3" v 3.5" driveshaft...what are you guys running with 1K+HP?

Done a search but looking for specifics.

Car is 3600lbs, street/strip, max 7-7200rpm, makes 800 hp / 770TQ N/A...may get sprayed with a 150-250 shot a bit later on.

Looking to go with a 3.5" CM driveshaft based on the MW calculations and a bit of overkill on the strength. Shaft length is to be 42" c to c.

Been thinking about Aluminum with my short overall shaft length - but not sure l have the room in a 4" OD shaft. Also, what would the 3.5" CM shaft be rated to HP/TQ wise in the 42" length ?

Any thoughts / recommendations would be much appreciated !

Thanx !

44" x 3.5" aluminum from Dyno-Tech. 9.03@149, 3350 lb
Doug

I run a 3" diameter steel driveshaft made by a local driveshaft shop w/ 1350 joints. I told tem what it was going in and that I wanted something that would last. Not sure how thick it is or exactly what material....all they told me is that it is a "thickwall" tube. Been in the car since 2008.
8.95 at 149.7 mph at over 3900 lbs.

Not saying a 3.5" shaft isn't better, b/c I'm sure it's stronger. Just showing what I've done w/ what I have.

Custom 3.5 inch CM drive shaft here, it was a little lighter than our stocker.

I went w/a 3 1/2" CM shaft based on a recommendation from Jason Pettis and the same one Douggie S. ran at that time and almost 14 years later, still kickin w/the same u-joints.......

Thanx fellas...

Chip Im surprised your running with a 3" DS at nearly 4K lbs and 1K+HP on the spray.

Thats a hell of a good Ds you have; is it chrome moly?

I have no idea, lol. Sheppard's Truck & Driveline Service in Florence, SC, made it for me.
It's one of those things that I had made in 2003 when the car was making about 600 hp and it's held up this long. That shaft got tweaked when the 727 exploded in 2008, so I had them make me another one just like it. No problems yet, but when/if it does break...I'll go bigger.

The "Wallace racing" web sight has a nice calculator that can guide you in the right direction. Also check out "Denny's Driveshaft " web sight. Ton of good info. I went with a 3.5" DOM shaft. It's long (45") in a heavy car that makes around 650HP. Shift at 7K. 1350 joints. No problems.

FWIW HP is part of the equation but more importantly is the drive shaft length and the intended DS RPM. Those will be the determining factors in what material and diameter you need In the end call the companies that make them and give them these details and they will tell you what you need.

Hi Al...given the shorter length a 3" might work but may not allow for growth. I was surprised Chip runs a 3" DS.

Having said that a 3" will work given my length and critical speed. But a 3.5" will allow for growth

I was kinda interested in what guys are running given their respective combos i.e."HP, TQ, weight, length and ,material.

BTT

Carbon fiber. 800ish HP 3000 lbs. Will be over 1000 HP if I ever turn on the bottle. I much prefer carbon fiber in case it ever breaks. The CF will just shatter and not beat the chassis to death.

I ordered a 3 1/2 " moly shaft last year about this time from Strange.........went through Cass ( Dr. Diff ) and it was a bargain with a capitol B.
Then had to send my Mark Williams slip yoke to Strange so they could balance it with the yoke.
First rate service and price all the way around.
I am all for overkill here.

Nobody else running an aluminum shaft? My cost from Dyno-tech was $440 w/ yoke. It's light and and critical speed is better than steel. No brainer in my book.
Doug

I ran a 3" driveshaft with my turbo wedge , have probable 100 runs over 200 MPH .

Once again it aint about power it about drive shaft speed, which is NOT engine RPM. I use MW stuff small 3.5" bonded aluminum shaft. Only omne time did I need more and that was with the 99 Hemi in the Cuda due to the length of the shaft and shaft RPM it required a carbon piece. Which I still have if anyone is looking for a smoking deal on one.

Read here if you want some more info.
http://markwilliams.com/driveshafttech.aspx

FWIW here is what critical driveshaft speed looks like. This is with a 4" aluminum shaft, not the vibration in the car down track. The aluminum shaft was fine with a 1050 hp motor due to downtrack driveshaft RPM. But with the 99 Hemi it was not so happy.
https://www.youtube.com/watch?v=OBUuEGlJ5ww

This is with a carbon fiber shaft and no other changes
https://www.youtube.com/watch?v=iBijNaRwePE