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Recent threads on 1/2 shafts is interesting reading. Some things to remember, the shafts GM all had 1350 joints in them from 63-79. There were two shaft diameters used, 2.5" & 3" however the wall thickness wasn't the same. I covered this years ago but maybe some don't know.
2.5" had .120-125" wall
3" had 090" wall
Look to see what the aftermarket is selling.
Tom's 3.5" 134" wall 1350 or 1480 is what I use. In my opinion, they're the best. They are heavier for sure.
But here is the deal, the weak link is still the joint. We sheared Solid Spicer 1350 joints in half, both inner and outer, one dead hook. Bam - done, took out the shaft yoke too. The tubes were not damaged. Stepped up to 1480 and haven't seen that.....yet. In the same situation would an 083" tube or "HD" 090 tube have held up?
My physics math calculator says the 3" GM are maybe 20% stronger than the 2.5" GM. The extra diameter matters that much, GM used a thinner wall and they were still stronger. Imagine how much stronger the 3.5" Toms are with the even thick walls!
Steel H/S or Spicers will tend to bend a little before they break....but not much.
A stock BB with stock gearing, 2.5" shafts and solid spicers is pushing both of these near the limit of what they can handle.
My buddy twisted his GM 2.5" H/S with his ZZ427 BB, Tremec and 4:11 rear and fat Nitto tires. On the street. He was probably just one throttle drop away from breaking it all when he spotted it. It was just enough to change the camber.
I run 3.5"x.134" halfshafts custom made locally with solid Spicer 1480 joints. They've held up great so far! And yep they ARE heavy....but they haven't broke!
The specs of a 1480 u-joint say it would take 50% more TQ to break than a 1350.
A 500 ft lb big block stresses a 1350 pretty close to it's limit.
500 x 2.20 x 4.11 / 2 = 2260# , basically enough to permanently bend them, or worse. A clutch drop at full TQ with the sudden shock could be explosive.
A 1480 should work much better. It would almost laugh it off.
1/2 shafts
