10:18 PM
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DSS 1-piece driveshafts have a CV joint at the rear, and are therefore not sensitive to pinion angle changes due to lowering the car.

"No pinion angle adjustment is necessary when using a Driveshaft Shop driveshaft and we strongly discourage it."

https://www.driveshaftshop.com/domes...earance-issues

.
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post #6 of 7 (permalink) Old 05-20-2019, 10:30 PM Thread Starter
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That's definitely a way to go. They certainly have a great deal of choices depending on which model you have.


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post #7 of 7 (permalink) Old 05-21-2019, 11:35 AM Thread Starter
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