Which is stronger 3rd gen alum or 4th gen alum drive shaft.
I am doing a t56 swap and have 3 drive shafts total. An original 85 steel shaft, 3rd gen aluminum and 4th gen aluminum. The 3rd gen AL one feels heavier and more solid, has a thud when you tap it. the 4th gen AL one feels like a Coke can and rings when you tap it. I saw somewhere that some people prefer the 3rd gen because it is stronger. Just want to get some opinions about this... I dont want to shred the 4th gen one like alot of people say they have although I'm probably only putting down 280hp ish...

 

As you have found out, 3rd gens have thicker wall but smaller diam, 4ths have thinner wall but larger diam.
I've seen more 4th gen ones twisted but was it because of more power/shock? Not sure. I'd run the 3rdgen. Pick your poison and swap it if it breaks.

 

3rd gen

 

Thanks for the input. I think I will go with the older one.. maybe sell the 4th gen one...

 

Didn't the LT1 cars get the same design driveshaft as the thirdgens? Could be wrong but I thought the redesign came about with the LS1.

 

I bought a new 3rdgen style aluminum DS in late 96 so I'm pretty sure you are correct in thinking around 97-98 the change was made.

 

At your power level it really isn't going to make much of a difference which one is "stronger"

As far as I understand though the larger diameter tube increases the driveshaft critical speed. So there is less possibility of failure from operating RPM, all things being equal. I also think that translates to lower chance of vibration.

 

I've seen failed LS1 shafts in person, and numerous pictures of them online, I am confident they used the same thin-wall cardboard damped shorter-shaft, longer-yoke units basically 98-02. All manuals, some automatics.

A late friend ran a 10 second (at 1 mile altitude) car with 4 speed, using a 3rd gen shaft and big slicks (it fit, it worked, and it had a Chrysler yoke.) LS1 shafts have broken on much less, time and again. That is anecdotal, though. And with significantly different power levels, a comparison of 3rd to 4th gen failures isn't valid.

Since you seem to have doubt, the best way to answer your already-answered question is to take 1 of each and cut them and validate wall thickness.

So where's your bandsaw?

 

Ha! I would totally cut some up if I had extras!!