One-piece driveshaft DIAMETER

2013 4x4 double cab short bed. I have the stereotypical driveline vibe 5-10mph with a 2" AAL. I have read most of the pertinent information on one-piece driveshafts on this and other sites. What I haven't read about is what diameter one-piece driveshafts people are buying. Most look to be about 3" - 3.5".

I was talking to a reputable driveline shop here in Seattle and told him I want a one-piece with a double cardan off the tcase and a u-joint at the pinion. After measuring driveline dimensions he says, based upon my rear axle ratio (3.73) and tire size (265/70R17), that I need a steel driveshaft that is 4" in diameter. He says that a 3.5" will start to "jump rope" at ~80mph. A 4" will do the same but at ~90mph.

A couple issues with this:
1) If the driveshaft will disintegrate at ~80mph with my setup (which is a very common one) then nearly every guy that purchased a 3.5" Tom Woods driveshaft would be telling us about it by now.
2) I have not seen anyone one this site that has a single-piece driveshaft that is 4" in diameter. The one google image I found looked to be roughly 4" and it had grind marks where it touched the carrier bearing bracket.

Need some feedback from guys that have the one-piece driveshafts. What calculations did your driveline shop make about max speed vs diameter and why did they choose the size they did? Thanks for sharing your experience.

 

your driveline shop is not all that reputable if they are saying that crap

it is all about input and output angles not diameter of the shaft

bad angles are bad angles

https://www.youtube.com/watch?v=T4P75ZQvpws

 

Thread resurrection... Tom woods shop just sold me a 4" diameter drive shaft. Is no one really running such a shaft? If it's just clearance to the carrier I can probably take care of thst With a hammer and cut off wheel?

I have the Dakar leaf pack and shaft length measures 68.75" at ride height.

I tried to get drive lines Nw to repair my current shaft but they said it was too trashed and also that they wouldn't build a 1-piece shaft that long.

 

Good question. The one I got from Tom Woods was a 3.5" and mine was good till I regeared which causes the shaft to spin way faster to achieve the same highway speed. So even the 3.5" was good on stock gearing. That being said, 4" all the way if you can fit it.

Either shaft would require you to cut out the carrier bearing mount cross member. If it were me, I'd cut it in such a way that I could weld it back in later if needed. Realistically, you only need to cut it out if you plan on using all of your rear travel. On regular highway and city driving I can't imagine you'd use all the travel.

 

I was on the edge for 3.5" OD even with stock gearing and 32" tires, I definitely couldn't regear with the smaller shaft. Didn't think about that.

Thanks for the feed back didn't realize even the 3.5" would require cutting. I'll cut if the 1 piece does well at hwy speeds.

 

I just regeared to 4.56 gears and had the one piece 3.5" shaft. Couldn't go above 55mph without it vibrating like crazy. It was good prior to the regear. I was going to cut the cross member but decided I'd wait till after the regear; glad I did.

Currently having a two piece shaft made with a double cardan welded in after the carrier bearing. I think that SHOULD fix it and is the ideal solution. Check the other vibration thread in this section tomorrow when I get the truck back.

 

I just bolted my 4" woody in and it is so tight against the carrier bearing support that i'm going to cut it off in the morning. I've been researching this for months and i'm nervous about the cut but don't want my shaft all ground up.

 

Yep gonna have to cut!