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Replacing the center u joint

1542 Views 1 Reply 2 Participants Last post by  CarolPPV
Has someone posted a procedure to replace the ujoint or the support bearing?
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Consider a one piece aluminum driveshaft
OEM two = 36 pounds
aluminum driveshaft =18 pounds
  • G8 or Caprice, no difference in the physics involved.
We have been told that you can get 6 to 8 horsepower to the rear wheels just by doing a shaft change from steel to aluminum."
Going from steel to aluminium drive shaft will reduce component weight and it may also reduce rotational intertia depending on the design (but it ain't huge).

Obviously reducing inertia will improve throttle response but it can't improve on torque or horsepower as the engine combustion efficiency hasn't changed at all as the engine hasn't been touched... More of the available torque can be used to accelerate the vehicle (rather than be sapped accelerating the gearbox shafts, drive shafts and wheels).

You will even see a hp increase on a dyno but that's just a perceived hp increase. It's just like stripping out the vehicle's interior and then running a 1/4 mile where you'd get a faster times though the engine is exactly the same as before and producing exactly the same hp....

Obviously with low rotational inertia, a component can be accelerated more quickly for a given horsepower but the steady state power level the engine produces hasn't changed at all.

Put another way, its like the age old equation of f=ma (or a=f/m)... for a given force (engine), reduce mass (vehicle weight) will always result in higher acceleration (1/4 mile time). Rotational inertia is much the same though the formula is more complex. However, technically it's wrong to say you have more horsepower...

(guess its just another case of dumbing things down by marketing at the expense of science. It's why we've seen larger diameter wheels with every model release... cause they look cool and peole want them... yet rotational inertia of said wheels has been growing higher which can't be overcome by now changing driveshafts to alloy)
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