8hp70 driveshaft?

[Racer9]

I now have the 8hp70 trans, and am trying to get as many of the other incidentals as possible lined up.
What is the proper process for the driveshaft? I know it needs splines due to not having a slip yoke in the trans.
A new shaft is a little over $1k. I've found a used one for $500, but will keep looking. RCSB's aren't too common, so the shaft is hard to find.
Can I just have a spline installed on my current shaft?
What about a 2 piece shaft? They are more common and shortening one might be simpler, and less costly.
2wd truck so I'm not going to get a lot of up and down on the rear.

 

[Racer9]

Found a shaft from a 2017, same as trans is from, with 3.90 gears, mine are 4:11. Any reason it won't fit my 2011? Rear flange different?
I know they went to AAM axles, in what, '12?

 

[Pull Ya]

The RCSW 8 speed trucks have the reputation of throwing the drive shaft at around 100mph. I think that is why a lot of guys go to the 5" aluminum driveshaft. I think you're right, those are around a thousand bucks. I think Moe's sells them and I think he has a Xmas sale going for 10% off on some of his parts.
Jay

 

[Wild one]

Found a shaft from a 2017, same as trans is from, with 3.90 gears, mine are 4:11. Any reason it won't fit my 2011? Rear flange different?
I know they went to AAM axles, in what, '12?

Your 11 should have the later ZF diff,as they quit using the AAM diff in 2010. As Jay states the regular cab shortbox 2 wheel drives are famous for throwing the shaft at about 100 to 110 mph with 3.92 gears,with 4.11's you're gonna want to stay at about 95 to 100 mph to be on the safe side.
FYI when they do chuck the driveshaft,alot of times they'll break the transmission case and poke a hole in the gas tank,been a couple of the little 2wd RCSB's burn to the ground from the driveshaft exiting the truck.
If you had a 4X4 you wouldn't have any driveshaft issues,as they still use a normal driveshaft with a slip yoke into the transfer case.My little 4X4 has seen 155 mph and alot of runs well above 145 mph,and it's driveshaft never blinked.
BTW: your 4.11's are gonna be overkill with the 8 speed,you'll blow through 1st gear so fast,it'll basically be useless.
If it was my truck i'd hunt up a diff with 3.55's,as it's a good middle of the road gear ratio for the 8 speed in a light RCSB 2WD,and swap out your 4.11 diff.

 

[Sherman Bird]

Found a shaft from a 2017, same as trans is from, with 3.90 gears, mine are 4:11. Any reason it won't fit my 2011? Rear flange different?
I know they went to AAM axles, in what, '12?

"AAM" was, at one time, the vendor for GM for drivetrain components. Possibly others, but I do not know to a certainty. I've purposely used the brand over the years (They were NOT budget items back in the day), and cured more than a couple of "nightmare" situations where cheaper parts didn't make muster.
I'd like to think they are still the gold standard.