1 piece driveshaft in LWB

[ratrod67]

I need to get a driveshaft done for my 72 LWB Chevy. I'm running a 509 ci BBC and a T350 transmission. They guy that builds my driveshafts for me is telling me to get a 1 piece driveshaft. He says I will break the 2 piece shafts with my motor. I did the search here for info on the 1 piece in a LWB but it says driveshaft is not a valid search word. Should I get the 1 piece or not?

[bigjimzlll]

I went to a one piece with my LWB. I could not get a driveline shop to make one that was the needed almost 6 feet long. I moved the engine back 4 inches and used a th400 Long tail shaft tranny. This allowed me to use a 3.5" DOM shaft thats 59" long. Ofcourse I spin a lot of rpms...this is a determining factor on driveshaft length

[67k-20]

my 68 lwb had a factory 1-piece driveshaft. just incase you wanted to save some money.

[Maximum Overdrive]

What determines a one piece or two piece driveshaft is critical speed. Critical speed is the number of RPM's at which the shaft will explode.
Critical speed is related to weight, length, diameter, and the speed of the shaft. Longer shafts tend to be heavier and can come apart at highway speeds.

As far as I know most LWB trucks came with a two piece though some were known to have a once piece shaft but they tended to come with I-6.

[70rs/ss]

Originally Posted by Maximum Overdrive

What determines a one piece or two piece driveshaft is critical speed. Critical speed is the number of RPM's at which the shaft will explode.
Critical speed is related to weight, length, diameter, and the speed of the shaft. Longer shafts tend to be heavier and can come apart at highway speeds.

As far as I know most LWB trucks came with a two piece though some were known to have a once piece shaft but they tended to come with I-6.

In today's trucks they come with a one piece aluminum wrapped drivshaft yada yadda, but the technology can be implimented into our older trucks. I did a search for another member about an aluminum shaft and I can tell you if your shop can't or won't build one find another shop. If you have that kinda cash in a 509 don't think some 30-40 year old shaft will work, spend the $500-600 that it takes to have a custon shaft built for you and then you will not have to move the motor, nor will you have to be worried about driveshaft failure.

[76bonanza]

I have a custom made one piece in my truck only problem we had was with it lowered we had to modify the cross piece it goes thru in the rear. Dont have a price friend did it for me. I do have a th400 tho.

[davidh]

I think if the tranny was a long tail turbo 350 it wouldn't be a big deal.

[red71cheyenne]

I run a one piece in the 71 and only have issues of it hitting the crossmember on big bumps. Other than that its fine. Jeff. By the way, its 67.5 inches long.

[ratrod67]

Thanks for all the help. I'm not concerned with the cost. I get driveshafts made for $125 if I furnish the yoke. $150 if I don't. I was mainly concerned with tales of not being able to balance them right and whipping at high RPM. My truck is pretty low and I was also concerned about the shaft hitting the crossmember as said above. When I switched to BBC mounts from the SBC mounts it moved the motor and transmission back a couple inches. I had to drill holes to mount the transmission crossmember to the frame. It looks like it also made my stock driveshaft too long. The guy who does the shafts said he does 1 piece for the LWB trucks all the time but none for super high performance trucks. I just want it done right the first time.

[71Dragtruck]

Originally Posted by ratrod67

I need to get a driveshaft done for my 72 LWB Chevy. I'm running a 509 ci BBC and a T350 transmission. They guy that builds my driveshafts for me is telling me to get a 1 piece driveshaft. He says I will break the 2 piece shafts with my motor. I did the search here for info on the 1 piece in a LWB but it says driveshaft is not a valid search word. Should I get the 1 piece or not?

What is behind his thinking that you will break 2-piece shafts? I have a 2-piece 3" chrome alloy shaft running a custom steady, a splined back piece and 1350 u-joints. I was told the that I would break 1 piece shafts. I've had no problems so far, I'll see how it does behind my new mill this summer.

[bigjimzlll]

My local track really frowned on the 2 piece deal. I could'nt find in the NHRA rule book where it violated any rule though.

[ratrod67]

Originally Posted by 71Dragtruck

What is behind his thinking that you will break 2-piece shafts? I have a 2-piece 3" chrome alloy shaft running a custom steady, a splined back piece and 1350 u-joints. I was told the that I would break 1 piece shafts. I've had no problems so far, I'll see how it does behind my new mill this summer.

Not sure why he reccomended the 1 piece shaft. It's what he does for a living though. He's always done good work for me and is highly reccomended around here. He did the 1 piece shaft in my 67 SWB, Camaros and Chevelle. I just figured I needed the 2 piece shaft since it's a LWB truck. It surprised me when he said a 1 piece.

[corn]

A friend of mine told me that his dad put a suburban driveshaft in his 71. One piece & it bolted right in (he says). Was he blowing smoke up my tailpipe or can it be that simple?

[71Dragtruck]

I'm just kind of wondering, I went through the same thing, I wanted a 1-piece. I had mine done when I got it 4-linked, the place that did it said they built a 1-piece for a guy with a 84 Chev drag truck and he broke 2, so they built him one like they made me and it worked fine?

[71Dragtruck]

Originally Posted by bigjimzlll

My local track really frowned on the 2 piece deal. I could'nt find in the NHRA rule book where it violated any rule though.

Did they give you a reason? My track never said a thing about mine, I have 2 loops if that makes a differance.

[kbs71]

Check out this thread. I updated it about a year ago and haven't had any trouble with my 1 piece yet. One of the best $120.00 upgrades I've done.
http://67-72chevytrucks.com/vboard/s...d.php?t=131693

[ZOOMY]

For what it's worth, I have a '67 LWB GMC parts truck here with a factory 1 piece driveshaft, so the factory did it on some trucks..

[ratrod67]

Well, I got talked into the 1 piece driveshaft. Hopefully I'll get it in the truck and go for a spin this weekend.

[Longhorn Man]

A 2 piece would be stronger.
A center U joint is no weaker than the other 2 U joints, and the carrier bearing shouldn't be an issue either.

[jhow66]

Got a 502HO in my Cheyenne SWB with a T400 and 2 piece-no problems.

[Longhorn Man]

if they were so weak, they wouldn't be under trucks. period. I've seen street trucks doin 12's that has stock 2 pc driveshafts,
bug trucks with mega torque...... 3pce...4pce... even more on straight trucks.... never a problem.

[GloryHound]

Originally Posted by 71Dragtruck

Did they give you a reason? My track never said a thing about mine, I have 2 loops if that makes a differance.

2-loops make all the difference in the world to those guys. I've been hangin with a drag racing crowd and the track most of them go to and the class they are racing in says each drive shaft is required to have a loop. Also scatter shields are mandatory on stick shifts and highly recommended on automatics. Also the track has required most of them to install 8 pt. roll cages do to their speed.

Now these guys are driving Nova's and getting to right around 10 second times. Alot better than I ever intend to go since my car will be more street then strip, but safety features are always good things when you plan on going fast!